Kinetically Controlled Synthesis of Pt-Based One-Dimensional

Subscriber access provided by University of Otago Library

Article

Kinetically Controlled Synthesis of Pt-Based OneDimensional Hierarchically Porous Nanostructures with Large Mesopores as Highly Efficient ORR Catalysts Shaofang Fu, Chengzhou Zhu, Junhua Song, Mark H. Engelhard, Haibing Xia, Dan Du, and Yuehe Lin ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b11537 • Publication Date (Web): 01 Dec 2016 Downloaded from http://pubs.acs.org on December 9, 2016

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 free 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 accessible to all readers and 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.

ACS Applied Materials & Interfaces 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 21

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 Applied Materials & Interfaces

Kinetically Controlled Synthesis of Pt-Based OneDimensional Hierarchically Porous Nanostructures with Large Mesopores as Highly Efficient ORR Catalysts Shaofang Fu,a Chengzhou Zhu,*a Junhua Song,a Mark H Engelhard,b Haibing Xia,c Dan Du,a and Yuehe Lin*a,b a

The School of Mechanical and Materials Engineering, Washington State University, Pullman,

Washington 99164, United States. b

Pacific Northwest National Laboratory, Richland, WA 99352, USA

c

State Key Laboratory of Crystal Materials, Shandong University, Jinan, P. R. China

AUTHOR INFORMATION Corresponding Author *Chengzhou Zhu: [email protected]；*Yuehe Lin: [email protected] ABSTRACT

Rational design and construction of Pt-based porous nanostructures with large mesopores have triggered significant considerations because of their high surface area and more efficient mass transport. Hydrochloric acid-induced kinetically controlled reduction of metal precursors in the presence of soft template F-127 and hard template tellurium nanowires has been successfully

ACS Paragon Plus Environment

1


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 2 of 21

demonstrated to construct one-dimensional hierarchical porous PtCu alloy nanostructures with large mesopores. Moreover, the electrochemical experiments demonstrated that the PtCu hierarchically porous nanostructures synthesized under optimized condition exhibit enhanced electrocatalytic performance for oxygen reduction reaction in acid media.

Keyword: porous nanostructures, one-dimensional nanomaterials, kinetically controlled synthesis, Pt alloys, oxygen reduction reaction Introduction Porous noble metal nanostructures (PNMNs) are attracting considerable interest in many fields including electrocatalysis, energy storage, and sensors owing to their large surface area, abundant active sites and high porosity.1-4 Great contributions have been made to synthesize PNMNs with well-controlled structural characteristics using diversified strategies, such as dealloying techniques,5,6 self-assembly,7,8 galvanic replacement reactions9,10 and templating methods.11,12 Among them, templating methods using hard or/and soft templates are considered as one of the most efficient approaches to synthesize PNMNs, which are greatly benefiting from abundant kinds of template materials with profuse porosity. A typical example is that Yamauchi’s group has successfully synthesized a large variety of PNMNs using different templates by electrochemical or chemical reduction method, such as mesoporous Au and Pd films,13,14 mesoporous Pt nanoparticles (NPs)12,15 and mesoporous Pt nanorods.16 It is noticed that most of the reported PNMNs are limited to NPs with irregular shapes or to continuous films. Also, relatively small pores involved, i.e., micropores and mesopores with small sizes, significantly contribute to surface area but severely limit mass transport and thus lower their applied performances.17-19 Elaborately controlling the PNMNs with large mesopores as well as


2

Page 3 of 21

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 active sites are indeed challenging for the material design.20,21 Under the circumstances, the integrated control of morphology and pore size of the PNMNs are believed to be an important subject for the development of more complex nanomaterials, further expanding their potential applications. Pt-based PNMNs have attracted increasing interests for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs).22-25 In addition to size and porous structure effects, current studies demonstrate Pt-based bimetallic/multimetallic alloys can significantly improve ORR electrocatalytic activity compared to the monometallic Pt. Among them, alloying Pt with first-row transition metals, such as Fe, Co, Ni, and Cu, has been demonstrated as an efficient approach toward advanced ORR nanocatalysts owing to the electronic and geometric effects.26-30 One of the efficient approaches for further enhancing ORR performance is constructing one-dimensional (1D) Pt-based nanostructures, endowing them with appealing attributes including anisotropic morphology, preferential exposure of highly active crystal facets, and easy electron transport.31-34 Combining the synergistic effects between these structural and compositional features, constructing 1D nanomaterials with porous nanostructures and optimized compositions are expected to achieve improved electrocatalytic ORR performance.

Scheme 1. Synthesis procedure of PtCu ODHMNs.


3


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 21

Based on our previous work,35 where PtCu bimetallic nanotubes with enhanced electrocatalytic performance for ORR were synthesized using Te nanowires (NWs) as hard template, we introduced Pluronic F-127 as soft template to form large mesopores on the surface of the nanotubes. As illustrated in Scheme 1, the kinetically controlled synthesis of PtCu 1D hierarchical mesoporous nanostructures (ODHMNs) with large mesopores was proposed using Te NWs and Pluronic F-127 as dual templates in aqueous solution. Under the typical synthesis condition, Te NWs serve as hard templates and enable the evolution of 1D nanostructures, while hydrochloric acid-induced kinetically controlled reduction of metal precursors in the presence of soft template F-127 plays a critical role in the formation of PtCu hierarchically porous nanostructures, featured by uniform mesopores with large pore size. Moreover, the as-prepared PtCu ODHMNs with optimized composition exhibited enhanced electrocatalytic activity and durability for ORR in acid solutions, holding great promise in PEMFCs. Results and discussions


4

Page 5 of 21

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 1. SEM (A and B), TEM (C and D), SAED pattern (D inset), and HRTEM (E) images of Pt72Cu28 ODHMNs. Elemental mapping images of PtCu (F), Pt (G) and Cu (H) in Pt72Cu28 ODHMNs, and the corresponding line-scan analysis (I). Several reported works have demonstrated the formation of 1D Pt-based nanostructures using Te as sacrificial template.4 In this work, F-127, ascorbic acid and HCl were introduced to obtain the 1D hierarchical structures. The morphology of the resultant product was first investigated by scanning electron microscope (SEM) and transmission electron microscopy (TEM). As shown in Figure 1A-D, it is clearly observed that the Pt72Cu28 ODHMNs are fairly uniform in size (with an average diameter of ~ 107.3 nm) and shape without other byproducts. The high magnification TEM image confirms the formation of mesopores as revealed in Figure 1D. Close observation shows that the concaved large mesopores with the size of ~ 10 nm are uniformly dispersed within ODHMNs. Selected-area electron diffraction (SAED) pattern (Figure 1D inset) reveals the intense spots, indicating the polycrystalline structure of PtCu ODHMNs. High-resolution TEM (HRTEM) image in Figure 1E reveals that the entire PtCu ODHMNs are composed of interconnected nanodendrites with a lattice distance of 0.22 nm, corresponding to (111) planes of face-centered cubic (fcc) PtCu alloys. Based on morphological characterizations, typical hierarchical structures including nanodendrite surface and large pore-induced hollow structures were confirmed. Figure 1F-H show the elemental mapping of Pt72Cu28 ODHMNs, indicating the uniform distribution of Pt and Cu throughout the ODHMNs. Furthermore, the intensity profile was carried out to characterize the elements distribution across Pt72Cu28 ODHMNs (Figure 1I), confirming that both Pt and Cu are uniformly distributed. These analyses prove that PtCu crystalline alloys were formed through the entire ODHMNs instead of mixed metallic Pt and Cu.


5


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 6 of 21

Additionally, the energy dispersive X-ray spectrum (EDS) of prepared Pt72Cu28 ODHMNs in Figure S1A demonstrates the complete decomposition of Te templates. To shed light on the formation mechanism of the ODHMNs, the roles of F-127 and HCl were investigated. As shown in Figure S1B and S2, only PtCu dendritic NWs with the size of ~25.7 and 38.1 nm were observed without the addition of F-127 or HCl, respectively. No obvious large pores were generated for the both cases. Normally, Pt nanodendrites with narrow interspaces of less than 5 nm were obtained with the assistance of surfactants and other reagents (e.g., F-127 and AA) through fast reduction reactions.36,37 Recent advances show that the reduction kinetics of precursors is closely associated with their structural characteristics, which can be effectively tailored by the reduction ability of the reducing agent or reduction potential of metal precursors.21,38-40 Due to the introduction of HCl here, the reduction ability of AA significantly decreases and the extremely slow reduction rate was caused, which is responsible for the evolution of well-defined mesoporous nanostructures.21 In detail, the concentration of F-127 adopted is higher than its critical micelle concentration, the spherical micelles are formed with poly(propylene oxide) (PPO) core and poly(ethylene oxide) (PEO) shell. Owing to the interaction between PPO groups of F-127 and metal surface, F-127 micelles adhering to primarily reduced metals serve as stabilizer to prevent the aggregation of metal particles. The acidic condition decreases the reduction rate of metal precursors, which is favorable for the retention of F-127 micelle arrangement to the utmost extent during adhering to primarily reduced metals and the subsequent evolution of the large mesopores. We next assessed the role of Te NWs on the morphology of PtCu alloys. As shown in Figure S3, NPs with concaved surface are obtained without the addition of Te templates, which agree well with the previous report.21 We can expect that this strategy might be universal for the synthesis


6

Page 7 of 21

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


of mesoporous nanostructures with other shapes by replacing the templates. It should be noted that Te NWs not only serve as hard template but also act as reducing agent, which can be completely decomposed and directly diffused into reaction solution.32 Interestingly, the diameter and morphology of PtCu ODHMNs could be easily controlled by varying the concentration of Te NWs. As shown in Figure S4 and S5, similar ODHMNs with large mesopores could be clearly observed with the addition of 0.15 and 0.3 mL Te NWs. As the amount of template goes up to 0.6 and 1.2 mL, only dendritic NWs with gradually decreased diameter are obtained because the concentration of metal precursors is not high enough to form mesopores.

Figure 2. TEM images of Pt60Cu40 (A) and Pt80Cu20 (B) ODHMNs under typical synthesis condition. Besides the contributions from F-127, HCl and Te, we also examined the role of precursor concentration on the formation of PtCu ODHMNs. When the ratio of Pt and Cu precursors was adjusted to 1:1 and 3:1, Pt60Cu40 and Pt80Cu20 ODHMNs with well-defined large pores were obtained (Figure 2). It is worth noting that the atomic percentages of Pt in final products are higher than those in the precursors due to the higher standard reduction potential of (PtCl6)2-/Pt compared to Cu2+/Cu. An additional experiment was also conducted using the typical procedure but without Pt precursor. No Cu nanostructures were obtained (Figure S6), indicating that


7


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 8 of 21

underpotential deposition of Cu instead of co-reduction triggered the formation of PtCu alloy due to the mild reductive capability of AA. Interestingly, only Pt dendritic NWs were formed when H2PtCl6 was used as the only precursor (Figure S7), further confirming the structure directing function of Cu atoms. Taken together, all the reaction parameters including dual templates, HCl and Cu precursors are indispensable for the construction of the PtCu ODHMNs with welldefined large mesopores.

Figure 3. (A) XRD spectra of Pt nanodendrites (a), and Pt80Cu20 (b), Pt72Cu28 (c), Pt60Cu40 (d) ODHMNs (blue: Pt, red: Cu). (B) XPS spectrum of Pt72Cu28 ODHMNs. (C) High resolution Pt 4f XPS spectra of Pt nanodendrites and PtCu ODHMNs. (D) High resolution Pt 4f XPS spectra of Pt72Cu28 ODHMNs. Figure 3A shows the representative X-ray diffraction (XRD) patterns of PtCu ODHMNs and Pt nanodendrites. The distinct peaks can be assigned to (111), (200), (220), and (311) planes of fcc


8

Page 9 of 21

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


crystal structures, which is consistent with SEAD pattern. A shift of peak position can be observed clearly on PtCu ODHMNs relative to Pt nanodendrites, indicating the formation of PtCu alloys. To investigate their surface composition, X-ray photoelectron spectroscopy (XPS) analysis shows strong Pt and Cu peaks in PtCu ODHMNs (Figure 3B and S8). Moreover, a slight shift of Pt and Cu peaks can be observed in Figure 3C and S8C, which further confirms the formation of PtCu alloys. The high resolution Pt 4f XPS spectrum of Pt72Cu28 ODHMNs in Figure 3D shows two strong peaks at 71.4 and 74.8 eV, corresponding to Pt 4f7/2 and Pt 4f5/2. They were further deconvoluted into four peaks at ~ 71.3, 72.2, 74.9, and 76.7 eV, suggesting the presence of Pt (0) and Pt (II) on the surface of the PtCu ODHMNs. Based on their peak areas, metallic Pt is the dominant composition on the surface of PtCu ODHMNs, which is beneficial for the electrocatalysis of ORR.


9


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 10 of 21

Figure 4. CV curves (A) and hydroxyl surface coverage (B) of Pt72Cu28 ODHMNs, Pt nanodendrites and commercial Pt/C catalysts in N2-saturated 0.1 M HClO4 solution. LSV curves (C) and the corresponding Tafel plots (D) of Pt72Cu28 ODHMNs, Pt nanodendrites and commercial Pt/C catalysts in O2-saturated 0.1 M HClO4 solution. (E) MA and SA of Pt72Cu28 ODHMNs, Pt nanodendrites and commercial Pt/C catalysts at 0.85 V. (F) ECSA and MA changes of Pt72Cu28 ODHMNs and Pt/C during stability tests. The electrochemical ORR experiments were performed in a glassy carbon rotating disk electrode (RDE). Figure 4A and S9A show the cyclic voltammetry (CV) curves of PtCu ODHMNs, Pt nanodendrites and commercial Pt/C catalyst. According to these CV curves, the ECSA of as-


10

Page 11 of 21

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


prepared samples and commercial Pt/C could be estimated through measuring the total charge collected in hydrogen adsorption and desorption region. Assuming a coulombic charge of 210 µC/cm2, the ECSAs of Pt60Cu40, Pt72Cu28 and Pt80Cu20 ODHMNs are 74.6, 73.1, and 70.2 m2/g, respectively, which are close to that of commercial Pt/C catalyst. Compared to the Pt nanodendrites, the higher ECSA of PtCu ODHMNs is attributed to their particular hierarchical mesoporous nanostructures and the compositional advantages. It is worth noting that the Ptbased catalysts also present different abilities to adsorb/desorb hydroxyl species (OHad). As illustrated in Figure 4A, there are obvious positive shift of hydroxyl adsorption/desorption peaks on PtCu ODHMNs and Pt nanodendrites compared to Pt/C catalyst, which demonstrates the slower hydroxyl adsorption rate and faster hydroxyl desorption rate on PtCu ODHMNs and Pt nanodendrites, and thus resulting in a better ORR activity. In comparison with commercial Pt/C, the PtCu ODHMNs and Pt nanodendrites display lower fractional coverage of hydroxyl (ΘOHad) in Figure 4B, which also contribute the enhanced ORR catalytic activity.41,42 ORR electrocatalytic performances of PtCu ODHMNs, Pt nanodendrites as well as commercial Pt/C were investigated and the results are summarized in Table 1. According to the linear sweep voltammetry (LSV) curves provided in Figure 4C and S9B, it is apparent that ORR activity is highly dependent on the morphology and composition of catalysts. We found the optimized Pt72Cu28 ODHMNs possessed the most positive onset potential and half-wave potential, which are also advantageous over those Pt nanodendrites and commercial Pt/C. As expected, the Pt72Cu28 ODHMNs present the smallest Tafel slope of only 89 mV/decade compared to other counterparts and Pt/C (Figure 4D and S9C), confirming their enhanced ORR electrocatalytic activities. To better understand the mass and surface effects, the mass activity (MA) and specific activity (SA) were calculated, which were normalized by the loading amount of Pt and ECSA,


11


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 12 of 21

respectively. As illustrated in Figure 4E and Table 1, a MA of 0.31 A/mgPt for optimized Pt72Cu28 ODHMNs is almost 5 and 2.6 times higher than that of Pt nanodendrites (0.06 A/mgPt) and Pt/C (0.12 A/mgPt) at 0.85 V, respectively. As such, Pt72Cu28 ODHMNs also present a higher SA (0.42 mA/cm2) than those of Pt nanodendrites (0.12 mA/cm2) and Pt/C (0.15 mA/cm2). Table 1. Electrochemical parameters of PtCu ODHMNs, Pt nanodendrites, and commercial Pt/C catalyst. Onset

Half-wave

ECSA (m2/g)

Tafel slope MA (A/mgPt)

potential (V)

potential (V)

SA (mA/cm2) (mV/decade)

Pt60Cu40

74.6

0.883

0.791

0.08

0.11

104

Pt72Cu28

73.1

0.931

0.853

0.31

0.42

89

Pt80Cu20

70.2

0.902

0.82

0.15

0.21

96

Pt

32.2

0.882

0.763

0.06

0.2

139

Pt/C

83

0.924

0.811

0.12

0.15

98

In order to evaluate the durability of the PtCu ODHMNs for ORR, the accelerated degradation test (ADT) was conducted and ECSA loss was calculated and illustrated in Figure 4F. It can be seen that Pt72Cu28 ODHMNs exhibit a slight loss of 4% in ECSA after 1000 cycles, while the commercial Pt/C presents a significant loss of 37%. After 5000 cycles, there is only a drop of 18% in ECSA for Pt72Cu28 ODHMNs, but a substantial loss of 54% for Pt/C, indicating the better durability of Pt72Cu28 ODHMNs relative to Pt/C. The LSV curves of Pt72Cu28 ODHMNs and


12

Page 13 of 21

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


Pt/C were also recorded during the cyclic potential sweep (Figure S10C and D). There is a negative shift of 18 and 30 mV in half-wave potential for Pt72Cu28 ODHMNs and commercial Pt/C, respectively. Moreover, 68% of MA remained for Pt72Cu28 ODHMNs after ADT (Figure 4F). In contrast, there was only 50% of MA left for Pt/C, confirming the better long-term stability of Pt72Cu28 ODHMNs. TEM images in Figure S11 reveal that the hierarchical nanostructures of PtCu ODHMNs were well maintained after 5000 cycles, while Pt/C catalyst showed significant aggregations, confirming the better stability of PtCu ODHMNs. The enhanced electrocatalytic performance of PtCu ODHMNs should be attributed to several factors. (a) The introduction of Cu causes the downshift of the d-band center of Pt in the alloy structure, which could weaken the binding of hydroxyl species to Pt and thus increase ORR activity. (b) The hierarchical porous nanostructures play a core role in ORR activity and durability. On the one hand, the large and uniform mesopores on the surface of PtCu ODHMNs and their hollow interior can not only afford more accessible surface area for high Pt utilization but facilitate gas diffusion and mass transport. On the other hand, 1D morphology is less vulnerable to catalysts aggregation/dissolution and carbon corrosion. (c) The elimination of carbon support ensures the direct contact between the gas diffusion layer and catalyst layer, which can not only facilitate the mass transport but increase the Pt utilization.2,43 Conclusion In summary, the novel PtCu ODHMNs were successfully synthesized via hydrochloric acidinduced kinetically controlled reduction of metal precursors in the presence of dual templates. The mesopores with large pore size were uniformly distributed within PtCu ODHMNs. By carefully tuning the composition of PtCu alloys, the as-prepared PtCu ODHNMs exhibited


13


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 14 of 21

enhanced electrocatalytic performance for ORR due to the synergistic effects between structural and compositional attributes. This facile strategy is expected to be feasible for the synthesis of other nanomaterials with various shapes and compositions. ASSOCIATED CONTENT Supporting Information TEM image of porous Pt72Cu28 alloys without addition of F-127 or HCl under typical synthesis condition, SEM and TEM images of PtCu mesoporous NPs, SEM and TEM images of PtCu ODHMNs with 0.15, 0.3, 0.6, and 1.2 mL Te NWs solutions under typical synthesis condition, digital picture of sample without the addition of Pt precursor under typical synthesis condition, TEM image of Pt nanodendrites under typical synthesis condition, CV curves of Pt60Cu40, Pt72Cu28, Pt80Cu20 ODHMNs, Pt nanodendrites and commercial Pt/C catalysts in N2-saturated 0.1 M HClO4 solution, the LSV curves and corresponding Tafel plots in O2-saturated 0.1 M HClO4 solution, CV and LSV curves of Pt72Cu28 ODHMNs and Pt/C during ADT tests, TEM images of Pt/C and Pt72Cu28 ODHMNs before and after ADT. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *Email: [email protected]; [email protected] Notes Authors have no financial interests.


14

Page 15 of 21

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


ACKNOWLEDGMENT This work was supported by a start-up fund of Washington State University, USA. The XPS analysis was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We thank Franceschi Microscopy & Image Center at Washington State University for TEM and SEM measurements. REFERENCES 1. Malgras, V.; Ataee-Esfahani, H.; Wang, H.; Jiang, B.; Li, C.; Wu, K. C. W.; Kim, J. H.; Yamauchi, Y. Nanoarchitectures for Mesoporous Metals. Adv. Mater. 2016, 28, 993-1010. 2. Zhu, C.; Du, D.; Eychmüller, A.; Lin, Y. Engineering Ordered and Nonordered Porous Noble Metal Nanostructures: Synthesis, Assembly, and Their Applications in Electrochemistry. Chem. Rev. 2015, 115, 8896-8943. 3. Li, Y.; Bastakoti, B. P.; Malgras, V.; Li, C.; Tang, J.; Kim, J. H.; Yamauchi, Y. Polymeric Micelle Assembly for the Smart Synthesis of Mesoporous Platinum Nanospheres with Tunable Pore Sizes. Angew. Chem., Int. Ed. 2015, 54, 11073-11077. 4. Zhu, C.; Shi, Q.; Fu, S.; Song, J.; Xia, H.; Du, D.; Lin, Y., Efficient Synthesis of MCu (M = Pd, Pt, and Au) Aerogels with Accelerated Gelation Kinetics and their High Electrocatalytic Activity. Adv. Mater. 2016, 28, 8779-8783. 5. Qi, Z.; Weissmüller, J. Hierarchical Nested-Network Nanostructure by Dealloying. ACS Nano 2013, 7, 5948-5954. 6. Oezaslan, M.; Heggen, M.; Strasser, P. Size-Dependent Morphology of Dealloyed Bimetallic Catalysts: Linking the Nano to the Macro Scale. J. Am. Chem. Soc. 2012, 134, 514-524.


15


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 16 of 21

7. Warren, S. C.; Messina, L. C.; Slaughter, L. S.; Kamperman, M.; Zhou, Q.; Gruner, S. M.; DiSalvo, F. J.; Wiesner, U. Ordered Mesoporous Materials from Metal Nanoparticle–Block Copolymer Self-Assembly. Science 2008, 320, 1741752. 8. Bigall, N. C.; Herrmann, A. K.; Vogel, M.; Rose, M.; Simon, P.; Carrillo-Cabrera, W.; Dorfs, D.; Kaskel, S.; Gaponik, N.; Eychmüller, A. Hydrogels and Aerogels from Noble Metal Nanoparticles. Angew. Chem., Int. Ed. 2009, 48, 9731-9734. 9. Xia, X.; Wang, Y.; Ruditskiy, A.; Xia, Y. Galvanic Replacement: A Simple and Versatile Route to Hollow Nanostructures with Tunable and Well-Controlled Properties. Adv. Mater. 2013, 25, 6313-6333. 10. Zhang, H.; Jin, M.; Liu, H.; Wang, J.; Kim, M. J.; Yang, D.; Xie, Z.; Liu, J.; Xia, Y. Facile Synthesis of Pd–Pt Alloy Nanocages and Their Enhanced Performance for Preferential Oxidation of CO in Excess Hydrogen. ACS Nano 2011, 5, 8212-8222. 11. Hsueh, H. Y.; Chen, H. Y.; Hung, Y. C.; Ling, Y. C.; Gwo, S.; Ho, R. M. Well-Defined Multibranched Gold with Surface Plasmon Resonance in Near-Infrared Region from Seeding Growth Approach Using Gyroid Block Copolymer Template. Adv. Mater. 2013, 25, 1780-1786. 12. Wang, H.; Jeong, H. Y.; Imura, M.; Wang, L.; Radhakrishnan, L.; Fujita, N.; Castle, T.; Terasaki, O.; Yamauchi, Y. Shape- and Size-Controlled Synthesis in Hard Templates: Sophisticated Chemical Reduction for Mesoporous Monocrystalline Platinum Nanoparticles. J. Am. Chem. Soc. 2011, 133, 14526-14529. 13. Li, C.; Dag, Ö.; Dao, T. D.; Nagao, T.; Sakamoto, Y.; Kimura, T.; Terasaki, O.; Yamauchi, Y. Electrochemical Synthesis of Mesoporous Gold Films toward Mesospace-Stimulated Optical Properties. Nat. Commun. 2015, 6, 6608.


16

Page 17 of 21

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


14. Li, C.; Jiang, B.; Miyamoto, N.; Kim, J. H.; Malgras, V.; Yamauchi, Y. Surfactant-Directed Synthesis of Mesoporous Pd Films with Perpendicular Mesochannels as Efficient Electrocatalysts. J. Am. Chem. Soc. 2015, 137, 11558-11561. 15. Karthika, P.; Ataee-Esfahani, H.; Wang, H.; Francis, M. A.; Abe, H.; Rajalakshmi, N.; Dhathathreyan, K. S.; Arivuoli, D.; Yamauchi, Y. Synthesis of Mesoporous Pt–Ru Alloy Particles with Uniform Sizes by Sophisticated Hard-Templating Method. Chem. Asian J. 2013, 8, 902-907. 16. Li, C.; Sato, T.; Yamauchi, Y. Electrochemical Synthesis of One-Dimensional Mesoporous Pt Nanorods Using the Assembly of Surfactant Micelles in Confined Space. Angew. Chem., Int. Ed. 2013, 52, 8050-8053. 17. Wang, H.; Ishihara, S.; Ariga, K.; Yamauchi, Y. All-Metal Layer-by-Layer Films: Bimetallic Alternate Layers with Accessible Mesopores for Enhanced Electrocatalysis. J. Am. Chem. Soc. 2012, 134, 10819-10821. 18. Chen, P. K.; Lai, N. C.; Ho, C. H.; Hu, Y. W.; Lee, J. F.; Yang, C. M. New Synthesis of MCM-48 Nanospheres and Facile Replication to Mesoporous Platinum Nanospheres as Highly Active Electrocatalysts for the Oxygen Reduction Reaction. Chem. Mater. 2013, 25, 4269-4277. 19. Shin, H. J.; Ryoo, R.; Liu, Z.; Terasaki, O. Template Synthesis of Asymmetrically Mesostructured Platinum Networks. J. Am. Chem. Soc. 2001, 123, 1246-1247. 20. Ataee-Esfahani, H.; Liu, J.; Hu, M.; Miyamoto, N.; Tominaka, S.; Wu, K. C. W.; Yamauchi, Y. Mesoporous Metallic Cells: Design of Uniformly Sized Hollow Mesoporous Pt–Ru Particles with Tunable Shell Thicknesses. Small 2013, 9, 1047-1051. 21. Jiang, B.; Li, C.; Imura, M.; Tang, J.; Yamauchi, Y. Multimetallic Mesoporous Spheres Through Surfactant-Directed Synthesis. Adv. Sci. 2015, 2, 1500112.


17


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 18 of 21

22. Debe, M. K. Electrocatalyst Approaches and Challenges for Automotive Fuel Cells. Nature 2012, 486, 43-51. 23. Kibsgaard, J.; Gorlin, Y.; Chen, Z.; Jaramillo, T. F. Meso-Structured Platinum Thin Films: Active and Stable Electrocatalysts for the Oxygen Reduction Reaction. J. Am. Chem. Soc. 2012, 134, 7758-7765. 24. Guo, S.; Zhang, S.; Sun, S. Tuning Nanoparticle Catalysis for the Oxygen Reduction Reaction. Angew. Chem., Int. Ed. 2013, 52, 8526-8544. 25. Chen, C.; Kang, Y.; Huo, Z.; Zhu, Z.; Huang, W.; Xin, H. L.; Snyder, J. D.; Li, D.; Herron, J. A.; Mavrikakis, M.; Chi, M.; More, K. L.; Li, Y.; Markovic, N. M.; Somorjai, G. A.; Yang, P.; Stamenkovic, V. R. Highly Crystalline Multimetallic Nanoframes with Three-Dimensional Electrocatalytic Surfaces. Science 2014, 343, 1339-1343. 26. Fu, S.; Zhu, C.; Du, D.; Lin, Y. Enhanced Electrocatalytic Activities of PtCuCoNi ThreeDimensional Nanoporous Quaternary Alloys for Oxygen Reduction and Methanol Oxidation Reactions. ACS Appl. Mater. Interfaces 2016, 8, 6110-6116. 27. Greeley, J.; Stephens, I. E. L.;

Bondarenko, A. S.; Johansson, T. P.; Hansen, H. A.;

Jaramillo, T. F. Rossmeisl, J.; Chorkendorff, I.; Nørskov, J. K. Alloys of Platinum and Early Transition Metals as Oxygen Reduction Electrocatalysts. Nat. Chem. 2009, 1, 552-556. 28. Guo, S.; Li, D.; Zhu, H.; Zhang, S.; Markovic, N. M.; Stamenkovic, V. R.; Sun, S. FePt and CoPt Nanowires as Efficient Catalysts for the Oxygen Reduction Reaction. Angew. Chem., Int. Ed. 2013, 52, 3465-3468. 29. Huang, X.; Zhu, E.; Chen, Y.; Li, Y.; Chiu, C. Y.; Xu, Y.; Lin, Z.; Duan, X.; Huang, Y. A Facile Strategy to Pt3Ni Nanocrystals with Highly Porous Features as an Enhanced Oxygen Reduction Reaction Catalyst. Adv. Mater. 2013, 25, 2974-2979.


18

Page 19 of 21

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


30. Wittkopf, J. A.; Zheng, J.; Yan, Y. High-Performance Dealloyed PtCu/CuNW Oxygen Reduction Reaction Catalyst for Proton Exchange Membrane Fuel Cells. ACS Catal. 2014, 4, 3145-3151. 31. Zhu, H.; Zhang, S.; Guo, S.; Su, D.; Sun, S. Synthetic Control of FePtM Nanorods (M = Cu, Ni) To Enhance the Oxygen Reduction Reaction. J. Am. Chem. Soc. 2013, 135, 7130-7133. 32. Hong, W.; Wang, J.; Wang, E. Facile Synthesis of PtCu Nanowires with Enhanced Electrocatalytic Activity. Nano Res. 2015, 8, 2308. 33. Liu, W.; Rodriguez, P.; Borchardt, L.; Foelske, A.; Yuan, J.; Herrmann, A. K.; Geiger, D.; Zheng, Z.; Kaskel, S.; Gaponik, N.; Kötz, R.; Schmidt, T. J.; Eychmüller, A. Bimetallic Aerogels: High-Performance Electrocatalysts for the Oxygen Reduction Reaction. Angew. Chem., Int. Ed. 2013, 52, 9849-9852. 34. Zhu, C.; Guo, S.; Dong, S. PdM (M = Pt, Au) Bimetallic Alloy Nanowires with Enhanced Electrocatalytic Activity for Electro-oxidation of Small Molecules. Adv. Mater. 2012, 24, 23262331. 35. Fu, S.; Zhu, C.; Shi, Q.; Du, D.; Lin, Y. PtCu Bimetallic Alloy Nanotubes with Porous Surface for Oxygen Reduction Reaction. RSC Adv. 2016, 6, 69233-69238. 36. Wang, L.; Yamauchi, Y. Block Copolymer Mediated Synthesis of Dendritic Platinum Nanoparticles. J. Am. Chem. Soc. 2009, 131, 9152-9153. 37. Wang, L.; Hu, C.; Nemoto, Y.; Tateyama, Y.; Yamauchi, Y. On the Role of Ascorbic Acid in the Synthesis of Single-Crystal Hyperbranched Platinum Nanostructures. Cryst. Growth Des. 2010, 10, 3454-3460.


19


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 20 of 21

38. Li, H.; Ma, S.; Fu, Q.; Liu, X.; Wu, L.; Yu, S. Scalable Bromide-Triggered Synthesis of Pd@Pt Core–Shell Ultrathin Nanowires with Enhanced Electrocatalytic Performance toward Oxygen Reduction Reaction. J. Am. Chem. Soc. 2015, 137, 7862-7868. 39. Jiang, B.; Li, C.; Malgras, V.; Imura, M.; Tominaka, S.; Yamauchi, Y. Mesoporous Pt Nanospheres with Designed Pore Surface as Highly Active Electrocatalyst. Chem. Sci. 2016, 7, 1575-1581. 40. Xia, B.; Wu, H.; Wang, X.; Lou, X. One-Pot Synthesis of Cubic PtCu3 Nanocages with Enhanced Electrocatalytic Activity for the Methanol Oxidation Reaction. J. Am. Chem. Soc. 2012, 134, 13934-13937. 41. Zhang, G.; Sun, S.; Cai, M.; Zhang, Y.; Li, R.; Sun, X. Porous Dendritic Platinum Nanotubes with Extremely High Activity and Stability for Oxygen Reduction Reaction. Sci. Rep. 2013, 3, 1526. 42. Peng, Z.; Yang, H. Synthesis and Oxygen Reduction Electrocatalytic Property of Pt-on-Pd Bimetallic Heteronanostructures. J. Am. Chem. Soc. 2009, 131, 7542-7543. 43. Sun, S.; Zhang, G.; Geng, D.; Chen, Y.; Li, R.; Cai, M.; Sun, X. A Highly Durable Platinum Nanocatalyst for Proton Exchange Membrane Fuel Cells: Multiarmed Starlike Nanowire Single Crystal. Angew. Chem. Int. Ed. 2011, 50, 422-426.


20

Page 21 of 21

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


Table of Content


21

Kinetically Controlled Synthesis of Pt-Based One-Dimensional

Recommend Documents