Subscriber access provided by UNIV OF NEW ENGLAND ARMIDALE
Recent Advances of Structurally Ordered Intermetallic Nanoparticles for Electrocatalysis Weiping Xiao, Wen Lei, Mingxing Gong, Huolin L. Xin, and Deli Wang ACS Catal., Just Accepted Manuscript • Publication Date (Web): 06 Mar 2018 Downloaded from http://pubs.acs.org on March 6, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Recent
Advances
of
Structurally
Ordered
Intermetallic Nanoparticles for Electrocatalysis Weiping Xiao,a,1 Wen Lei,a,1 Mingxing Gong,a Huolin L. Xin,b Deli Wang a,* a. Key laboratory of Material Chemistry for Energy Conversion and Storage (Huazhong University of Science and Technology), Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, PR China Email:
[email protected] b
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973,
USA
ABSTRACT: Structurally ordered intermetallic phases have exhibited higher and higher electrocatalytic activity and stability than disordered alloys in many reactions such as the oxygen reduction reaction (ORR) and small molecule (hydrogen, formic acid, or ethanol) oxidation reactions. The enhanced electrocatalytic activity could be derived from the definite composition and predictable control over structural, geometric, and electronic effects. This review, based on the understanding of the catalytic mechanism of structurally ordered intermetallic nanoparticles, provides a comprehensive acknowledgement of how the particle size and morphology affect the catalytic performance. The strategy for reducing particle size and the impact of particle size on electrocatalysis will be firstly introduced. Then, recent developments in the synthesis and design of morphology-controlled catalysts are summarized. The structure-activity relationship between the catalytic activity and morphology including core-shell/hollow and porosity will be highlighted. Finally, the current challenges and future developments are provided. On the basis of this review, intermetallic nanoparticles will shed light on the future development of electrocatalysts for fuel cells and metal-air batteries. KEYWORDS: intermetallic compound, particle size, morphology, electrocatalyst, fuel cells 1. Introduction 1 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Proton exchange membrane fuel cells (PEMFCs) have attracted much attention for their highenergy conversion efficiency, high-energy density, environment friendly, and relatively low working temperatures.1,2 However, the widespread commercial applications of PEMFCs have been hindered by the exceedingly high costs of Pt-based catalysts.3 Typically, carbon-supported Pt-based catalysts, the only electrocatalysts presently used in applied PEMFCs, play a key role for catalyzing the sluggish kinetics of cathodic oxygen reduction reaction (ORR) and anodic oxidation of fuel (hydrogen, formic acid, or alcohol).4-6 At this juncture, how to enhance the fuel cell performance and reduce the loading of Pt are the essential subject of the current research studies7. In view of the above issues, researches on advanced Pt surface-enriched nanoparticles, replacing the Pt atoms with the less-precious metal (PdM@Pt, M@Pt), have aroused much attention.8 Recent research papers have been dedicated to enhance the performance of Pt-skin catalyst, but it is limited by the instable nature of the transition metal and Pd in the acid electrolyte.9 Another strategy is to alloy Pt with 3d-transition metals to form Pt-M alloy catalysts.10,11 The addition of an early transition metal to Pt could change the Pt 5d band vacancy, Pt-Pt interatomic distance and the number of Pt nearest neighbors, resulting in d-band center down-shift and changing the electronic structures of Pt12-16. The structural changes can affect the stability of reaction intermediates and the activation energy of a chemical reaction and then enhance the catalyst performance17,18. At the present stage of research, Pt-based alloy catalysts have attracted much attention, and more and more research works have been devoted to enhancing the catalytic activity and stability19-21. However, in these alloy phases, Pt and the secondary metal atoms are randomly distributed and the active sites are not structurally identical. Therefore, the corresponding catalysts would, to some degree, increase catalyst activity, but limited by the unsatisfactory durability due to the particle growth, 3d transition metal dissolution and corrosion of the carbon support at harsh operation environment. 22 Recently, atomically ordered intermetallic nanoparticles have attracted increasing research attention.23-25 Generally, the formation of intermetallic structure is highly dependent upon the composition and temperature. For example, the disordered face-centered-cubic (fcc) PtxFey nanoparticles are formed at a relatively lower temperature and can be converted to L12 ordered cubic Pt3Fe1, Pt1Fe3 and L10 ordered face-centered tetragonal (fct) Pt1Fe1 at higher temperatures.26 Moreover, the structure of an intermetallic compound is also relied on the 2 ACS Paragon Plus Environment
Page 2 of 41
Page 3 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
properties of transition metals and the interaction of the elements. Take Pt1M1 as an example, Pt1Fe1 can form L10 ordered fct structure, while Pt1Ni1 can form L10 ordered fct structure and L12 ordered fcc structure. And for the same transition metal of Fe, the formation temperature of L10 ordered fct-PdFe is lower than that of L10 ordered fct-PtFe and Pt1Fe3 can form L12 ordered intermetallic compound while Pd1Fe3 can not. For the conventional alloy catalysts, Pt and the secondary metal atoms are randomly distributed, while the ordered intermetallic nanocrystals have unique geometrical structure and local geometrical properties, providing precise control over geometric, structural. Hence, compared with disordered alloy surfaces, the stronger lattice strain of Pt on intermetallic surfaces could cause the d-band center shift and change the electronic effects of surface Pt, which make them exhibiting higher chemical/structural stability and activity.27-34 For instance, Sun and co-workers reported the structurally ordered PtFe exhibited enhanced ORR electrocatalytic active relative to disordered PtFe alloy35. Zou and coworkers studied the effect of structure transformation from disordered to ordered Pt3Cr catalyst on ORR activity and durability36. Although the mass activity on ordered Pt3Cr/C was slightly lower than the disordered Pt3Cr/C alloy nanoparticles, the Pt3Cr intermetallic nanoparticles displayed much higher stability. Recently, Pd-based intermetallic catalysts have also aroused some concerns37-43. Compared with disordered phase, ordered PdCu (B2-type) phases exhibited lower overpotential and higher oxygen reduction/evolution kinetic rate, which contributed to a remarkable enhancement in cyclic stability and an superior rate capability in Li-O2 battery44. Furthermore, ordered Pd3Fe intermetallic has been reported to exhibit significantly enhanced activity and durability toward ORR and Li-air full-cell cycling performance45. Compared with disordered phase, the ordered Pt (Pd)-based intermetallic catalysts are more stable and durable (Table 1). Therefore, it is essential to design intermetallic catalysts rendering them prohibitively durable. The catalytic performance on ordered intermetallic compound can be further enhanced by precisely tuning particle size, shape and morphology by controlling solvent, composition and heat treatment.53-55 Over the past decades, great efforts have been made to prepare size-dependent and morphology-induced intermetallic nanoparticle catalysts.56,57 This review, based on our studies, summarize the recent progress of ordered intermetallic compound, with controllable composite, size and morphology, for enhanced catalytic performance. The structure-activity relationship between the catalytic activity and morphology including coreshell/hollow and porosity will be highlighted to illustrate the potential of current developed 3 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 4 of 41
intermetallic compound catalysts for practical applications. The remaining challenges and future directions for rationally designing of efficient catalysts for fuel cells application were brought forward at the end. Table 1. The mass activity (MA) comparison on disordered and ordered intermetallic phase before and after durable test (ADT). MA-initial Catalyst Crystal phase
MA-ADT
A mgPt/Pd-1 A mgPt/Pd-1
Maintained Ref activity
D a -fcc c
0.34
0.17
50.0%
O b -fct d
0.51
0.41
80.0%
D-fcc
0.08
0.06
79.5%
O-fcc
0.17
0.15
85.9%
PdCoCu
O-bcc e
0.13
0.12
96.1%
Pt
D-fcc
0.10
0.15
47.4%
PdFe/Pd
O-fct
0.10
0.07
70.5%
Pt
D-fcc
0.11
0.08
69.6%
D-fcc
0.17
0.13
76.6%
O-fcc
0.24
0.21
86.5%
O-fct
0.23
0.21
91.0%
51
4.30
3.97
92.3%
52
PtFeCo
46
Pd3Pb
47
48
49
Pd3Cr
Pt3Fe2 PtPb a
50
O-hexagonal
D: disorder. bO: order. cfcc: face centered cubic. dfct: face centered tetragonal. ebcc: body
centered cubic.
2. Particle size controllable of intermetallic compound In general, the structure transformation from disordered alloy phases to structurally ordered intermetallic phases requires high temperature annealing (>500 °C), which inevitably leads to the aggregation of the nanoparticles as well as a dramatic increase in particle size and then affects 4 ACS Paragon Plus Environment
Page 5 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
catalyst activity.20,35,58,59. TaPt3 intermetallic nanoparticles were synthesized by annealing at 1000 oC and obvious agglomeration was appeared.60 The specific activity of the TaPt3 nanoparticles toward the ethanol electro-oxidation was three times higher than the Pt nanoparticles, but not for the mass activity. The agglomeration of particles hindered the ordered intermetallic compounds as high-activity catalyst applied in fuel cells. Hence, great efforts had been devoted to reducing intermetallic compound size and narrowing size distribution. Various strategies have been employed including carbon support,61-63 oxide coating,64,65 liquid phase synthesis and protective agents66-69, etc. Recent studies have shown that the ideal particle size forms spontaneously during the reaction process if and only if there is a good coordination of support, protective agents, composition and heat treatment temperature 70. 2.1 Carbon support Size-controlled intermetallic compounds could provide precise control over the local geometry and electronic structure. Under the circumstances, the shifts of the d-band center and the alter of adsorption energies may contribute to the modification of catalytic performance.71 Not only does the poisoning effect is largely relieved, but also the catalytic activity is enhanced.58 In the research of carbon-supported Pt-based (Pd/Ru-based) intermetallic catalysts, a larger number of research efforts have been concentrated on the interaction between PtM (PdM) and carbon support which affect the growth, structure, dispersion of nanoparticles and are interrelated to the PtM (PdM) nanoparticles size.72-74 It is known that carbon support could lower the Fermi level and increase the electronic density of Pt, which is conductive to the electron transfer and thus accelerate the electrocatalytic processes.75-77 An excellent catalyst support should enable rapid charge transfer and mass transport, be efficient in catalyst dispersion, capable of inhibiting agglomeration/coarsening and preclude catalyst dissolution during operation78. Due to their interpenetrating porous structures, high surface areas and narrow pore size distribution, ordered mesoporous carbon (OMCs) and modified mesoporous carbon (MPC) have been widely used as catalyst support. Ji and co-workers79 synthesized size-controlled Pt-Bi bimetallic nanoparticles embedded within the porous structure of ordered mesoporous carbon (OMC). By forming surface-modified OMC-S, the S acted as absorber and bound the metal precursors into the OMC, and simultaneously restricted the particle aggregation during reduction process (Figure 1a). Further 5 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
evidence was shown in HRTEM image which showed small particle size of 2.7 nm and homogeneous dispersion. The ordered structure, small size and the ‘ensemble effect’ make OMC-PtBi catalysts showed excellent catalytic properties for formic acid oxidation. Furthermore, OMC materials should have pore size over 10 nm and then can conductive to effective charge and mass transfer.80 Compared with OMC materials, ordered mesoporous carbon-silica (OMCS) composites have improved thermal and mechanical stability due to the coexisting silica species in the walls.81 Ordered, large pore (>30 nm) mesoporous carbon-silica (OMCS) as carbonsupport were reported by Shim’ s group.82 In detail, lab-synthesized amphiphilic diblock copolymers can conductive to the formation of uniform and large two-dimensional hexagonaltype pore structure, in which intermetallic PtPb are highly dispersed and smaller than the pore size, contributing to the desired triple-phase boundary (Figure 1b). The prepared PtPb exhibited lower onset potential and higher maximum power density toward formic acid oxidation relative to commercial Pt/C. The excellent performance can be ascribed to the combination of the highly dispersed support, significantly smaller size and stable intermetallic PtPb phase.
Figure 1. (a) The synthesis schematic of OMC-PtBi catalysts. Adapted with permission from reference 79. Copyright 2015 Nature. (b) The synthesis schematic of intermetallic PtPb containing OMCS. Adapted with permission from reference 82. Copyright 2015 American Chemical Society. 6 ACS Paragon Plus Environment
Page 6 of 41
Page 7 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
The modified mesoporous carbon (MPC), as previously reported, exhibits unique advantages, such as numerous small mesopores (2-3 nm), well-defined channels (5-6 nm) and large surface area in the pore wall of channel. It has been extensively used, via steric stabilization, to relieve the agglomeration of metal colloids. For example, Zhang and co-workers83 employed MPC-46 as a support to prepare well-dispersed PtBi intermetallic. On account of the abundant porous structure, PtBi nanoparticles displayed small particle size (3.1 nm) and narrow size distribution. During the last decade, graphene was regarded as ideal carrier owing to the excellent electronic conductivity, large surface area and low coefficient of thermal expansion.84 Graphene provided significantly higher active surface area and the synthesized intermetallic Ga-Pt particles embedment in graphene layers showed better ORR and MOR activity than that on Pt/C catalyst.85
2.2 Metal oxide and carbon coating The use of metal oxides and carbons as support/coating layer is another strategy to control particle size of structurally ordered intermetallic electrocatalysts.86-88 For example, the use of Al2O3, MgO and SiO2 has been shown to prevent nanoparticles from sintering at high annealing temperatures during the structural transformation from disorder alloy phases to ordered intermetallic phases.89-95 Kim, et.al demonstrated ferromagnetic Pt-rich fcc-FePt/Fe3O4/MgO nanoparticles with a one-pot reaction of Pt(acac)2 and Fe(CO)5 coated by a layer of MgO.90 The robust MgO coating prevented FePt nanoparticles from sintering at high annealing temperature, and thus the size of FePt (∼12 nm) in MgO shell had almost no change. Although nanoparticles coated with a layer of MgO can be stabilized against aggregation, it is difficult to transform from fcc to fct structure since the protection limited atom mobility within the MgO shell. Furthermore, based on this, Li’ group96 increased the ordering degree of the FePt particles by using a new strategy. The dumbbell FePt-Fe3O4 nanoparticles were firstly synthesized followed by the coating of MgO shell. The fully ordered fct-FePt structure was obtained by annealing the fccFePt-Fe3O4/MgO to reduce Fe and promote Fe, Pt diffusion within the MgO shell. Owing to the protection of metal oxides, the annealed FePt nanoparticles showed no aggregation and the size of the nanoparticles was 8.8 ± 0.5 nm. Compared with partially ordered FePt, the fully ordered fct-FePt nanoparticles exhibited higher ORR activity and durability without obvious Fe loss and nanoparticles degradation. Takahashi’ s group97 also prepared fct-FePt nanoparticles according to 7 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
the above mentioned method and subsequently coated by SiO2. Thermal diffusion of Fe and Pt atoms was confined inside the SiO2 nanoreactor during the heat treatment for the conversion from disordered to ordered phase. Thus, the average size of the FePt nanoparticles was estimated to be 6-7 nm, which was smaller than MgO-coated FePt nanoparticles. The metal oxide coated synthetic strategy is not limited to FePt, but can be applied to other intermetallic compound, providing a versatile approach to synthesize ordered intermetallic nanoparticles with relative smaller sizes and enhanced catalytic activity and stability.
Figure 2. (a) The synthesis schematic of ordered fct-PtFe phase with an N-doped carbon coating. (b-d) HAADF-STEM image of one fct-PtFe nanoparticle after annealing (b), a model structure (c), and a FFT pattern (d). (e) Mass and specific activities of Pt/C, fcc-PtFe/C, and fct-PtFe/C at 0.9 V. (f) LSV curves of fct-PtFe/C and Pt/C before and after durability test. (g) The maximum power density plots of fct-PtFe/C and Pt/C as functions of operating time. Adapted with permission from reference 98. Copyright 2015 American Chemical Society. 8 ACS Paragon Plus Environment
Page 8 of 41
Page 9 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
In addition, the use of N-doped carbon shells is a new and effective approach to prevent coalescence of nanoparticles. For instance, the fcc-PtFe nanoparticles were coated with polydopamine by a treatment with dopamine hydrochloride solution. Thermal annealing of dopamine-coated fcc-PtFe nanoparticles at 700 °C lead to the formation of atomically ordered fct-PtFe phase with an N-doped carbon coating (Figure 2a).98 Also, high angle annular dark fieldscanning transmission electron microscopy (HAADF-STEM) and fast Fourier transform (FFT) analysis (Figures 2b-d) confirmed the formation of ordered fct-PtFe structure. The 6.5-nm-sized fct-PtFe nanoparticles were close to the initial size of the fcc-PtFe, suggesting that the in situ formed carbon shell made the nanoparticles highly resistive to coalescence. The N-doped carbon shell also prevented the agglomeration and dissolution of particles during the harsh fuel cell operating conditions. By controlling the thickness of the shell below 1 nm, the fct-PtFe acquired excellent catalytic activity, which showed 10.5 times-higher specific activity and 11.4 timeshigher mass activity than commercial Pt/C catalyst (Figure 2e). Furthermore, accelerated stability test (ADT) and membrane electrode assembly (MEA) tests showed that ordered fctPtFe/C exhibited much higher long-term stability without significant activity loss relative to Pt/C (Figure 2f,g). Based on above analysis, the bimetallic ordered intermetallic phases have superhigh activity and durability than that of disordered phases, attributing to the ordered fct-PtFe structure and the presence of an N-doped carbon shell. Moreover, Arumugam99 studied the effect of Cu to the durability of ordered fct-PtFe catalyst toward the ORR. In detail, the ordered intermetallic fct-PtFeCu and fct-PtFe particles exhibited the similar mass activity and maintained about 70% and 40% of its initial activity after 10,000 cycles, respectively. Simultaneously, the STEM-EDX line scans proved that fct-PtFeCu catalyst showed a smaller degree of Fe and Cu dissolution, while fct-PtFe catalyst identified large dissolution of Fe, suggesting that the corrosion of Fe caused the collapse of ordered structure and bring about the poor durability. The superior durability of the ordered intermetallic fct-PtFeCu catalyst could be attributed to the ordered structure and synergistic effects of Cu presence. The smaller particles can also be prepared by using other metal oxides to prevent particles from sintering102,103. Owing to the thick SiO2 coating, the monodisperse L10-FePt nanocrystals were prepared at 900 °C without coalescence and coarsening.104 Furthermore, Qi and coworkers100 reported the synthesis of PtZn nanoparticles (3.2 ± 0.4 nm) on multi-walled carbon nanotubes (MWNT) via a sacrificial mesoporous silica (mSiO2) shell (Figure 3a) strategy. 9 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Figure 3. (a) The synthesis schematic of PtZn/MWNT@mSiO2. TEM images of (b) pristine MWNT, (c) Pt(OH)4/MWNT@SiO2, (d) Pt/MWNT@mSiO2, (e) PtZn/MWNT@mSiO2, and (f) PtZn/MWNT. (g) Mass activity and specific activity of different catalysts. Adapted with permission from reference 100. Copyright 2017 American Chemical Society. (h) HAADF-STEM image of fct-FePd/Pd-0.65 nanoparticles and the corresponding HAADF line profile. (i)LSV curves and (j) the corresponding mass activities for the C-fct-FePd/Pd-0.65 and C-Pt before and after durability test. Adapted with permission from reference 101. Copyright 2015 American Chemical Society. Pt(OH)4/MWNT@mSiO2 was prepared using the precipitation-deposition method followed by mSiO2 coating and H2 reduction to form Pt/MWNT@mSiO2 (Figure 3b-d). A Zn precursor was introduced into the Pt/MWNT@mSiO2 to form mSiO2-encapsulated PtZn alloy nanoparticles, 10 ACS Paragon Plus Environment
Page 10 of 41
Page 11 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
which can form the ordered PtZn/MWNT@mSiO2 at 600 °C annealing treatment (Figure 3e). Finally, the insulating mSiO2 shell was etched to test the PtZn/MWNT for electrocatalytic methanol oxidation reaction (MOR) (Figure 3f). The as-prepared PtZn catalyst exhibited smaller particle sizes and 10 times higher MOR mass activity in both basic and acidic medium relative to PtZn catalysts synthesized on MWNT without the mSiO2 shell (Figure 3g). The mechanism of MOR on PtZn catalyst, obtained from density functional theory (DFT), go through a “non-CO” pathway because the present of Zn atoms can stabilize the OH* intermediate, while pure Pt system forms highly stable COH* and CO* intermediates, causing poison of the catalyst. Moreover, the calculation results indicate that the MOR catalytic reaction is favorable to occur on smaller particles for the sake of the lower-lying energetic pathway and higher density of corner sites. Based on the above analysis, smaller PtZn nanoparticles could increase the number of the active sites and then enhance the MOR activity relative to larger ones. The strategies of metal oxides and carbon as supports/coatings are not limited to Pt-based nanoparticles, but can be extended to Pd-based intermetallic compound nanoparticles, providing a versatile approach for the synthesis of structurally ordered Pd-based nanoparticles with enhanced electrocatalytic activity and stability.105-111 Sun and co-workers112 synthesized urchinlike FePd-Fe3O4 nanocomposites, which can convert to the L10-ordered FePd-Fe intermetallic nanoparticles. In a later time, they reported core/shell fct-FePd/Pd nanoparticles via reductive annealing of core/shell Pd/Fe3O4 nanoparticles followed by temperature-controlled Fe etching in acetic acid
101
. The high-angle annular dark field (HAADF)-STEM image (inset of Figure 3h)
and the HAADF line scan profile of the fct-FePd/Pd-0.65 nanoparticles (Figure 3h) confirm the formation of the Pd shell and the intermetallic FePd core. Core/shell FePd/Pd nanoparticles with the shell thickness of 0.27, 0.65 and 0.81 nm were obtained and fct-FePd/Pd-0.65 nanoparticles had the most efficient ORR activity. More importantly, the fct-FePd/Pd-0.65 nanoparticles exhibited the similar activity and durability with C-Pt (Figure 3i, j). This excellent ORR catalytic performance was derived from the optimal lattice compression of Pd in the 0.65 nm Pd shell affected by the fct-FePd core according to the DFT calculations. This work demonstrates a new way of tuning Pd lattice and helps to develop Pd-based electrocatalysts in acid media. 2.3
Protective agents and other methods
11 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
It is essential to develop effective strategy for the synthesis of intermetallic nanoparticles with smaller size at low temperature. Liquid phase reaction is the best choice.113,114 According to classical nucleation theory, in order to obtain size-controlled intermetallic catalysts with small size and high catalytic activity, knowledge and/or control of the reaction temperature, surface free energy and the use of monodispersed and homogeneous precursors are particularly important115-117. For instance, the linear polymer poly (N-vinyl-2-pyrrolidone) (PVP) has been utilized as an effective protecting agent against the agglomeration of metal colloids by forming complexes with metal ions via coordination.118,119 Sra and co-workers synthesized atomically ordered AuCu and AuCu3 nanocrystals at relative low reaction temperatures by using PVP as the stabilizer. The ordered AuCu and AuCu3 can be further redispersed as discrete colloids in solution for high-volume applications, which is almost impossible after annealing at higher temperature.120 Xia’s research group employed PVP as a stabilizer for the synthesis of PtBi2 intermetallic nanoparticles with the size of about 4.1 nm. The small particle size and intermetallic structure contributed to the remarkable enhancement of ORR activity with a methanol-tolerant property.121 Recently, to control the size of the Pt-Bi intermetallic nanocrystals, the solvents and the length of the reaction channel were modified in microfluidic reactors as shown in Figure 4a122. The special synthesis strategies can accurately control reaction temperature to tune the singe-phase Pt1Bi1 and Pt1Bi2 intermetallic nanoparticles. The Pt1Bi1 intermetallic nanoparticles were uniform V-shaped nanorods and possessed a super-lattice diffraction (100) crystal plane, while the Pt1Bi2 intermetallic nanocrystals were nano-spherical morphology and possessed a super-lattice diffraction (001) crystal plane. The presence of Bi on Pt is conducive to preventing the formation of intermediate products during MOR. Hence, the asprepared Pt1Bi2 intermetallic catalyst possessed excellent methanol tolerance. In another study, Howard123 reported that the size (under 3 nm) of fcc-FePt particles could be controlled by solvent type, concentration of surfactants and stabilizers, heating temperature and purification process. More importantly, PtFe catalyst with the fct structure could be obtained directly without the need of high temperature annealing, where sintering might occur, and this was attributed to the use of nonadecane as stable solvent. Another interesting discovery is that the presence of Au can facilitate the FePt structure transformation from fcc to fct FePtAu nanoparticles. Fct-FePtAu were synthesized by co-reduction method with oleylamine and tetradecylphosphonic acid as stabilizer.124 High-temperature annealing was operated to convert the fcc-FePtAu to fct-FePtAu 12 ACS Paragon Plus Environment
Page 12 of 41
Page 13 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
and remove the surfactants (Figure 4b). The fcc FePtAu nanoparticles are obtained at 400 °C, while the fct-FePtAu structure is formed at 600 °C, the, with Au segregating on the nanoparticle surface.
Figure 4. (a) TEM images of Pt1Bi2 intermetallic nanoparticles. The inset shows schematic of microfluidic reactor system. Copyright 2015 American Chemical Society.122 (b) The structural change schematic of the FePtAu nanoparticles. Adapted with permission from reference 124. Copyright 2012 American Chemical Society. (c) The structural change schematic from PdCu A1 to PdCu B2. (d) TEM image of PdCu nanoparticles. The inset shows specific activities for the ORR catalysts. Adapted with permission from reference 125. Copyright 2016 American Chemical Society. Wet-chemistry methods have received increasing interest for the preparation of well-dispersed intermetallic nanocrystals at relatively low temperatures. For instance, PdCu, PdCuNi, and PtCuCo nanoparticles were prepared by a wet-chemical method in the presence of stabilizers.48 The monodisperse PdCuM particles could be transformed into ordered intermetallic phase during 13 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
annealing treatment at 375 oC. By precise control the composition and intermetallic phase, the ordered PdCuCo nanoparticles exhibit most excellent ORR and OER activity and stability. The DFT calculation results further indicated that the enhanced performance derived from the ligand effect and the compressive strain on the Pd surface caused by the smaller Cu, Co and Ni atoms. Partially ordered palladium-copper (Pd-Cu) nanoparticles had been synthesized by Kariuki and showed high ORR activity in acidic electrolyte.126 In a later study, Wang and co-works solved this problem and synthesized fully ordered PdCu B2 phase transformed from disordered A1 phase by a seed-mediated co-reduction route (Figure 4c). This method afforded the ordered PdCu nanoparticles of high monodispersity (Figure 4d). The monodispersed PdCu B2 nanoparticles were highly suitable for structure-activity studies and the ordered nanoparticles exhibited superior ORR performance relative to disordered PdCu A1 nanoparticles (inset in Figure 4d). Furthermore, ordered intermetallic Pd2Ge phase was synthesized by using a solvothermal strategy and the reaction time was varied to control the size of the nanoparticles.127 The Pd and Ge atoms occupy two different crystallographic positions with a vacancy in one of the Ge sites. The order of activity toward electrochemical oxidation of ethanol was Pd2Ge_36 > Pd2Ge_24 > Pd/C. The increase in the catalytic activity for the Pd2Ge_36 sample was due to the dealloying effect with the evolution of a small amount of Pd, which outweighed the presence of localized defects in the Pd2Ge_24 sample. Moreover, bordered Pd2Ge nanoparticles can also be regarded as a model system where a perfect balance between the adsorption energies of CH3CO and OH on the catalyst surface dictates its electrocatalytic activity and the presence of vacancies in the inactive sites undoubtedly affects the course of reactivity. In addition to the study of homogeneous systems, water-in-oil (w/o) microemulsions are also widely employed for controlling particle size.130 The reducing agent is dissolved in the oil phase of a w/o-microemulsion, while the metal salt is solubilized in a second aqueous phase. The reaction occurred at the water-oil interface and then the morphology and size of the nanoparticles can be controlled by varying the composition and temperature of the microemulsion. Magno’s group131 prepared PtPb intermetallic nanoparticles (3-6 nm) by controlling the reducing agent and metal salts in the w/o-microemulsion. The results indicated that the aqueous phase had little influence on the composition of the nanoparticles, while it indeed affected the size of the resulting nanoparticles.
14 ACS Paragon Plus Environment
Page 14 of 41
Page 15 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Figure 5. (a) The synthesis schematic of Pt3Fe intermetallic nanoparticles. (b) XRD patterns of all four samples. (c) A model ADF-STEM image of an ordered Pt3Fe particle along the [100] axis. Adapted with permission from reference 128. Copyright 2012 American Chemical Society. HRTEM images of Pt3Ti/C (d) and its corresponding FFT image of the atomic arrangement (e). HRTEM images of Pt3V/C (f) and its corresponding FFT image of the atomic arrangement (g). (h) LSV curves of Pt/C, Pt3V/C, Pt3Ti/C catalyst. Adapted with permission from reference 129. Copyright 2014 American Chemical Society. There are some other methods to control the particle size and thus increasing the intrinsic electro-catalytic activity and stability. For instance, the microwave assisted method is conductive to the formation of monodisperse fcc FePt nanocrystals which could be transformed into the fct phase at relative low temperature of 364 oC
132
. Both of intermetallic AuCu3/C and AuCu/C
particles with a narrow size distribution of 3 nm could be preprared by a sonicate function method using high viscosity viscose of ethyleneglycol as solvent. The small AuCu3/C and AuCu/C exhibited advanced ORR catalytic activities performance, which could be mainly attributed to the synergetic effects of electro-active atomic Au and Cu on the particle surface, in which Cu helps to activate the O2 molecule and Au benefits OH− desorption.133 Furthermore, they investigated that synergetic effects existing among the Au and Cu atoms instead of Au-Au or Cu-Cu site are conductive to oxygen reduction reaction through DFT calculation.134 Mun’ s group135 tuned the particle composition, size and intermetallic crystalline structure of nanoalloys 15 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
by highly specific, simultaneous deposition of multiple metal precursors within uniform selfassembled nanodomains in BCP thin films. Higher annealing temperature and longer annealing time are favorable for the formation of the ordered phase. However, the long-time annealing promotes the sintering of nanoparticles. To maintain a small particle size, a practicable strategy is to increase the annealing time at temperatures below the melting point of KCl136,137. In this case, KCl, an encapsulant, can preclude/prevent the agglomeration of nanoparticles during thermal annealing (especially for the generation of ordered intermetallic phases).138 Generally speaking, precisely tuning the concentration of the KCl can control the particle size. To study the effect of the concentration of the KCl to particle size, Chen128 developed a surfactant-free nanoparticle-KCl matrix method for the synthesis of Pt3Fe intermetallic nanoparticles with controlled size and structure (Figure 5a). Compared with the disordered alloy phases, the appearance of super lattice peaks of (110), (210), and (211) can be verified from XRD patterns, demonstrating that the desired ordered Pt3Fe intermetallic phase was fcc-ordered (Figure 5b, c). Also, by controlling the amount of KCl, the Pt3Fe intermetallic nanoparticles exhibit different average particle size of 2.5, 4, and 20 nm, respectively. Furthermore, the Pt3Fe nanoparticles could be released from the salt and then load on the carbon black support with little agglomeration. The 4-nm Pt3Fe nanoparticles exhibited an enhanced ORR efficiency relative to Pt/C. The excellent performance originated from the ordered intermetallic phase of the core in the resulting core-shell particles. Moreover, the similar NaCl-Type strategy can also be used for the synthesis of FePt-MnO binary nanocrystal.139 The constituent FePt nanocrystals can be transformed into the L10 ordered phase with almost no degradation, while FePt-only and FePtMnO disordered nanocrystal exhibited substantial sintering during annealing at 650 oC. This strategy could be conveniently extended to the formation of other ordered phase such as CoPt3 and FePd140,141, opening a new and general route to the fabrication of highly ordered 2D ferromagnetic nanocatalyst arrays. More recently, Cui and co-workers129 employed KCl as the encapsulant in combination with THF to prepare a series of structurally ordered Pt3Ti and Pt3V particles with small size. To visualize the ordered structure from the atomic level, HR-TEM were studied and showed the unique super-lattice diffraction peak, which was not present in the disordered alloy phase (Figure 5d-g). They also found that particle size and distribution can be controlled by tuning the annealing conditions and the density of nanoparticles in the KCl matrix. The present of KCl matrix can greatly reduce the coalescence of nanoparticles during thermal 16 ACS Paragon Plus Environment
Page 16 of 41
Page 17 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
annealing, which ultimately controlled the particle growth processes and consequently yielded nano-catalysts of deliberately controlled size. Furthermore, the nanoparticles could be released from the salt in an ethylene glycol-water solvent mixture and then uniformly load on the carbon black support with minimal agglomeration. For methanol oxidation, ordered Pt3Ti/C and Pt3V/C exhibited improvement in activity and durability compared with Pt/C (Figure 5h). Pt3Cr ordered intermetallic phase had been studied comprehensively by controlling ordering degree and particle size using a KCl-matrix method.50 Such structurally ordered Pt3Cr/C exhibited superior ORR kinetics relative to disordered PtCr alloy phase and commercial Pt/C. More importantly, after four weeks of chemical stability testing, a minimal leaching loss of Cr was observed and the ordered structure was still preserved. The enhanced activity and durability of the ordered Pt3Cr/C can be ascribed to its ordered crystal structure and small particle size. This work provides a guide to optimizing the synthesis of ordered intermetallic catalysts with enhanced catalytic performance.
3. Morphology controllable synthesis As is well known, a number of electrocatalytic reactions are structure-sensitive. Thus, it is essential to fundamentally understand the relationship between the morphology and electrocatalytic properties. Closely controlling the reaction parameters can be used to precisely control nanoparticle composition, microstructure and properties, which can, in turn, increase the density of active sites and, consequently, enhance the catalytic activity and stability of electrocatalysts. 3.1 Core-shell nanoparticles To maximize the utilization efficiency of Pt and enhance catalytic activity, core-shell structure nanoparticles with one to two layers of Pt on the surface of metal-alloys have aroused much attention142,143. One of the most promising methods is to synthesize core-shell structures, which is to put Pt atoms only on the catalyst surface or to tune the distance of atoms, leading to the shift of the d-band center to be more catalytically efficient.9,144,145 Core-shell structure catalysts, consequently, can not only reduce the platinum content but also usually exhibit excellent performance relative to monometallic Pt.49,146,147 Wang and co-workers148 designed and studied the Pt-skin nanoparticles by a combined experimental and computational method. In detail, 17 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
structurally ordered AuCu intermetallic compounds were firstly synthesized, and then a Pt skin was decorated on the surface of AuCu. Combined with DFT calculations, they found that 1-2 monolayers of Pt skin on AuCu intermetallic surface exhibited the best ORR activity. The enhanced ORR performance can be ascribed to the synergistic effect of the intermetallic cores and unique Pt monolayer. Furthermore, a Pd skin on AuCu intermetallic nanoparticles is controllably fabricated and exhibit excellent electrocatalytic ORR activity. The excellent performance is originated from shrink strain of Pd lattice caused by AuCu intermetallic core.149 Ghosh’ group150 explored the electrocatalytic properties of core-shell structure nanoparticles with PtPb, PdPb, and PdFe intermetallic compound core and PtML shell. The strain effects and electronic interaction between the Pt monolayer and the substrate can cause the shift of d-band center and thus the produced electrocatalysts have high activity, low metal content, and high stability. In addition to non-Pt intermetallic core151, the establishment ordered Pt-based intermetallic compound is highly necessary for the development of high performance electrocatalyst. Liu’ group152 compared the stability of alloy and intermetallic PtSn nanoparticles with the same size and composition. They considered that the intermetallic PtSn exhibited superior activity and stability compared with the disordered PtSn. Furthermore, the intermetallic PtSn could be transformed into core-shell structure PtSn@Pt particle via a potential cycling process and showed significantly enhanced CO-tolerance relative to commercial Pt and E-TEK PtRu nanoparticles. They believed that the superior CO-tolerance of the PtSn@Pt nanoparticles can be ascribed to the electronic effect between PtSn core and the Pt shell. As for the core-shell nanostructures, to further examine the relationship between lattice strain and electrocatalytic performce, Botton’s group51 studied the intermetallic core-shell structure PtFe catalysts with ordered Pt3Fe2 core encapsulated within a bilayer Pt-rich shell. The STEMHAADF image of intermetallic Pt3Fe2 nanocatalysts showed alternating dark and bright intensities for Fe and Pt atomic columns, respectively (Figure 6f). The three-dimensional model of one particle was presented in Figure 6g. The STEM-HAADF images demonstrated that the Pt3Fe2 nanocatalysts exhibited a non-uniform strain distribution on a 2D-projected plane rather than a uniform single strain value. This was because the Pt atoms on the surface were slightly relaxed compared to the bulk of the nanoparticle. Based on calculations, the lattice strain of the bulk Pt3Fe2 nanocatalystswas determined to be about -3% relative to pure Pt/C (Figure 6i, j), which lead to an increase in mass activity (228%) and enhanced specific activity (155%) for the 18 ACS Paragon Plus Environment
Page 18 of 41
Page 19 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
ORR when compared with Pt/C (Figure 6h). More importantly, after potential cycling durability tests, there was a minimal decrease (9%) in catalytic activity and the Pt shell suffered a continuous enrichment on the ordered Pt3Fe2 core. Furthermore, Liu and co-workers compared the stabilities of core-shell intermetallic and alloy PtSn catalysts with the same size and composition. The ordered PtSn intermetallic exhibited an enhancement in stability and activity compared with the PtSn alloy, which can be attributed to the lattice contraction of Pt shell caused by the ordered PtSn core.152
Figure 6. (a) ADF-STEM image of Pt3Co/C-700. (b) Diffractogram of the center particle in a. (c) The idealized structure of the Pt3Co particle. Multislice simulation of (d) disordered alloy Pt3Co and (e) L12 ordered intermetallic Pt3Co. Adapted with permission from reference 153. Copyright 2013 Nature. STEM-HAADF images (f) and the idealized model (g) of Pt3Fe2 IMCS nanocatalyst. (h) The mass activity and the specific activity of Pt3Fe2 relative to Pt/C. (i) STEMHAADF images of Pt3Fe2 and its two-dimensional percentage relaxation mappings (j). Adapted with permission from reference 51. Copyright 2013 American Chemical Society. 19 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Recently, highly uniform PtPb/Pt core/shell nanoplates have been synthesized to promote the enhancement of ORR performance.52 Rather than using compressive strain to optimize the oxygen adsorption energy, Bu and co-workers show that a very high tensile strain can also exhibit the superior ORR electrocatalytic activity. The as-prepared PtPb@Pt hexagonal nanoplates showed intermetallic PtPb phase with monodisperse edge length of ~16 nm (Figure 7a). The HRTEM image indicated that crystalline structure of the interior is different from the edge, contributing to relax the misfit strain between the edge phases (Figure 7b). Thus, two types of interfacial planes formed in PtPb nanoplates: {001}PtPb//{110}Pt between PtPb and top (bottom)-Pt layer and{010}PtPb//{110}Pt between the PtPb and the edge-Pt layer (Figure 7c,d). The unique Pt {110} crystal surface is conducive to the improvement of ORR activity since
Figure 7. (a) TEM image and (b) HRTEM of hexagonal nanoplate. (c, d) The schematic models of the nanoplate. (e) ORR polarization curves and CVs of different catalysts. (f) The changes on specific and mass activities of the PtPb nanoparticles before and after different potential cycles. Adapted with permission from reference 52. Copyright 2016 Science. TEM images (g) and HRTEM images (h) of PtPb1.12Ni0.14 octahedra. (i) Schematic representation of the ORR on PtPb/PtNi octahedra. Adapted with permission from reference 154. Copyright 2017 American Chemical Society. 20 ACS Paragon Plus Environment
Page 20 of 41
Page 21 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
the Pt {110} facet is more active than Pt {111} facet for the ORR in perchloric acid. DFT results indicate that the large tensile strains on the top (bottom)-Pt and edge-Pt (110) facets may conductive to optimize the Pt-O bond strength. Hence, the PtPb nanoplates exhibited super high ORR performance relative to PtPb/Pt nanoparticles and Pt/C (Figure 7e). The PtPb/Pt nanoplates with intermetallic core and uniform four layers of Pt shell can undergo 50,000 voltage cycles with negligible activity decay and no obvious composition and structure changes (Figure 7f). In a later report, they demonstrate the intermetallic Pt-Pb-Ni octahedra with well-defined morphology, composition, and size (Figure 7g)154. The PtNi shell thicknesses were calculated to be around 0.8 nm for the PtPb1.12Ni0.14 octahedra (Figure 7h). Those nanostructures with unique intermetallic core, active surface composition and the exposed facet, exhibited superior ORR activities than the Pt/C (Figure 7i). Recently, new advances in forming intermetallic compounds with CO-tolerant have been reported155. Pb, a promising alloying element or ad-atom, has attracted extensive interests due to their applications to enhance CO-poisoning tolerance and formic acid oxidation activity. Kang’s group156 synthesized of intermetallic Pt3Pb nanocrystals. The activity are further enhanced by forming Pt3Pb@Pt, which may be derived from continuous decreases of dehydrogenation barriers, strong adsorption of reactant molecules, and, most importantly, the suppression of the formate path and avoidance of stable for mate intermediates. Nevertheless, the activity decreases with further increase of the Pt ratio due to CO* poisoning caused by structural relaxation of the extra Pt atoms. In addition, the non-precious core-shell structure CoTi@CoTiO3/C catalyst with intermetallic CoTi core and CoTiO3 shell is reported and shows superior ORR catalytic performance, which can be ascribed to the surface oxide layer polarization effect caused by the intermetallic CoTi core.157 3.2 Hollow, porous and shape-controlled structures Controlling nanoparticle morphology is a critical issue to the improvement of catalytic activity and stability158-160. Many strategies have been conducted to prepare specific morphologycontrolled nanoparticles such as hollow-structures, nanowires, porous-structures and polyhedronstructures161-165. Recent studies have shown that different morphologies can be formed spontaneously during the leaching of Pt-based nanoparticles166. In addition to increasing surface area, dealloying can influence particle morphology, surface strain, which may affect the ORR 21 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
activity and stability of the resulting nanoparticles. For instance, Lang167 presented a novel class of mesostructured Pt-Al catalysts with Pt3Al intermetallic compound skeletons and atomic layerthick Pt skins through dealloying of uniform α-Al metal and Pt8Al21 alloy intermixture. The thickness of the ribbon was reduced and the bimodal MP architecture with quasi-periodic Pt3Al/Pt ligaments and MP channels were formed. The fcc L12 ordered intermetallic Pt3Al catalyst could be directly identified from HAADF-STEM image along the [001] zone axis, where a periodic square array of pure Al columns (low intensity) was surrounded by Pt columns (high intensity) at the edges and corners of each unit cell. The XRD pattern further verified the super ordered structure, which would lead to a lower d-band center for the strain effects and then weaken the adsorption of oxygenated species and resulted in a 6.3 fold enhancement in the ORR specific activity.
Figure 8. (a) BF-STEM images and EELS mapping of Cu3Pt/C nanoparticles after electrochemical dealloying. (b) BF-STEM images and EELS mapping of Cu3Pt/C after chemical dealloying. (c) Mass and specific activities for ORR comparison of Pt/C, Cu3Pt/C, Cu3Pt/Celectrochemical dealloying and Cu3Pt/C-chemical dealloying. Adapted with permission from reference 168. Copyright 2015 American Chemical Society. (d) ADF-STEM images of Cu3Pt/C nanoparticles after different stability test condition. (e) ORR polarization curves and (f) mass and specific activity for ORR comparison of Cu3Pt/C after 5000 (5K) and 100000 (100 K) potential
22 ACS Paragon Plus Environment
Page 22 of 41
Page 23 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
cycles. Adapted with permission from reference 169. Copyright 2015 American Chemical Society. Although the research of dealloying on Pt-based alloyed materials has attracted much concern, the attention has been focused on disordered alloyed phases in which the constituent atoms are randomly scattered. However, relatively few efforts have been devoted to the ordered intermetallic Pt nanoalloys. In this context, we have systematically studied the electrochemical and chemical dealloying of structurally ordered intermetallic Cu3Pt/C on the ORR activity.168 Electrochemical dealloying was performed by potential cycling between 0.05 V and 1.0 V in 0.1 M HClO4 at a scan rate of 50 mV s-1. Chemical leaching was conducted by immersing the catalysts in 1 M HNO3 under magnetic stirring at 40 oC for two days. We found that electrochemical dealloying lead to the formation of an ordered Cu3Pt core structure with a thin Pt shell (Figure 8a), while chemical leaching gave rise to a “spongy” structure with almost no ordered structure preserved (Figure 8b). Both leaching strategy resulted in an enhancement in ORR specific and mass activities (Figure 8c). To further examine the correlation between morphology of ordered Cu3Pt/C intermetallic and electrocatalytic activity, we performed an in depth study on the morphology by electrochemical dealloying methods, using scanning transmission electron microscopy.169 Different scan rate and scan potential range may lead to varies morphology and thus resulted in different catalytic properties. As shown in Figure 8d, the Cu3Pt/C ordered intermetallic nanoparticles exhibited a uniform elemental distribution of Pt and Cu, while electrochemically dealloying at a scan rate of 50 mV s-1 for 5000 cycles between 0.05 and 1.0 V in a N2-saturated 0.1 M HClO4 formed a 0.6-1.0 nm thickness of the Pt skeleton layer on the surface of the nanoparticles. The morphology of the particles was changed to cubic as the scan rate increased from 50 mV s-1 to 1 V s-1 during the same cycling time. When increased the upper limiting potential to 1.2 V at a sweep rate of 50 mV s-1 for 5000 cycles, the morphology of the particles turned out to be hollow structure. Moreover, by applying a constant potential of 0.8 for 3 h, only a small fraction of the particles formed porous structures. When the potential was held at 1.0 V, the majority of particles presented dark spots in the ADF-STEM image, corresponding to internal voids or empty space within the particle. Notability, porous morphologies and core-shell structure can band together to achieve the excellent ORR activity (Figure 8e, f). It had been well established that the ordered intermetallic phase had positive effect on enhancing the ORR activity. 23 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Figure 9. (a) HAADF/STEM images of shell-ordered and disordered nanoparticles. (b) Simulated ordered particle at the tipping point of pore creation and disordered particle with developed porosity. (c) STEM image and simulation of 12 h acid treated particles. Adapted with permission from reference 170. Copyright 2016 American Chemical Society. The atoms in the ordered phase occupy well-defined positions and unique strain interactions, which would change the d-band center and contributed to the enhancement of electrocatalytic performance. However, how to understand the relationship between selective leaching of the less noble metal and long-term ORR performance, on the atomic scale, is still absent. Pavlišič170 intensively studied the dealloying of intermetallic PtCu3 by advanced characterization techniques and kinetic Monte Carlo simulations. HAADF/STEM images of the ordered and disordered PtCu3 particles are shown in Figure 9a. Unlike the case in disordered alloys, in the ordered counterparts the atoms of different components occupy well-defined positions. The dissolution experiment of the PtCu3/C catalyst (ordered or disordered) with identical initial compositions and particle size distributions was soaked in 0.1 M HClO4 and the leached copper was monitored using ICP-MS. The result demonstrated that the copper leaching rate of disordered and ordered phase were approximate, whereas morphological and structural exhibited significant differences (Figure 9b,c). The ordered particle displayed larger pores and a lower number of pores relative to disordered particles after acidic treatment. HAADF/STEM and ESA measurements together with 3D kinetic Monte Carlo simulations revealed the formation of a smoother and “skin-like” surface 24 ACS Paragon Plus Environment
Page 24 of 41
Page 25 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
on the ordered sample (Figure 9b). The unique of structural and morphological on ordered sample give a reasonable explanation for the enhanced ORR activities relative to the disordered nanoparticles.
Figure 10. a, d, g) HAADF-STEM, b, e, h) atomic-resolution HAADF-STEM images taken from the yellow region boxed in HAADF-STEM image, and enlarged images of four corners of c) cubic, f) concave cubic, and i) defect-rich cubic intermetallic Pt3Sn nanocrystal. Bottom-left and top insets in (b, e, h) are the crystal structures images of intermetallic Pt3Sn and corresponding 25 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
FFT patterns from b) [110] and e and h) [100] view directions. (j) CVs of formic acid oxidation. (k) Loss of peak current density as a function of cycling numbers. Adapted with permission from reference 173. Copyright 2016 Wiley. Constructing surface defects is conductive to enhance the catalytic activity and stability on intermetallic materials. However, it is still a technological challenge to prepare stable catalyst with defect-rich surface. Sun and co-workers reported that the cube-like particles may induce self-assembled super-lattice (100) arrays, while polyhedron-like particle produce super-lattice (110) arrays.171 This indicated that the particle structural alignment can be tuned by controlling the shape of the nanoparticles. To this end, FePt nanocubes were prepared by tuning the addition sequence of the stabilizers and Fe/Pt ratio in the precursors, which creates a (100) textured array. 172
In a recent report, Hongpan Rong173 proposed a kinetically etching strategy for the synthesis
of cubic, concave cubic, and defect-rich cubic intermetallic Pt3Sn nanocrystals, which can be directly observed In HAADF-STEM images since the brighter areas indicate thicker atomic layers and the darker areas are depressions (Figure 10a,d,g). The defect-rich Pt3Sn nanocrystals have the most complicated surface structure among three kinds of cubic Pt3Sn nanocrystals. The atomic-resolution HAADF-STEM image of cubic (Figure 10b), concave cubic (Figure 10e) and defect-rich cubic (Figure 10h) Pt3Sn nanocrystal were projected from the [110], [100] and [100] direction, respectively. The atoms can be distinguished since the intensity of one Pt atom is higher than that of one Sn atom. The structure of intermetallic cubic Pt3Sn exhibited the (110) plane with alternate stacking of Pt and Sn atoms, while concave cubic, and defect-rich cubic Pt3Sn showed (100) plane with alternate stacking of full Pt and Pt-Sn alternately, which matched well with the changing of light (Pt atom) and darkness (Sn atom) (Figure 10b, e, h). Compared with cubic Pt3Sn nanocrystals, concave cubic Pt3Sn nanocrystals exhibited much deeper depressions and interfacial angles, and the ratio of concave surface area/entire surface area is much higher. Different from concave cubic Pt3Sn nanocrystals, defect-rich Pt3Sn nanocrystals have more depression on one face and larger angles (Figure 10 c,f,i). The defect-rich cubic intermetallic Pt3Sn nanocrystals exhibited superior and stable FOR properties, which can be ascribed to the structure stability of intermetallic compounds and defects riched surface (Figure 10 j,k). This encouraged us to design a variety of intermetallic nanocrystals with extraordinary surface structures.
26 ACS Paragon Plus Environment
Page 26 of 41
Page 27 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Figure 11. (a) STEM image of Pt3Co nanowires. Inset is an enlarged STEM image. (b) STEMADF image and EDS elemental mappings of the Pt3Co nanowires. (c) The enlarged HAADFSTEM and FFT-filtered HAADF-STEM images with L12-ordered intermetallic structure. The scale bars in a, inset of a, b and c are 200, 20, 10 and 1 nm, respectively. (d) ORR polarization curves and (e) ORR-specific activities and mass activities of different catalysts. Adapted with permission from reference 176. Copyright 2016 Nature. Kang174 reported the synthesis of shape controlled cubic and spherical Pt3Zn nanocrystals via a simple hydrothermal method. The spherical nanocatalyst exhibited higher MOR performance than that on cubic particles. The Pt-Zn alloy phase can be transformed into the Pt3Zn intermetallic phase during annealing since the higher temperature was needed to incorporate Zn into Pt. The intermetallic Pt3Zn showed enhanced performance relative to the alloy phase. To further, taking the advantage of concave cubic intermetallic Pt3Zn with facets, Chen, Q175 prepared Pt3Zn intermetallic compound nanocrystals by reduction of noble metal precursors through an under-potential deposition (UPD) process. As expected, it was demonstrated superior CO-tolerance capability and MOR and FOR electrocatalytic activity. The UPD of metal ions on a foreign metal substrate has the potential for the synthesis of other intermetallic compound. Recently, Bu and co-workers176 proposed the wet-chemical approach for the synthesis of the hierarchical Pt-Co nanowires with high-density high-index facts. The morphology consisted of 27 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
abundant crenel-like hierarchical 1D nanowires nanostructure (Figure 11a). The STEM-EDS were conducted to analyze the distributions of Pt and Co from the atomic level. The Pt and Co atoms were uniformly distributed through the whole alloying structure nanowire, which had all columns with equal intensity and without the super periodicity (Figure 11b). As contrast, the L12ordered Pt3Co intermetallic structure had a periodic square array of pure Co columns surrounded by Pt columns since the Pt columns had higher brightness than that of the Co columns (Figure 11c). Having high-index [310] and [110] crystal facets and Pt-rich surface, the ordered Pt-Co nanowires exhibited 39.6/33.7 times higher specific/mass activities for ORR relative to commercial Pt/C catalyst, respectively (Figure 11d, e). DFT further revealed that the platinumrich high-index facets were conductive to enhance active hollow sites and then improved the ORR activity and stability.
Figure 12. (a) TEM micrograph of 27 nm long and 9 nm wide Pd2Sn nanorods. (b) HRTEM micrographs, power spectra, and 3D atomic models of vertically and horizontally aligned Pd2Sn NRs. Adapted with permission from reference 177. Copyright 2015 American Chemical Society. (c) SEM images of Pd-Sn-INNs. Adapted with permission from reference 178. Copyright 2014 Elsevier. (d) TEM images of the synthesized PtBi intermetallic nanoplates. Adapted with permission from reference 179. Copyright 2014 Royal Society of Chemistry. For the intermetallic catalyst to form a nanorods structure, the difference in coordination numbers of the platinum or lead ad-atoms of the growing low-index surfaces should be 28 ACS Paragon Plus Environment
Page 28 of 41
Page 29 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
controlled. Maksimuk and co-workers180 prepared composition and shape controlled ordered intermetallic PtPb nanorods via an aqueous method with Pt(acac)2 and Pb(acac)2 as the metal source, dissolved in diphenyl ether, adamantanecarboxylic acid, hexadecanethiol and hexadecylamine solution. In a later report, monodisperse Pd2Sn nanorods with tunable size and ratio were synthesized via co-reduction of metal salts in the presence of trioctylphosphine, amine, and chloride ions (Figure 12a).177 The chlorine ions were used to remove surfactant and asymmetric Pd2Sn nanostructures were then obtained and displayed orthorhombic crystal structure (Figure 12b). In another example,178 the three-dimensional (3D) porous network nanostructures Pd-Sn intermetallics (Pd-Sn-INNs) were synthesized by one-step ethylene glycolassisted hydrothermal reduction strategy (Figure 12c). Having rich-morphology, the 3D Pd-SnINNs showed significantly enhanced electrocatalytic FOR activity and stability. Moreover, the intermetallic nanoparticles with lamellar179 (Figure 12d) and nanodendrites morphology181 are also reported. By adjusting the temperature, Wang182 prepared shape-controlled Pt3Sn, PtSn and PtSn2 intermetallic nanocatalysts via a versatile hot-injection strategy. They considered that temperature and metal composition had a crucial influence to the formation of morphologycontrolled intermetallic compound. Thus, the morphology-controlled methods can be served as a guide so as to acquire better performing electrocatalysts capable of meeting the goals of high activity, longer stability and low cost. It is essential to explore other methods for the formation of different morphologies to increase the activity of the catalyst.
4. Conclusion and Outlook In this review, recent progress on the intermetallic electrocatalysts for applications in fuel cells was introduced. Intermetallic compounds provide more precise control over the local geometry and electronic structure of the constituent metal atoms than their disorder alloy counterpart. Control of the composition, structure and morphology can, among other effects, cause the shift of d-band center and the adsorption energies of intermediates, and ultimately enhance catalytic performance. Not only does the catalytic activity increase, but also the poisoning effect is largely mitigated. Pt-based intermetallic compound with excellent performance are synthesized by rationally manipulating the surface chemical-adsorption properties via two types of methods: controlling particle size and morphology. The fundamental mechanistic for how the intermetallic 29 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
phases affect the catalytic performance could be categorized into four types of effects: ordering effects, strain or electronic effects, surface defects and crystal orientation (high exponential crystal surface). (1) Ordering effects: the structure transformation from the disordered to ordered structures upon annealing at high temperatures is spontaneous (ΔG0 < 0) and the change in entropy for ordering is negative (ΔS0 < 0), then theΔH0 must be shifted negatively (ΔH0 < 0). Hence, from a thermodynamic perspective, the ordered intermetallics may be more stable than the disordered alloys. (2) Strain effects or electronic effects: for both ordered intermetallics and disordered alloys, the addition of another metal (M) to Pt could change the Pt 5d band vacancy, Pt-Pt interatomic distance and change the electronic structures and strain of surface Pt, which can affect the stability of reaction intermediates and the activation energy of a chemical reaction and then affect higher chemical/structural stability and activity. Compared with disordered alloys, the ordered intermetallics have stronger interaction between Pt and M atoms and then exhibit stronger electronic or strain effects, which may be conductive to the enhancement of catalytic performance. (3) Surface defects and crystal orientation (high exponential crystal surface): for both ordered intermetallics and disordered alloys, the appearance of surface defects and high exponential crystal surface can enhance the intrinsic activity of the catalyst. However, the surface defects and high exponential crystal surface make the nanoparticles less stable. Incorporation the stable nature of ordered intermetallic with highly active surface defects and high exponential crystal surface not only can enhance the intrinsic activity of the catalyst owing to the stronger electronic or strain effects but also can enhance the durability of the catalyst. As mentioned in the review, tremendous progress has been acquired for the synthesis of Pt-based intermetallic compound catalysts. However, how to precisely control the sizes and shapes, bridge the gap between the laboratory studies and industrial scale-up is still a serious challenge. Moreover, the stability of these Pt (Pd)-based intermetallic compound catalysts is still limited to the leaching of non-precious metal and the aggregation of the particles. The current obtained catalysts have achieved excellent stability compared with commercial Pt/C, it is still far from enough for practical purposes. The possible strategies to cope with these challenges are proposed. Firstly, improve the ordered degree of intermetallics. Precisely control the annealing temperature and time can conductive to the structure transformation from partially ordered to fully ordered intermetallics, which is essential to enhance the catalytic activity and durability. Secondly, increase the proportion and intrinsic activity of active sites. Closely regulation the reaction 30 ACS Paragon Plus Environment
Page 30 of 41
Page 31 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
parameters, nanoparticle composition, microstructure and particle size, which can, in turn, increase the density and intrinsic activity of active sites and, consequently, enhance the catalytic activity. Furthermore, by increasing the interaction between the carrier/coating layer and the ordered intermetallic can improve the catalytic durability. Finally, forming core-shell structure with ordered intermetallic PtM core and Pt shell can enhance the catalytic activity as well as prevent the dissolving of transition metals and then enhance the durability of catalyst. Hence, the improvement in the rational design of various Pt (Pd)-based intermetallic compound catalysts by the control of size and morphology will have important implications. Determinately, the intermetallic compound will continue to play an important role as a choice for the most active and stable catalysts under acidic conditions. From an engineering perspective, intermetallic compound with controllable structure and particle size may achieve an optimized balance between the catalytic costs and the electrocatalytic performance.
AUTHOR INFORMATION Corresponding Author Prof. D.L. Wang Email:
[email protected] Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. W. Xiao and W. Lei contributed equally.
ACKNOWLEDGEMENT This work was supported by the National Natural Science Foundation (21573083), 1000 Young Talent (to Deli Wang). H. L. X. is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-SC0012704.
REFERENCES (1) Bing, Y.; Liu, H.; Zhang, L.; Ghosh, D.; Zhang, J. Nanostructured Pt-alloy electrocatalysts for PEM fuel cell oxygen reduction reaction. Chem. Soc. Rev. 2010, 39, 2184-2202. (2) Wang, Y. J.; Zhao, N.; Fang, B.; Li, H.; Bi, X. T.; Wang, H. Carbon-supported Pt-based alloy electrocatalysts for the oxygen reduction reaction in polymer electrolyte membrane fuel cells: particle size, shape, and composition manipulation and their impact to activity. Chem. Rev. 2015, 115, 3433-3467. (3) Lin, X.; Gao, G.; Zheng, L.; Chi, Y.; Chen, G. Encapsulation of strongly fluorescent carbon quantum dots in metal-organic frameworks for enhancing chemical sensing. Anal. Chem. 2013, 86, 1223-1228.
31 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
(4) Son, J.; Cho, S.; Lee, C.; Lee, Y.; Shim, J. H. Spongelike nanoporous Pd and Pd/Au structures: facile synthesis and enhanced electrocatalytic activity. Langmuir 2014, 30, 3579-3588. (5) Lim, B.; Jiang, M.; Camargo, P. H.; Cho, E. C.; Tao, J.; Lu, X.; Zhu, Y.; Xia, Y. Pd-Pt bimetallic nanodendrites with high activity for oxygen reduction. Science 2009, 324, 1302-1305. (6) Xiong, L.; Manthiram, A. Influence of atomic ordering on the electrocatalytic activity of Pt-Co alloys in alkaline electrolyte and proton exchange membrane fuel cells. J. Mater. Chem. 2004, 14, 1454-1460. (7) Nie, Y.; Li, L.; Wei, Z. Recent advancements in Pt and Pt-free catalysts for oxygen reduction reaction. Chem. Soc. Rev. 2015, 44, 2168-2201. (8) Xiao, B. B.; Zhu, Y. F.; Lang, X. Y.; Wen, Z.; Jiang, Q. Al13@Pt42 core-shell cluster for oxygen reduction reaction. Sci. Rep. 2014, 4, 5205. (9) Kuttiyiel, K. A.; Sasaki, K.; Choi, Y.; Su, D.; Liu, P.; Adzic, R. R. Nitride stabilized PtNi core-shell nanocatalyst for high oxygen reduction activity. Nano Lett. 2012, 12, 6266-6271. (10) Hu, G.; Nitze, F.; Gracia-Espino, E.; Ma, J.; Barzegar, H. R.; Sharifi, T.; Jia, X.; Shchukarev, A.; Lu, L.; Ma, C.; Yang, G.; Wagberg, T. Small palladium islands embedded in palladium-tungsten bimetallic nanoparticles form catalytic hotspots for oxygen reduction. Nat. Commun. 2014, 5, 5253. (11) Lin, R.; Zhao, T.; Shang, M.; Wang, J.; Tang, W.; Guterman, V. E.; Ma, J. Effect of heat treatment on the activity and stability of PtCo/C catalyst and application of in-situ X-ray absorption near edge structure for proton exchange membrane fuel cell. J. Power Sources 2015, 293, 274-282. (12) Praetorius, C.; Zinner, M.; Köhl, A.; Kießling, H.; Brück, S.; Muenzing, B.; Kamp, M.; Kachel, T.; Choueikani, F.; Ohresser, P. Electronic tuneability of a structurally rigid surface intermetallic and Kondo lattice: CePt5/Pt (111). Phys. Rev. B 2015, 92, 045116. (13) Liu, Y.; Abe, H.; Edvenson, H. M.; Ghosh, T.; Disalvo, F. J.; Abruna, H. D. Fabrication and surface characterization of single crystal PtBi and PtPb (100) and (001) surfaces. Phys. Chem. Chem. Phys. : PCCP 2010, 12, 12978-12986. (14) Stamenkovic, V. R.; Mun, B. S.; Arenz, M.; Mayrhofer, K. J.; Lucas, C. A.; Wang, G.; Ross, P. N.; Markovic, N. M. Trends in electrocatalysis on extended and nanoscale Pt-bimetallic alloy surfaces. Nat. Mater. 2007, 6, 241-247. (15) Cui, C.; Gan, L.; Heggen, M.; Rudi, S.; Strasser, P. Compositional segregation in shaped Pt alloy nanoparticles and their structural behaviour during electrocatalysis. Nat. Mater. 2013, 12, 765-771. (16) Cui, C.; Gan, L.; Li, H. H.; Yu, S. H.; Heggen, M.; Strasser, P. Octahedral PtNi nanoparticle catalysts: exceptional oxygen reduction activity by tuning the alloy particle surface composition. Nano Lett. 2012, 12, 58855889. (17) Lux, K. W.; Cairns, E. J. Lanthanide-Platinum Intermetallic Compounds as Anode Electrocatalysts for Direct Ethanol PEM Fuel Cells. J. Electrochem. Soc. 2006, 153, A1132-A1138. (18) Loukrakpam, R.; Shan, S.; Petkov, V.; Yang, L.; Luo, J.; Zhong, C.-J. Atomic Ordering Enhanced Electrocatalytic Activity of Nanoalloys for Oxygen Reduction Reaction. J. Phys. Chem. C 2013, 117, 20715-20721. (19) Chen, S.; Ferreira, P. J.; Sheng, W.; Yabuuchi, N.; Allard, L. F.; Shao-Horn, Y. Enhanced activity for oxygen reduction reaction on “Pt3Co” nanoparticles: direct evidence of percolated and sandwich-segregation structures. J. Am. Chem. Soc. 2008, 130, 13818-13819. (20) Schulenburg, H.; Muller, E.; Khelashvili, G.; Roser, T.; Bonnemann, H.; Wokaun, A.; Scherer, G. Heattreated PtCo3 nanoparticles as oxygen reduction catalysts. J. Phys. Chem. C 2009, 113, 4069-4077. (21) Ge, X.; Sumboja, A.; Wuu, D.; An, T.; Li, B.; Goh, F. W. T.; Hor, T. S. A.; Zong, Y.; Liu, Z. Oxygen Reduction in Alkaline Media: From Mechanisms to Recent Advances of Catalysts. ACS Catal. 2015, 4643-4667. (22) Li, X.; An, L.; Chen, X.; Zhang, N.; Xia, D.; Huang, W.; Chu, W.; Wu, Z. Durability enhancement of intermetallics electrocatalysts via N-anchor effect for fuel cells. Sci. Rep. 2013, 3, 3234. (23) Zou, L.; Fan, J.; Zhou, Y.; Wang, C.; Li, J.; Zou, Z.; Yang, H. Conversion of PtNi alloy from disordered to ordered for enhanced activity and durability in methanol-tolerant oxygen reduction reactions. Nano Res. 2015, 8, 2777-2788. (24) Elkins, K.; Li, D.; Poudyal, N.; Nandwana, V.; Jin, Z.; Chen, K.; Liu, J. P. Monodisperse face-centred tetragonal FePt nanoparticles with giant coercivity. J Phy D: Appl Phys. 2005, 38, 2306-2309. (25) Armbruster, M.; Wowsnick, G.; Friedrich, M.; Heggen, M.; Cardoso-Gil, R. Synthesis and catalytic properties of nanoparticulate intermetallic Ga-Pd compounds. J. Am. Chem. Soc. 2011, 133, 9112-9118. (26) Dai, Z.; Sun, S.; Wang, Z. Phase transformation, coalescence, and twinning of monodisperse FePt nanocrystals. Nano Lett. 2001, 1, 443-447.
32 ACS Paragon Plus Environment
Page 32 of 41
Page 33 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
(27) Chen, L.; Bock, C.; Mercier, P. H. J.; MacDougall, B. R. Ordered alloy formation for Pt3Fe/C, PtFe/C and Pt5.75Fe5.75Cuy/CO2-reduction electro-catalysts. Electrochim. Acta 2012, 77, 212-224. (28) Pan, Y. T.; Yan, Y.; Shao, Y. T.; Zuo, J. M.; Yang, H. Ag-Pt Compositional Intermetallics Made from Alloy Nanoparticles. Nano Lett. 2016, 16, 6599-6630. (29) Iihama, S.; Furukawa, S.; Komatsu, T. Efficient Catalytic System for Chemoselective Hydrogenation of Halonitrobenzene to Haloaniline Using PtZn Intermetallic Compound. ACS Catal. 2016, 6, 742-726. (30) Najafishirtari, S.; Brescia, R.; Guardia, P.; Marras, S.; Manna, L.; Colombo, M. Nanoscale Transformations of Alumina-Supported AuCu Ordered Phase Nanocrystals and Their Activity in CO Oxidation. ACS Catal. 2015, 5, 2154-2163. (31) Götsch, T.; Stöger-Pollach, M.; Thalinger, R.; Penner, S. The Nanoscale Kirkendall Effect in Pd-Based Intermetallic Phases. J. Phys. Chem. C 2014, 118, 17810-17818. (32) Sun, S.; Murray, C. B.; Weller, D.; Folks, L.; Moser, A. Monodisperse FePt nanoparticles and ferromagnetic FePt nanocrystal superlattices. Science 2000, 287, 1989-1992. (33) Alloyeau, D.; Ricolleau, C.; Mottet, C.; Oikawa, T.; Langlois, C.; Le Bouar, Y.; Braidy, N.; Loiseau, A. Size and shape effects on the order-disorder phase transition in CoPt nanoparticles. Nat. Mater. 2009, 8, 940-946. (34) Shibata, H.; Hayashi, H.; Akabori, M.; Arai, Y.; Kurata, M. Evaluation of Gibbs free energies of formation of Ce–Cd intermetallic compounds using electrochemical techniques. J. Phys. Chem. Solids 2014, 75, 972-976. (35) Kim, J.; Lee, Y.; Sun, S. Structurally ordered FePt nanoparticles and their enhanced catalysis for oxygen reduction reaction. J. Am. Chem. Soc. 2010, 132, 4996-4997. (36) Zou, L.; Li, J.; Yuan, T.; Zhou, Y.; Li, X.; Yang, H. Structural transformation of carbon-supported Pt3Cr nanoparticles from a disordered to an ordered phase as a durable oxygen reduction electrocatalyst. Nanoscale 2014, 6, 10686-10692. (37) Ota, A.; Armbrüster, M.; Behrens, M.; Rosenthal, D.; Friedrich, M.; Kasatkin, I.; Girgsdies, F.; Zhang, W.; Wagner, R.; Schlögl, R. Intermetallic compound Pd2Ga as a selective catalyst for the semi-hydrogenation of acetylene: from model to high performance systems. J. Phys. Chem. C 2010, 115, 1368-1374. (38) Krajčí, M.; Hafner, J. Intermetallic Compound AlPd As a Selective Hydrogenation Catalyst: A DFT Study. J. Phys. Chem. C 2012, 116, 6307-6319. (39) Chandrasekhar, N.; Sholl, D. S. J. Quantitative computational screening of Pd-based intermetallic membranes for hydrogen separation. Membrane Sci. 2014, 453, 516-524. (40) Osswald, J.; Kovnir, K.; Armbruster, M.; Giedigkeit, R.; Jentoft, R.; Wild, U.; Grin, Y.; Schlogl, R. Palladium-gallium intermetallic compounds for the selective hydrogenation of acetylenePart II: Surface characterization and catalytic performance. J. Catal. 2008, 258, 219-227. (41) Rudashevsky, N. S.; Rudashevsky, V. N.; Nielsen, T. F. D. Intermetallic compounds, copper and palladium alloys in Au-Pd ore of the Skaergaard pluton, Greenland. Geol.Ore Deposits 2016, 57, 674-690. (42) Armbruster, M.; Schlogl, R.; Grin, Y. Intermetallic compounds in heterogeneous catalysis-a quickly developing field. Sci. Technol. Adv. Mater. 2014, 15, 034803. (43) Antolini, E. Palladium in fuel cell catalysis. Energy & Environ. Sci. 2009, 2, 915-931. (44) Choi, R.; Jung, J.; Kim, G.; Song, K.; Kim, Y.-I.; Jung, S. C.; Han, Y.-K.; Song, H.; Kang, Y.-M. Ultra-low overpotential and high rate capability in Li-O2 batteries through surface atom arrangement of PdCu nanocatalysts. Energy & Environ. Sci. 2014, 7, 1362-1368. (45) Cui, Z.; Li, L.; Manthiram, A.; Goodenough, J. B. Enhanced Cycling Stability of Hybrid Li-Air Batteries Enabled by Ordered Pd3Fe Intermetallic Electrocatalyst. J. Am. Chem. Soc. 2015, 137, 7278-7281. (46) Arumugam, B.; Kakade, B. A.; Tamaki, T.; Arao, M.; Imai, H.; Yamaguchi, T. Enhanced activity and durability for the electroreduction of oxygen at a chemically ordered intermetallic PtFeCo catalyst. RSC Adv. 2014, 4, 27510-27517. (47) Cui, Z.; Chen, H.; Zhao, M.; DiSalvo, F. J. High-Performance PdPb Intermetallic Catalyst for Electrochemical Oxygen Reduction. Nano Lett. 2016, 4, 2560-2566. (48) Jiang, K.; Wang, P.; Guo, S.; Zhang, X.; Shen, X.; Lu, G.; Su, D.; Huang, X. Ordered PdCu-Based Nanoparticles as Bifunctional Oxygen-Reduction and Ethanol-Oxidation Electrocatalysts. Angew. Chem. Int. Ed. 2016, 55, 9030-9035. (49) Park, J.; Zhang, L.; Choi, S.-I.; Roling, L. T.; Lu, N.; Herron, J. A.; Xie, S.; Wang, J.; Kim, M. J.; Mavrikakis, M. Atomic Layer-by-Layer Deposition of Platinum on Palladium Octahedra for Enhanced Catalysts toward the Oxygen Reduction Reaction. ACS Nano 2015, 9, 2635-2647. (50) Cui, Z.; Chen, H.; Zhou, W.; Zhao, M.; DiSalvo, F. J. Structurally Ordered Pt3Cr as Oxygen Reduction Electrocatalyst: Ordering Control and Origin of Enhanced Stability. Chem. Mater. 2015, 27, 7538-7545.
33 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
(51) Prabhudev, S.; Bugnet, M.; Bock, C.; Botton, G. A. Strained Lattice with Persistent Atomic Order in Pt3Fe2 Intermetallic Core-Shell Nanocatalysts. ACS Nano 2013, 7, 6103-6110. (52) Bu, L.; Zhang, N.; Guo, S.; Zhang, X.; Li, J.; Yao, J.; Wu, T.; Lu, G.; Ma, J.-Y.; Su, D. Biaxially strained PtPb/Pt core/shell nanoplate boosts oxygen reduction catalysis. Science 2016, 354, 1410-1414. (53) Malacrida, P.; Escudero-Escribano, M.; Verdaguer-Casadevall, A.; Stephens, I. E. L.; Chorkendorff, I. Enhanced activity and stability of Pt-La and Pt-Ce alloys for oxygen electroreduction: the elucidation of the active surface phase. J. Mater. Chem. A 2014, 2, 4234-4243. (54) Li, X.; An, L.; Wang, X.; Li, F.; Zou, R.; Xia, D. Supported sub-5nm Pt-Fe intermetallic compounds for electrocatalytic application. J. Mater. Chem. 2012, 22, 6047-6052. (55) Zhang, S.; Qi, W.; Huang, B. Size effect on order-disorder transition kinetics of FePt nanoparticles. J. Chem. Phys. 2014, 140, 044328. (56) Arán-Ais, R. M.; Solla-Gullón, J.; Gocyla, M.; Heggen, M.; Dunin-Borkowski, R. E.; Strasser, P.; Herrero, E.; Feliu, J. M. The effect of interfacial pH on the surface atomic elemental distribution and on the catalytic reactivity of shape-selected bimetallic nanoparticles towards oxygen reduction. Nano Energy 2016, 27, 390-401. (57) Xia, B. Y.; Wu, H. B.; Wang, X.; Lou, X. W. One-pot synthesis of cubic PtCu3 nanocages with enhanced electrocatalytic activity for the methanol oxidation reaction. J. Am. Chem. Soc. 2012, 134, 13934-13937. (58) Casado-Rivera, E.; Volpe, D. J.; Alden, L.; Lind, C.; Downie, C.; Vázquez-Alvarez, T.; Angelo, A. C.; DiSalvo, F. J.; Abruna, H. D. Electrocatalytic activity of ordered intermetallic phases for fuel cell applications. J. Am. Chem. Soc. 2004, 126, 4043-4049. (59) Meku, E.; Du, C.; Sun, Y.; Du, L.; Wang, Y.; Yin, G. Electrocatalytic Activity and Stability of Ordered Intermetallic Palladium-Iron Nanoparticles toward Oxygen Reduction Reaction. J. Electrochem. Soc. 2015, 163, F132-F138. (60) Kodiyath, R.; Ramesh, G. V.; Koudelkova, E.; Tanabe, T.; Ito, M.; Manikandan, M.; Ueda, S.; Fujita, T.; Umezawa, N.; Noguchi, H. Promoted C-C bond cleavage over intermetallic TaPt3 catalyst toward low-temperature energy extraction from ethanol. Energy & Environ. Sci. 2015, 6, 1685-1689. (61) Xie, X.; Gao, G.; Pan, Z.; Wang, T.; Meng, X.; Cai, L. Large-scale synthesis of palladium concave nanocubes with high-index facets for sustainable enhanced catalytic performance. Sci. Rep. 2015, 5, 8515. (62) Gunji, T.; Tanabe, T.; Jeevagan, A. J.; Usui, S.; Tsuda, T.; Kaneko, S.; Saravanan, G.; Abe, H.; Matsumoto, F. Facile route for the preparation of ordered intermetallic Pt3Pb-PtPb core-shell nanoparticles and its enhanced activity for alkaline methanol and ethanol oxidation. J. Power Sources 2015, 273, 990-998. (63) Zhu, J.; Zheng, X.; Wang, J.; Wu, Z.; Han, L.; Lin, R.; Xin, H. L.; Wang, D. Facile route for the preparation of ordered intermetallic Pt3Pb-PtPb core-shell nanoparticles and its enhanced activity for alkaline methanol and ethanol oxidation. J. Mater. Chem. A 2015, 3, 22129-22135. (64) Yamamoto, S.; Morimoto, Y.; Tamada, Y.; Takahashi, Y.; Hono, K.; Ono, T.; Takano, M. Preparation of Monodisperse and Highly Coercive L10-FePt Nanoparticles Dispersible in Nonpolar Organic Solvents. Chem. Mater. 2006, 18, 5385-5388. (65) Tamada, Y.; Yamamoto, S.; Takano, M.; Nasu, S.; Ono, T. Well-ordered L1[sub 0]-FePt nanoparticles synthesized by improved SiO[sub 2]-nanoreactor method. Appl. Phys. Lett. 2007, 90, 162509. (66) Shan, S.; Petkov, V.; Prasai, B.; Wu, J.; Joseph, P.; Skeete, Z.; Kim, E.; Mott, D.; Malis, O.; Luo, J.; Zhong, C. J. Catalytic activity of bimetallic catalysts highly sensitive to the atomic composition and phase structure at the nanoscale. Nanoscale 2015, 7, 18936-18948. (67) Yu, Y.; Yang, W.; Sun, X.; Zhu, W.; Li, X. Z.; Sellmyer, D. J.; Sun, S. Monodisperse MPt (M = Fe, Co, Ni, Cu, Zn) nanoparticles prepared from a facile oleylamine reduction of metal salts. Nano Lett. 2014, 14, 2778-2782. (68) Tamaki, T.; Minagawa, A.; Arumugam, B.; Kakade, B. A.; Yamaguchi, T. J. Power Sources 2014, 271, 346-353. (69) Lu, X.; Tuan, H.-Y.; Chen, J.; Li, Z.-Y.; Korgel, B. A.; Xia, Y. Highly active and durable chemically ordered Pt-Fe-Co intermetallics as cathode catalysts of membrane-electrode assemblies in polymer electrolyte fuel cells. J. Am. Chem. Soc. 2007, 129, 1733-1742. (70) DeSario, D. Y.; DiSalvo, F. J. Ordered Intermetallic Pt–Sn Nanoparticles: Exploring Ordering Behavior across the Bulk Phase Diagram. Chem. Mater. 2014, 26, 2750-2757. (71) Cui, Z.; Liu, C.; Liao, J.; Xing, W. Highly active PtRu catalysts supported on carbon nanotubes prepared by modified impregnation method for methanol electro-oxidation. Electrochim. Acta 2008, 53, 7807-7811. (72) Gunji, T.; Sakai, K.; Suzuki, Y.; Kaneko, S.; Tanabe, T.; Matsumoto, F. Enhanced oxygen reduction reaction on PtPb ordered intermetallic nanoparticle/TiO2/carbon black in acidic aqueous solutions. Catal. Commun. 2015, 61, 1-5.
34 ACS Paragon Plus Environment
Page 34 of 41
Page 35 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
(73) Kim, J.; Yang, S.; Lee, H. Platinum-titanium intermetallic nanoparticle catalysts for oxygen reduction reaction with enhanced activity and durability. Electrochem. Commun. 2016, 66, 66-70. (74) Furukawa, S.; Yokoyama, A.; Komatsu, T. Efficient Catalytic System for Synthesis oftrans-Stilbene from Diphenylacetylene Using Rh-Based Intermetallic Compounds. ACS Catal. 2014, 4, 3581-3585. (75) Guo, S.; Sun, S. FePt nanoparticles assembled on graphene as enhanced catalyst for oxygen reduction reaction. J. Am. Chem. Soc. 2012, 134, 2492-2495. (76) Zhang, B.-W.; Jiang, Y.-X.; Ren, J.; Qu, X.-M.; Xu, G.-L.; Sun, S.-G. PtBi intermetallic and PtBi intermetallic with the Bi-rich surface supported on porous graphitic carbon towards HCOOH electro-oxidation. Electrochim. Acta 2015, 162, 254-262. (77) Yu, J.-S.; Kang, S.; Yoon, S. B.; Chai, G. Fabrication of ordered uniform porous carbon networks and their application to a catalyst supporter. J. Am. Chem. Soc. 2002, 124, 9382-9383. (78) Joo, S. H.; Choi, S. J.; Oh, I.; Kwak, J.; Liu, Z.; Terasaki, O.; Ryoo, R. Ordered nanoporous arrays of carbon supporting high dispersions of platinum nanoparticles. Nature 2001, 412, 169-172. (79) Ji, X.; Lee, K. T.; Holden, R.; Zhang, L.; Zhang, J.; Botton, G. A.; Couillard, M.; Nazar, L. F. Nanocrystalline intermetallics on mesoporous carbon for direct formic acid fuel cell anodes. Nat. Chem. 2010, 2, 286-293. (80) Lee, J.; Kim, J.; Hyeon, T. Recent Progress in the Synthesis of Porous Carbon Materials. Adv. Mater. 2006, 18, 2073-2094. (81) Liu, R.; Shi, Y.; Wan, Y.; Meng, Y.; Zhang, F.; Gu, D.; Chen, Z.; Tu, B.; Zhao, D. Triconstituent Coassembly to Ordered Mesostructured Polymer-Silica and Carbon-Silica Nanocomposites and Large-Pore Mesoporous Carbons with High Surface Areas. J. Am. Chem. Soc. 2006, 128, 11652-11662. (82) Shim, J.; Lee, J.; Ye, Y.; Hwang, J.; Kim, S.-K.; Lim, T.-H.; Wiesner, U.; Lee, J. One-Pot Synthesis of Intermetallic Electrocatalysts in Ordered, Large-Pore Mesoporous Carbon/Silica toward Formic Acid Oxidation. ACS Nano 2012, 6, 6870-6881. (83) Zhang, B.-W.; He, C.-L.; Jiang, Y.-X.; Chen, M.-H.; Li, Y.-Y.; Rao, L.; Sun, S.-G. High activity of PtBi intermetallics supported on mesoporous carbon towards HCOOH electro-oxidation. Electrochem. Commun. 2012, 25, 105-108. (84) Wu, J.; Pisula, W.; Müllen, K. Graphenes as potential material for electronics. Chem. Rev. 2007, 107, 718747. (85) Kumar, V. B.; Sanetuntikul, J.; Ganesan, P.; Porat, Z. e.; Shanmugam, S.; Gedanken, A. Sonochemical Formation of Ga-Pt Intermetallic Nanoparticles Embedded in Graphene and its Potential Use as an Electrocatalyst. Electrochim. Acta 2016, 190, 659-667. (86) Gunji, T.; Jeevagan, A. J.; Hashimoto, M.; Nozawa, T.; Tanabe, T.; Kaneko, S.; Miyauchi, M.; Matsumoto, F. Photocatalytic decomposition of various organic compounds over WO3-supported ordered intermetallic PtPb cocatalysts. Appl. Catal. B: Environ. 2016, 181, 475-480. (87) Komatsu, T.; Tamura, A. Pt3Co and PtCu intermetallic compounds: Promising catalysts for preferential oxidation of CO in excess hydrogen. J. Catal. 2008, 258, 306-314. (88) Komatsu, T.; Sou, K.; Ozawa, K.-i. Preparation and catalytic properties of fine particles of Pt-Ge intermetallic compound formed inside the mesopores of MCM-41. J. Mol. Catal. A: Chem. 2010, 319, 71-77. (89) Lee, D. C.; Mikulec, F. V.; Pelaez, J. M.; Koo, B.; Korgel, B. A. Synthesis and magnetic properties of silica-coated FePt nanocrystals. J. Phys. Chem. B 2006, 110, 11160-11166. (90) Kim, J.; Rong, C.; Lee, Y.; Liu, J. P.; Sun, S. From core/shell structured FePt/Fe3O4/MgO to ferromagnetic FePt nanoparticles. Chem. Mater. 2008, 20, 7242-7245. (91) Yabuhara, O.; Ohtake, M.; Tobari, K.; Nishiyama, T.; Kirino, F.; Futamoto, M. Structural and magnetic properties of FePd and CoPd alloy epitaxial thin films grown on MgO single-crystal substrates with different orientations. Thin Solid Films 2011, 519, 8359-8362. (92) Komatsu, T.; Takasaki, M.; Ozawa, K.; Furukawa, S.; Muramatsu, A. PtCu Intermetallic Compound Supported on Alumina Active for Preferential Oxidation of CO in Hydrogen. J. Phys. Chem. C 2013, 117, 1048310491. (93) Gallagher, J. R.; Childers, D. J.; Zhao, H.; Winans, R. E.; Meyer, R. J.; Miller, J. T. Structural evolution of an intermetallic Pd-Zn catalyst selective for propane dehydrogenation. Phys. Chem. Chem. Phys. : PCCP 2015, 17, 28144-28153. (94) Jeevagan, A. J.; Gunji, T.; Ando, F.; Tanabe, T.; Kaneko, S.; Matsumoto, F. Enhancement of the electrocatalytic oxygen reduction reaction on Pd3Pb ordered intermetallic catalyst in alkaline aqueous solutions. J. Appl. Electrochem. 2016, 46, 745-753.
35 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
(95) Small, M. W.; Sanchez, S. I.; Menard, L. D.; Kang, J. H.; Frenkel, A. I.; Nuzzo, R. G. The atomic structural dynamics of gamma-Al2O3 supported Ir-Pt nanocluster catalysts prepared from a bimetallic molecular precursor: a study using aberration-corrected electron microscopy and X-ray absorption spectroscopy. J. Am. Chem. Soc. 2011, 133, 3582-3591. (96) Li, Q.; Wu, L.; Wu, G.; Su, D.; Lv, H.; Zhang, S.; Zhu, W.; Casimir, A.; Zhu, H.; Mendoza-Garcia, A.; Sun, S. New approach to fully ordered fct-FePt nanoparticles for much enhanced electrocatalysis in acid. Nano Lett. 2015, 15, 2468-2473. (97) Takahashi, Y.; Kadono, T.; Yamamoto, S.; Singh, V.; Verma, V.; Ishigami, K.; Shibata, G.; Harano, T.; Takeda, Y.; Okane, T. Orbital magnetic moment and coercivity of Si O 2-coated FePt nanoparticles studied by x-ray magnetic circular dichroism. Phys. Rev. B 2014, 90, 024423. (98) Chung, D. Y.; Jun, S. W.; Yoon, G.; Kwon, S. G.; Shin, D. Y.; Seo, P.; Yoo, J. M.; Shin, H.; Chung, Y. H.; Kim, H.; Mun, B. S.; Lee, K. S.; Lee, N. S.; Yoo, S. J.; Lim, D. H.; Kang, K.; Sung, Y. E.; Hyeon, T. Highly Durable and Active PtFe Nanocatalyst for Electrochemical Oxygen Reduction Reaction. J. Am. Chem. Soc. 2015, 137, 15478-15485. (99) Arumugam, B.; Tamaki, T.; Yamaguchi, T. Beneficial role of copper in the enhancement of durability of ordered intermetallic PtFeCu catalyst for electrocatalytic oxygen reduction. ACS Appl. Mater. & Inter. 2015, 7, 16311-16321. (100) Qi, Z.; Xiao, C.; Liu, C.; Goh, T. W.; Zhou, L.; Maligal-Ganesh, R.; Pei, Y.; Li, X.; Curtiss, L. A.; Huang, W. Sub-4 nm PtZn Intermetallic Nanoparticles for Enhanced Mass and Specific Activities in Catalytic Electrooxidation Reaction. J. Am. Chem. Soc. 2017, 139, 4762-4768. (101) Jiang, G.; Zhu, H.; Zhang, X.; Shen, B.; Wu, L.; Zhang, S.; Lu, G.; Wu, Z.; Sun, S. Core/shell facecentered tetragonal FePd/Pd nanoparticles as an efficient non-Pt catalyst for the oxygen reduction reaction. ACS Nano 2015, 9, 11014-11022. (102) Maligal-Ganesh, R. V.; Xiao, C.; Goh, T. W.; Wang, L.-L.; Gustafson, J.; Pei, Y.; Qi, Z.; Johnson, D. D.; Zhang, S.; Tao, F.; Huang, W. A Ship-in-a-Bottle Strategy To Synthesize Encapsulated Intermetallic Nanoparticle Catalysts: Exemplified for Furfural Hydrogenation. ACS Catal. 2016, 6, 1754-1763. (103) Komatsu, T. Nano-size particles of palladium intermetallic compounds as catalysts for oxidative acetoxylation. Appl. Catal. A: Gen. 2003, 251, 315-326. (104) Yamamoto, S.; Morimoto, Y.; Ono, T.; Takano, M. Magnetically superior and easy to handle L10-FePt nanocrystals. Appl. Phys. Lett. 2005, 87, 032503. (105) Furukawa, S.; Endo, M.; Komatsu, T. Bifunctional Catalytic System Effective for Oxidative Dehydrogenation of 1-Butene andn-Butane Using Pd-Based Intermetallic Compounds. ACS Catal. 2014, 4, 35333542. (106) Furukawa, S.; Suga, A.; Komatsu, T. Mechanistic Study on Aerobic Oxidation of Amine over Intermetallic Pd3Pb: Concerted Promotion Effects by Pb and Support Basicity. ACS Catal. 2015, 5, 1214-1222. (107) Furukawa, S.; Yoshida, Y.; Komatsu, T. Chemoselective Hydrogenation of Nitrostyrene to Aminostyrene over Pd- and Rh-Based Intermetallic Compounds. ACS Catal. 2014, 4, 1441-1450. (108) Fiordaliso, E. M.; Sharafutdinov, I.; Carvalho, H. W. P.; Grunwaldt, J.-D.; Hansen, T. W.; Chorkendorff, I.; Wagner, J. B.; Damsgaard, C. D. Intermetallic GaPd2 Nanoparticles on SiO2 for Low-Pressure CO2 Hydrogenation to Methanol: Catalytic Performance and In Situ Characterization. ACS Catal. 2015, 5, 5827-5836. (109) Li, G.; Kobayashi, H.; Kusada, K.; Taylor, J. M.; Kubota, Y.; Kato, K.; Takata, M.; Yamamoto, T.; Matsumura, S.; Kitagawa, H. An ordered bcc CuPd nanoalloy synthesised via the thermal decomposition of Pd nanoparticles covered with a metal-organic framework under hydrogen gas. Chem Commun. (Camb) 2014, 50, 13750-13753. (110) Oyola-Rivera, O.; Baltanás, M. A.; Cardona-Martínez, N. CO2 hydrogenation to methanol and dimethyl ether by Pd-Pd2Ga catalysts supported over Ga2O3 polymorphs. J. CO2 Util. 2015, 9, 8-15. (111) Kovnir, K.; Armbrüster, M.; Teschner, D.; Venkov, T. V.; Szentmiklósi, L.; Jentoft, F. C.; Knop-Gericke, A.; Grin, Y.; Schlögl, R. In situ surface characterization of the intermetallic compound PdGa-A highly selective hydrogenation catalyst. Surf. Sci. 2009, 603, 1784-1792. (112) Yu, Y.; Sun, K.; Tian, Y.; Li, X. Z.; Kramer, M. J.; Sellmyer, D. J.; Shield, J. E.; Sun, S. One-pot synthesis of urchin-like FePd-Fe3O4 and their conversion into exchange-coupled L1(0)-FePd-Fe nanocomposite magnets. Nano Lett. 2013, 13, 4975-4979. (113) Yang, J.; Chen, X.; Yang, X.; Ying, J. Y. Stabilization and compressive strain effect of AuCu core on Pt shell for oxygen reduction reaction. Energy & Environ. Sci. 2012, 5, 8976-8981.
36 ACS Paragon Plus Environment
Page 36 of 41
Page 37 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
(114) Lee, Y.; Jang, J.; Lee, J. G.; Jeon, O. S.; Kim, H. S.; Hwang, H. J.; Shul, Y. G. Optimization of the Pd-FeMo Catalysts for Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells. Electrochim. Acta 2016, 220, 29-35. (115) Ford, I. Nucleation theorems, the statistical mechanics of molecular clusters, and a revision of classical nucleation theory. Phys. Rev. E 1997, 56, 5615. (116) Kalikmanov, V. Classical nucleation theory. In Nucleation theory; Springer: 2013, 17-41. (117) Gilroy, K. D.; Ruditskiy, A.; Peng, H. C.; Qin, D.; Xia, Y. Bimetallic Nanocrystals: Syntheses, Properties, and Applications. Chem. Rev. 2016, 116, 10414-10472. (118) Scachetti, T. P.; Angelo, A. C. D. Ordered Intermetallic Nanostructured PtSb/C for Production of Energy and Chemicals. Electrocatalysis 2015, 6, 472-480. (119) Tsunoyama, H.; Ichikuni, N.; Sakurai, H.; Tsukuda, T. Effect of electronic structures of Au clusters stabilized by poly (N-vinyl-2-pyrrolidone) on aerobic oxidation catalysis. J. Am. Chem. Soc. 2009, 131, 7086-7093. (120) Sra, A. K.; Schaak, R. E. Synthesis of Atomically Ordered AuCu and AuCu3 Nanocrystals from Bimetallic Nanoparticle Precursors. J. Am. Chem. Soc. 2004, 126, 6667-6672. (121) Xia, D.; Chen, G.; Wang, Z.; Zhang, J.; Hui, S.; Ghosh, D.; Wang, H. Synthesis of ordered intermetallic PtBi2 nanoparticles for methanol-tolerant catalyst in oxygen electroreduction. Chem. Mater. 2006, 18, 5746-5749. (122) Zhang, D.; Wu, F.; Peng, M.; Wang, X.; Xia, D.; Guo, G. One-Step, Facile and Ultrafast Synthesis of Phase- and Size-Controlled Pt-Bi Intermetallic Nanocatalysts through Continuous-Flow Microfluidics. J. Am. Chem. Soc. 2015, 137, 6263-6269. (123) Howard, L. E.; Nguyen, H. L.; Giblin, S. R.; Tanner, B. K.; Terry, I.; Hughes, A. K.; Evans, J. S. A synthetic route to size-controlled fcc and fct FePt nanoparticles. J. Am. Chem. Soc. 2005, 127, 10140-472. (124) Zhang, S.; Guo, S.; Zhu, H.; Su, D.; Sun, S. Structure-induced enhancement in electrooxidation of trimetallic FePtAu nanoparticles. J. Am. Chem. Soc. 2012, 134, 5060-5063. (125) Wang, C.; Chen, D. P.; Sang, X.; Unocic, R. R.; Skrabalak, S. E. Size-Dependent Disorder-Order Transformation in the Synthesis of Monodisperse Intermetallic PdCu Nanocatalysts. ACS Nano 2016, 10, 6345-6353. (126) Kariuki, N. N.; Wang, X.; Mawdsley, J. R.; Ferrandon, M. S.; Niyogi, S. G.; Vaughey, J. T.; Myers, D. J. Colloidal Synthesis and Characterization of Carbon-Supported Pd-Cu Nanoparticle Oxygen Reduction Electrocatalysts. Chem. Mater. 2010, 22, 4144-4152. (127) Sarkar, S.; Jana, R.; Suchitra; Waghmare, U. V.; Kuppan, B.; Sampath, S.; Peter, S. C. Ordered Pd2Ge Intermetallic Nanoparticles as Highly Efficient and Robust Catalyst for Ethanol Oxidation. Chem. Mater. 2015, 27, 7459-7467. (128) Chen, H.; Wang, D.; Yu, Y.; Newton, K. A.; Muller, D. A.; Abruna, H.; DiSalvo, F. J. A surfactant-free strategy for synthesizing and processing intermetallic platinum-based nanoparticle catalysts. J. Am. Chem. Soc. 2012, 134, 18453-18459. (129) Cui, Z.; Chen, H.; Zhao, M.; Marshall, D.; Yu, Y.; Abruna, H.; DiSalvo, F. J. Synthesis of structurally ordered Pt3Ti and Pt3V nanoparticles as methanol oxidation catalysts. J. Am. Chem. Soc. 2014, 136, 10206-10209. (130) Magno, L. M.; Angelescu, D. G.; Sigle, W.; Stubenrauch, C. Microemulsions as reaction media for the synthesis of Pt nanoparticles. Phys. Chem. Chem. Phys. : PCCP 2011, 13, 3048-3058. (131) Magno, L. M.; Sigle, W.; van Aken, P. A.; Angelescu, D.; Stubenrauch, C. Size control of PtPb intermetallic nanoparticles prepared via microemulsions. Phys. Chem. Chem. Phys. : PCCP 2011, 13, 9134-9136. (132) Nguyen, H. L.; Howard, L. E. M.; Giblin, S. R.; Tanner, B. K.; Terry, I.; Hughes, A. K.; Ross, I. M.; Serres, A.; Bürckstümmer, H.; Evans, J. S. O. Synthesis of monodispersed fcc and fct FePt/FePd nanoparticles by microwave irradiation. J. Mater. Chem. 2005, 15, 5136-5143. (133) Zhang, N.; Chen, X.; Lu, Y.; An, L.; Li, X.; Xia, D.; Zhang, Z.; Li, J. Nano‐Intermetallic AuCu3 Catalyst for Oxygen Reduction Reaction: Performance and Mechanism. Small, 2014, 10, 2662-2669. (134) Zhang, N.; Yan, H.; Chen, X.; An, L.; Xia, Z.; Xia, D. Origins for the Synergetic Effects of AuCu3 in Catalysis for Oxygen Reduction Reaction. J. Phys. Chem. C, 2015, 119, 907-912. (135) Mun, J. H.; Chang, Y. H.; Shin, D. O.; Yoon, J. M.; Choi, D. S.; Lee, K.-M.; Kim, J. Y.; Cha, S. K.; Lee, J. Y.; Jeong, J.-R. Monodisperse Pattern Nanoalloying for Synergistic Intermetallic Catalysis. Nano Lett. 2013, 13, 5720-5726. (136) Tokushige, M.; Nishikiori, T.; Lafouresse, M. C.; Michioka, C.; Yoshimura, K.; Fukunaka, Y.; Ito, Y. Formation of FePt intermetallic compound nanoparticles by plasma-induced cathodic discharge electrolysis. Electrochim. Acta 2010, 55, 8154-8159.
37 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
(137) Liu, K.; Liu, Y.-L.; Yuan, L.-Y.; Wang, L.; Wang, L.; Li, Z.-J.; Chai, Z.-F.; Shi, W.-Q. Thermodynamic and electrochemical properties of holmium and HoxAly intermetallic compounds in the LiCl-KCl eutectic. Electrochim. Acta 2015, 174, 15-25. (138) Chen, H.; Yu, Y.; Xin, H. L.; Newton, K. A.; Holtz, M. E.; Wang, D.; Muller, D. A.; Abruña, H. c. D.; DiSalvo, F. J. Coalescence in the Thermal Annealing of Nanoparticles: An in Situ STEM Study of the Growth Mechanisms of Ordered Pt-Fe Nanoparticles in a KCl Matrix. Chem. Mater. 2013, 25, 1436-1442. (139) Dong, A.; Chen, J.; Ye, X.; Kikkawa, J. M.; Murray, C. B. Enhanced thermal stability and magnetic properties in NaCl-type FePt-MnO binary nanocrystal superlattices. J. Am. Chem. Soc. 2011, 133, 13296. (140) Hou, Y.; Kondoh, H.; Kogure, T.; Ohta, T. Preparation and characterization of monodisperse FePd nanoparticles. Chem. Mater. 2004, 16, 5149-5152. (141) Shevchenko, E. V.; Talapin, D. V.; Rogach, A. L.; Kornowski, A.; Haase, M.; Weller, H. Colloidal synthesis and self-assembly of CoPt3 nanocrystals. J. Am. Chem. Soc. 2002, 124, 11480-11485. (142) Bele, M.; Jovanovič, P.; Pavlišič, A.; Jozinović, B.; Zorko, M.; Rečnik, A.; Chernyshova, E.; Hočevar, S.; Hodnik, N.; Gaberšček, M. A highly active PtCu3 intermetallic core-shell, multilayered Pt-skin, carbon embedded electrocatalyst produced by a scale-up sol-gel synthesis. Chem. Commun. 2014, 50, 13124-13126. (143) Park, J.-I.; Kim, M. G.; Jun, Y.-w.; Lee, J. S.; Lee, W.-r.; Cheon, J. Characterization of superparamagnetic “core-shell” nanoparticles and monitoring their anisotropic phase transition to ferromagnetic “solid solution” nanoalloys. J. Am. Chem. Soc. 2004, 126, 9072-9078. (144) Xie, S.; Choi, S.-I.; Lu, N.; Roling, L. T.; Herron, J. A.; Zhang, L.; Park, J.; Wang, J.; Kim, M. J.; Xie, Z. Atomic Layer-by-Layer Deposition of Pt on Pd Nanocubes for Catalysts with Enhanced Activity and Durability toward Oxygen Reduction. Nano Lett. 2014, 14, 3570-3576. (145) Liu, H.; Dou, M.; Wang, F.; Liu, J.; Ji, J.; Li, Z. Ordered intermetallic PtFe@Pt core-shell nanoparticles supported on carbon nanotubes with superior activity and durability as oxygen reduction reaction electrocatalysts. RSC Adv. 2015, 5, 66471-66475. (146) Zhao, X.; Chen, S.; Fang, Z.; Ding, J.; Sang, W.; Wang, Y.; Zhao, J.; Peng, Z.; Zeng, J. Octahedral
[email protected] core-shell nanocrystals with ultrathin PtNi alloy shells as active catalysts for oxygen reduction reaction. J. Am. Chem. Soc. 2015, 137, 2804-2807. (147) Cho, K. Y.; Yeom, Y. S.; Seo, H. Y.; Kumar, P.; Lee, A. S.; Baek, K. Y.; Yoon, H. G. Molybdenum-Doped PdPt@Pt Core-Shell Octahedra Supported by Ionic Block Copolymer-Functionalized Graphene as a Highly Active and Durable Oxygen Reduction Electrocatalyst. ACS Appl. Mater. & Inter. 2017, 9, 1524-1535. (148) Wang, G.; Huang, B.; Xiao, L.; Ren, Z.; Chen, H.; Wang, D.; Abruna, H. D.; Lu, J.; Zhuang, L. Pt skin on AuCu intermetallic substrate: a strategy to maximize Pt utilization for fuel cells. J. Am. Chem. Soc. 2014, 136, 96439649. (149) Wang, G.; Guan, J.; Xiao, L.; Huang, B.; Wu, N.; Lu, J.; Zhuang, L. Pd skin on AuCu intermetallic nanoparticles: A highly active electrocatalyst for oxygen reduction reaction in alkaline media. Nano Energy, 2016, 29, 268-274. (150) Ghosh, T.; Vukmirovic, M. B.; DiSalvo, F. J.; Adzic, R. R. Intermetallics as novel supports for Pt monolayer O2 reduction electrocatalysts: potential for significantly improving properties. J. Am. Chem. Soc. 2010, 132, 906-907. (151) Mayr, L.; Lorenz, H.; Armbrüster, M.; Villaseca, S. A.; Luo, Y.; Cardoso, R.; Burkhardt, U.; Zemlyanov, D.; Haevecker, M.; Blume, R.; Knop-Gericke, A.; Klötzer, B.; Penner, S. The catalytic properties of thin film Pdrich GaPd2 in methanol steam reforming. J. Catal. 2014, 309, 231-240. (152) Liu, Z.; Jackson, G. S.; Eichhorn, B. W. PtSn intermetallic, core-shell, and alloy nanoparticles as COtolerant electrocatalysts for H2 oxidation. Angew. Chem. Int. Ed. 2010, 49, 3173-3176. (153) Wang, D.; Xin, H. L.; Hovden, R.; Wang, H.; Yu, Y.; Muller, D. A.; DiSalvo, F. J.; Abruña, H. D. Structurally ordered intermetallic platinum-cobalt core-shell nanoparticles with enhanced activity and stability as oxygen reduction electrocatalysts. Nat. Mater. 2013, 12, 81-87. (154) Bu, L.; Shao, Q.; E, B.; Guo, J.; Yao, J.; Huang, X. PtPb/PtNi Intermetallic Core/Atomic Layer Shell Octahedra for Efficient Oxygen Reduction Electrocatalysis. J. Am. Chem. Soc. 2017, 28, 9576-9582. (155) Matsumoto, F.; Roychowdhury, C.; DiSalvo, F. J.; Abruña, H. D. Electrocatalytic activity of ordered intermetallic PtPb nanoparticles prepared by borohydride reduction toward formic acid oxidation. J. Electrochem. Soc. 2008, 155, B148-B154. (156) Kang, Y.; Qi, L.; Li, M.; Diaz, R. E.; Su, D.; Adzic, R. R.; Stach, E.; Li, J.; Murray, C. B. Highly Active Pt3Pb and Core-Shell Pt3Pb-Pt Electrocatalysts for Formic Acid Oxidation. ACS Nano 2012, 6, 2818-2825.
38 ACS Paragon Plus Environment
Page 38 of 41
Page 39 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
(157) An, L.; Yan, H.; Chen, X.; Li, B.; Xia, Z.; Xia, D. Catalytic performance and mechanism of N-CoTi@ CoTiO3 catalysts for oxygen reduction reaction. Nano Energy, 2016, 20, 134-143. (158) Zhu, C.; Du, D.; Eychmuller, A.; Lin, Y. Engineering Ordered and Nonordered Porous Noble Metal Nanostructures: Synthesis, Assembly, and Their Applications in Electrochemistry. Chem. Rev. 2015, 115, 88968943. (159) Liu, H. L.; Nosheen, F.; Wang, X. Noble metal alloy complex nanostructures: controllable synthesis and their electrochemical property. Chem. Soc. Rev. 2015, 44, 3056-3078. (160) Li, M.; Zhao, Z.; Cheng, T.; Fortunelli, A.; Chen, C. Y.; Yu, R.; Zhang, Q.; Gu, L.; Merinov, B. V.; Lin, Z.; Zhu, E.; Yu, T.; Jia, Q.; Guo, J.; Zhang, L.; Goddard, W. A., 3rd; Huang, Y.; Duan, X. Ultrafine jagged platinum nanowires enable ultrahigh mass activity for the oxygen reduction reaction. Science 2016, 354, 1414-1419. (161) Niu, Z.; Becknell, N.; Yu, Y.; Kim, D.; Chen, C.; Kornienko, N.; Somorjai, G. A.; Yang, P. Anisotropic phase segregation and migration of Pt in nanocrystals en route to nanoframe catalysts. Nat. Mater. 2016, 15, 11881194. (162) Jana, R.; Subbarao, U.; Peter, S. C. Ultrafast synthesis of flower-like ordered Pd3Pb nanocrystals with superior electrocatalytic activities towards oxidation of formic acid and ethanol. J. Power Sources 2016, 301, 160169. (163) Liu, X.; Wang, D.; Li, Y. Synthesis and catalytic properties of bimetallic nanomaterials with various architectures. Nano Today 2012, 7, 448-466. (164) Barth, S.; Boland, J. J.; Holmes, J. D. Defect transfer from nanoparticles to nanowires. Nano Lett. 2011, 11, 1550-1555. (165) Kang, Y.; Murray, C. B. Synthesis and electrocatalytic properties of cubic Mn-Pt nanocrystals (nanocubes). J. Am. Chem. Soc. 2010, 132, 7568-7569. (166) Yu, Z.; Zhang, J.; Liu, Z.; Ziegelbauer, J. M.; Xin, H.; Dutta, I.; Muller, D. A.; Wagner, F. T. Comparison between Dealloyed PtCo3 and PtCu3 Cathode Catalysts for Proton Exchange Membrane Fuel Cells. J. Phys. Chem. C 2012, 116, 19877-19885. (167) Lang, X.-Y.; Han, G.-F.; Xiao, B.-B.; Gu, L.; Yang, Z.-Z.; Wen, Z.; Zhu, Y.-F.; Zhao, M.; Li, J.-C.; Jiang, Q. Mesostructured Intermetallic Compounds of Platinum and Non-Transition Metals for Enhanced Electrocatalysis of Oxygen Reduction Reaction. Adv. Fun. Mater. 2015, 25, 230-237. (168) Wang, D.; Yu, Y.; Xin, H. L.; Hovden, R.; Ercius, P.; Mundy, J. A.; Chen, H.; Richard, J. H.; Muller, D. A.; DiSalvo, F. J. Tuning oxygen reduction reaction activity via controllable dealloying: a model study of ordered Cu3Pt/C intermetallic nanocatalysts. Nano Lett. 2012, 12, 5230-5238. (169) Wang, D.; Yu, Y.; Zhu, J.; Liu, S.; Muller, D. A.; Abruna, H. D. Morphology and activity tuning of Cu(3)Pt/C ordered intermetallic nanoparticles by selective electrochemical dealloying. Nano Lett. 2015, 15, 13431348. (170) Pavlišič, A.; Jovanovič, P.; Šelih, V. S.; Šala, M.; Bele, M.; Dražić, G.; Arčon, I.; Hočevar, S.; Kokalj, A.; Hodnik, N.; Gaberšček, M. Atomically Resolved Dealloying of Structurally Ordered Pt Nanoalloy as an Oxygen Reduction Reaction Electrocatalyst. ACS Catal. 2016, 6, 5530-5534. (171) Chen, M.; Liu, J.; Sun, S. One-step synthesis of FePt nanoparticles with tunable size. J. Am. Chem. Soc. 2004, 126, 8394-8395. (172) Chen, M.; Kim, J.; Liu, J.; Fan, H.; Sun, S. Synthesis of FePt nanocubes and their oriented self-assembly. J. Am. Chem. Soc. 2006, 128, 7132-7133. (173) Rong, H.; Mao, J.; Xin, P.; He, D.; Chen, Y.; Wang, D.; Niu, Z.; Wu, Y.; Li, Y. Kinetically Controlling Surface Structure to Construct Defect-Rich Intermetallic Nanocrystals: Effective and Stable Catalysts. Adv. Mater 2016 28, 2540-2546. (174) Kang, Y.; Pyo, J. B.; Ye, X.; Gordon, T. R.; Murray, C. B. shape control, and methanol electro-oxidation properties of Pt-Zn alloy and Pt3Zn intermetallic nanocrystals. ACS Nano 2012, 6, 5642-5647. (175) Chen, Q.; Zhang, J.; Jia, Y.; Jiang, Z.; Xie, Z.; Zheng, L. Wet chemical synthesis of intermetallic Pt3Zn nanocrystals via weak reduction reaction together with UPD process and their excellent electrocatalytic performances. Nanoscale 2014, 6, 7019-7024. (176) Bu, L.; Guo, S.; Zhang, X.; Shen, X.; Su, D.; Lu, G.; Zhu, X.; Yao, J.; Guo, J.; Huang, X. Surface engineering of hierarchical platinum-cobalt nanowires for efficient electrocatalysis. Nat. Commun. 2016, 7, 11850. (177) Luo, Z.; Ibanez, M.; Antolin, A. M.; Genc, A.; Shavel, A.; Contreras, S.; Medina, F.; Arbiol, J.; Cabot, A. Size and aspect ratio control of Pd(2)Sn nanorods and their water denitration properties. Langmuir 2015, 31, 39523957.
39 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
(178) Sun, D.; Si, L.; Fu, G.; Liu, C.; Sun, D.; Chen, Y.; Tang, Y.; Lu, T. Nanobranched porous palladium–tin intermetallics: One-step synthesis and their superior electrocatalysis towards formic acid oxidation. J. Power Sources 2015, 280, 141-146. (179) Liao, H.; Zhu, J.; Hou, Y. Synthesis and electrocatalytic properties of PtBi nanoplatelets and PdBi nanowires. Nanoscale 2014, 6, 1049-1055. (180) Maksimuk, S.; Yang, S.; Peng, Z.; Yang, H. Synthesis and characterization of ordered intermetallic PtPb nanorods. J. Am. Chem. Soc. 2007, 129, 8684-8685. (181) Wang, J.; Asmussen, R. M.; Adams, B.; Thomas, D. F.; Chen, A. Facile synthesis and electrochemical properties of intermetallic PtPb nanodendrites. Chem. Mater. 2009, 21, 1716-1724. (182) Wang, X.; Altmann, L.; Stöver, J.; Zielasek, V.; Bäumer, M.; Al-Shamery, K.; Borchert, H.; Parisi, J.; Kolny-Olesiak, J. Pt/Sn Intermetallic, Core/Shell and Alloy Nanoparticles: Colloidal Synthesis and Structural Control. Chem. Mater. 2013, 25, 1400-1407.
40 ACS Paragon Plus Environment
Page 40 of 41
Page 41 of 41
ACS Catalysis
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Paragon Plus Environment
