Ir-Alloyed Ultrathin Ternary PdIrCu Nanosheet-Constructed Flower

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Energy, Environmental, and Catalysis Applications

Ir-Alloyed Ultrathin Ternary PdIrCu NanosheetsConstructed Flower with Greatly Enhanced Catalytic Performance towards Formic Acid Electrooxidation Hong Ming An, Zhi Liang Zhao, Lian Ying Zhang, Yue Chen, Yan Yan Chang, and Chang Ming Li ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b13361 • Publication Date (Web): 06 Nov 2018 Downloaded from http://pubs.acs.org on November 7, 2018

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ACS Applied Materials & Interfaces

Ir-Alloyed Ultrathin Ternary PdIrCu NanosheetsConstructed Flower with Greatly Enhanced Catalytic Performance towards Formic Acid Electrooxidation Hong Ming An,‡a,b Zhi Liang Zhao,‡a,c Lian Ying Zhang,d Yue Chen,a Yan Yan Changa and Chang Ming Li*a,c a

Institute for Clean Energy & Advanced Materials, Faculty of Materials & Energy, Southwest

University, Chongqing 400715, China. b

Guizhou Space Appliance Co., Ltd, Guiyang 550009, China.

c

Institute of Materials Science & Devices, Suzhou University of Science & Technology, Suzhou

215009, China. d

‡

Institute of Materials for Energy & Environment, Qingdao University, Qingdao 266071, China. Hong Ming An and Zhi Liang Zhao contributed equally to this work.

KEYWORDS: Formic acid electrooxidation, Ultrathin, Ternary, PdIrCu, Nanosheets ABSTRACT: Ternary metal-elements alloys have been reported as efficient electrocatalyst towards various electrochemical reactions but a unique 3-dimensional Ir-alloyed ternary nanosheets-composed flower (NCF) structure has not been explored yet. Herein, an innovated 1.8

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nm Ir-alloyed ultrathin ternary PdIrCu NCF structure is synthesized via one-pot solvothermal reduction without using any surfactant. The as-prepared PdIrCu/C NCF catalyst remarkably improves the stability than commercial Pd/C towards formic acid electrooxidation (FAO) while resulting in significant increase mass activity. The electrocatalytic properties improvement denpends on the introduction of Ir and Cu atoms, which greatly prevented poisoning from CO while modifying electronic structure of Pd for increased reaction active sites and accelerated charge transfer rate as well as facilitated mass transport by ultrathin NCF 3D structure. Therefore, this catalyst possesses a promising application prospect in electrochemical energy storage/conversion systems. 1. INTRODUCTION

Fuel cell is regarded as the most promising clean energy, which has been received increasing attention due to it has many advantages, such as high power generation efficiency, low environment pollution and wide range sources of fuels1, 2. It is known that Pd has been considered to be an up-and-coming anode catalyst for such fuel cells resulted in part from it posseses similar properties to Pt, and its cost is lower than that of Pt3-7. Especially in direct formic acid fuel cells (DFAFCs), Pd surface is extremely easy to adsorb formic acid molecules to generate HCOO* intermediate product, and then HCOO* is transformed directly to CO2 via two-electron reaction pathway8, 9, thus inhibiting the CO poisoning that often occurs on Pt surface. However, Pd is easily attacked by acid and is not very stable in acidic electrolyte. Another concern is that non-abundant Pd cannot support large-scale applications. Pd-based alloys have been extensively studied as alternative catalysts to reduce the usage of Pd10-12. The main challenges mainly are how to achieve high electroactivity and operation stability. Engineering rational nanostructures of the Pd alloys to maximize or/and expose the number of active sites can greatly improve the electrocatalytic performances while reducing Pd usage13-17.


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Various Pd-based alloys such as PdCo, PdNi, PdCu or PdAg have been extensively studied and applied in catalytic reactions11, 14-21. Although binary Pd-based alloy is an effective strategy, its performance still cannot meet the needs of the commercialization thus demanding further significant improvement. It is reported that metal Ir possesses exceptional stability in acidic medium thanks to high redox potential. Besides, Ir is easily to produce -OH functional group at low potential to prevent poisoning from CO for the remarkably improved catalyst activity and stability22-25. Accordingly, for the first time we prepared Ir-alloyed ultrathin ternary PdIrCu NCF by a facile one pot solvothermal reduction without using any surfactant. In the process of preparation, Cu with Ir atoms co-modification the electronic structure of Pd simultaneous production an unparalleled ultrathin NCF structure. Results exhibit that the prepared PdIrCu/C NCF catalyst significantly enhances the electrocatalytic performance compared to commercial Pd/C, thus it possesses a promising future applications in energy storage/conversion systems. 2. EXPERIMENTAL SECTION 2.1. Materials. Sodium tetrachloropalladate (Na2PdCl4,98%), cupric chloride anhydrous (CuCl2.2H2O, 99.99%), tungsten hexacarbonyl (C6O6W, 99.9%), acetic acid (C2H4O2, ≥99.8%), hexachloroiridium acid hydrate (H2IrCl6·хH2O, ≥36%) and N, N-dimethylformamide (DMF) were bought from Aladdin Inc. Nafion (5wt %, Sigma-Aldrich) and commercial Pd/C (30wt %, Sigma-Aldrich) were used. Ethanol and sulfuric acid were bought from Chongqing Chuandong Chemical (group) Co. Ltd and Chengdu Kelon Chemical Reagent Factory, respectively. 2.2. Preparation of PdCu and PdIrCu NCF. A typical procedure is as following: Na2PdCl4 (10 mg), W(CO)6 (50 mg) and CuCl2.2H2O (10 mg) were added a 20 mL glass bottle with 8 mL DMF and 2 mL acetic acid. The mixture solution was fully ultrasound uniform and stirred for several


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minutes after capping the vial. Then the resulted homogeneous solution was put into an oil bath with heating at 140 ºC for 2 h. The finally products were gathered using ethanol at 6,000 rpm centrifugation 10 min and repeated several times. Finally, the PdCu product was dispersed in DMF. A similar procedure was carried out in order to preparation of ternary PdIrCu NCF, just to add 1/5 Pd mole H2IrCl6.хH2O in the mixed solution, then put the oil bath in 140 ℃ for 2 h. 2.3. Preparation of PdCu/C and PdIrCu/C NCF. A typical sythensis process as follows: Ketjenblack (Specific surface area: 1400 m2 g-1) was dispersed in ethanol with 1 mg mL-1 concentration to sonicate for around 30 minutes. The as-prepared PdCu product dispersed in ethanol was sonicated and mixed with the ketjenblack solution. Then the mixed liquid was further ultra-sonicated 1 h and gathered centrifuging using ethanol at 6,000 rpm. The final products were collected by dispersion into ethanol, followed by drying in vacuum at 70 ℃ overnight for using. A similar process was implemented in order to preparation of PdIrCu/C NCF. 2.4. Catalyst Characterization. The morphology of catalysts was characterized by a transmission electron microscopy (TEM, JEOL-JEM 2100) and field emission scanning electron microscopy (FESEM, JSM-6700F). The compositions were assessed by energy-dispersive X-ray detector (EDS, Oxford) and inductively-coupled plasma optical emission spectrometer (ICP-OES, PerkinElmer Optima 8000). The biding energy and crystal structure were obtained by X-ray photoelectron spectroscopy (XPS, VG Thermo ESCALAB 250Xi) and Power X-ray diffraction (P-XRD, XRD-7000), respectively. 2.5. Electrochemical Measurements. Electrochemical datas were obtained by a three-electrode system with electrochemical workstation (CHI760D). The reference electrode was reversible hydrogen electrode (RHE) and Pt foil (1×1 cm2) was used as the counter electrode. The working electrode was obtained by the following procedure: Briefly, the catalyst powder was dispersed into


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isopropanol with 5wt % Nafion solution was sonicated for around 30 min, then 8μL catalyst ink was dripped on a glass electrode (diameter: 4 mm) by pipette and finally natural drying before tested. 2.6. Electrochemically active surface area (ECSA). Considered hydrogen could easily diffuse into bulk metallic Pd3, 26, so we tested and calculated the ECSAs of the catalysts by Cuupd-stripping method27-29. The ECSAs were calculated according to equation (1):3, 30 ECSA=

QCu 420 μC×cm-2 ×m

(1)

where QCu (mC) is the charge calculated from Cu monolayer (Cuupd) region, 420 μC×cm-2 and m is charge density of reduction Cu monolayer and total loading of Pd, respectively. 3. RESULTS AND DISCUSSION

The representative FESEM (Figure S1a) and TEM (Figure S1b) images exhibited that the PdCu products presented nanosheets-constructed flower (NCF) structure, and the average lateral size and thickness is 600 nm and 2.6 nm (insert of Figure S1b), respectively. The HRTEM image (Figure S1c) of a corner of PdCu NCF indicates the lattice distances is 0.22 nm located between face-centered cubic (fcc) Cu (0.20 nm) and Pd (0.23 nm) while it can be indexed to the {111} planar31. FESEM-EDS analysis is shown the atomic percentage contents of Pd and Cu is 48.09% and 51.91%, respectively (Figure S1d). ICP-OES data indicated that the atomic ratio of Pd/Cu is 4.9:5.1, which is basically correspond with the EDS measurement. In addition, the element mapping analysis (Figure S1e-g) is further shown that Pd and Cu are equally distributed on the surface of PdCu NCF. According to previous report that metal Ir possesses unique interface chemical properties and outstanding stability in acid medium owing to its high redox potential32,

33

. Therefore, we

introduced Ir with Cu jointly modify electronic structure of Pd to synthesize Ir-alloyed ultrathin


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Figure 1 The morphology images of PdIrCu NCF (a) FESEM, (b)TEM, (c)HRTEM, insert: the thickness of PdIrCu NCF, (d) further large HRTEM of the red box from (c), (e-h) elemental mapping. ternary PdIrCu NCF structure catalyst. Figure 1a-c exhibits ternary PdIrCu nanocrystal can well maintain the NCF morphology and average size of PdCu. But the thickness of PdIrCu NCF decreased to 1.8 nm from the 2.6 nm of PdCu NCF (insert of Figure 1c), and the spacing of lattice fringe was 0.21 nm from the Figure 1d. In the same way, the EDS (Figure S2) analysis exhibit that the ternary PdIrCu NCF obtained at 140 °C for 2 h with the atomic percentage of Pd, Ir and Cu is 43.47%, 7.54% and 48.99%, respectively. The result is basically consistent with ICP-OES data


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(4.5:0.7:4.8). Furthermore, Pd, Ir and Cu are uniformly distributed over the entire PdIrCu NCF by elemental mapping (Figure 1e-h). In order to better comprehend the establishment process of ternary PdIrCu NCF, experiments study on effect of time were carried out (Figure S3). It canclearly saw the irregular NCF easily obtained when the temperature has just reached 140 °C (Figure S3a), followed by started to wrinkle structure with between the plates each other cross-stacking when the temperature is kept 140 °C for 1 h (Figure S3b), the wrinkling deformation process continue to change and become clearer as well as the NCF morphology has been formed when the heating time was added to 2 h (Figure S3c). Since Ir and Cu were introduced into Pd lattice resulting in lattice contraction, the NCF are distorted forming a ternary PdIrCu NCF with 3D hierarchically structure. When the teating time was contimue built up to 6 h (Figure S3d), the wrinkled NCF was disappear, this may be mainly resulted from the increase in reduction number of Cu2+ in the precursor with extended the reaction time. It is generally known that W(CO)6 is prone to decomposed easily into W and CO at a relatively elevated temperature, the Pd atoms (or seeds) can be obtained by reduce Pd2+ at the beginning of nucleation, resulting in rapid reduction of Pd raw material34. In addition, the CO as a capping agent has a strong adsorption on Pd (111) plane, and effectively hold back continued growth along the crystal orientation, which was promotes the formation of ultrathin wrinkling NCF structure35, 36. When there is absence of W(CO)6 in the reaction system, only closepacked PdIrCu nanoparticles (NPs) can be obtained (Figure S4a). When the mass of W(CO)6 is 20 mg, the flaky structure appears, but it is not very clear (Figure S4b). When the mass of W(CO)6 increased to 50 mg, clearer and regular PdIrCu wrinkled NCF (Figure S4c) can be obtained. When the mass of W(CO)6 continue increased to 100 mg, the NCF was dispersed (Figure S4d). These


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results illustrated that W(CO)6 played an essential role as a capping agent and strong reductant in the formation of ternary PdIrCu NCF. Moreover, we also studied the volume ratio of DMF/acetic acid (DMF/AA) influence on the morphology of PdIrCu NCF. When there is absence of acetic acid in reaction system, the structure of NCF is not obvious (Figure S5a). When the volume ratio of DMF/AA is 9:1, the morphology of NCF is clear, but not very regular (Figure S5b). What is more significant is that when the volume ratio of DMF/AA is 8:2, a clearer and regular wrinkled NCF is obtained (Figure S5c). When the volume ratio of DMF/AA increased to 7:3, the NCF with hierarchical wrinkles gradually dispersed (Figure S5d). When DMF/AA volume ratio is 3:7, NCF can barely be seen or even disappear (Figure S5e). When the solvent is only acetic acid, there is no flaky structure (Figure S5f). To sum up, the optimal reaction conditions for the fabrication of PdIrCu NCF catalyst is 140℃ reaction 2h, W(CO)6 is 50 mg and DMF/AA volume ratio is 8:2.

Figure 2 (a) XRD patterns of Pd-based catalysts, (b) XPS spectra compare of PdCu and PdIrCu NCF in the Pd3d. XRD patterns (Figure 2a) shown the diffraction peaks of Pd-based catalysts corresponding to the Pd (111), (200), (220) and (311) facets with Pd structure of fcc crystal, respectively. Furthermore, the diffraction peaks of both PdCu/C and PdIrCu/C NCF shifted to a higher 2θ angles in comparison to commercial Pd/C, which indicates that the lattice constant is decreased by


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alloying. Calculated from the Bragg formula, the Pd (111) lattice spacing of the PdCu/C and PdIrCu/C NCF is proximately 2.14 Å and 2.10 Å, respectively, which are tally with the observed results of HRTEM measurement value. The XPS spectra of Pd3d both of PdCu/C and PdIrCu/C NCF are deconvoluted into two pairs of doublets (Figure 2b). It is noteworthy that the Pd3d binding energy of PdIrCu/C positively upshift 0.30 eV with respect to that of PdCu/C catalyst, indicating that the lattice strain effect (shortening the bond distance of the Pd-Pd) due to incorporation Ir atoms into PdCu structure. This lattice strain downward shifts the d-band centre of Pd to keep the equal compactedness of d-band and the stability of d-electrons, thus reducing the density of states (DOS) at the corresponding Fermi level. It is not easy to ionize the Pd because of the decreased DOS, this leads to an increase in the binding energies of Pd 3d37. Moreover, the modified electronic structure of Pd as a result of the interaction among Pd, Ir and Cu, at the same time, it also contributes to the positive shift of binding energies23, 27, 38. The electronic effect weakened the adsorption strength for the intermediates of catalystic interface, thereby enhancing the catalytic activity34. The stable cyclic voltammetry (CV) curves of Pd-based catalysts are presented in Figure 3a and Figure S7a. It’s obvious that the areas for Pd oxides formation/reduction and hydrogen adsorption/desorption peaks of PdIrCu/C NCF are larger than the other three Pd-based catalysts, illustrating the existence of more available electrochemically active sites. Combining with the Equation (1) and Figure S6 calculated ECSA of PdIrCu/C NCF is 51.67 m2 gPd-1, which is greater than those of commercial Pd/C (23.65 m2 gPd-1), PdCu/C (45.46 m2 gPd-1) and PdIrCu/C NPs (40.25 m2 gPd-1), the significant increased ECSA of PdCu/C and PdIrCu/C catalysts further indicates the superiority of their unique ultrathin NCF structure. The FAO activity of these Pd-based catalysts were evaluated in N2-saturated0.5 M H2SO4 +


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Figure 3 CV cures of different Pd-based catalysts in N2-saturated (a) 0.5 M H2SO4 solution and (b) 0.5 M H2SO4 + 0.5 M HCOOH solutions, (c) MA and SA values at 0.5 V, (d) Chronopotentiometry curves of Pd-based catalysts at 0.35 V in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solutions. 0.5 M HCOOH solutions at the scan rate of 50 mV s-1. The Figure 3b and S7b present that the current density of 0.4-0.6 V is larger than that of 0.7-0.9 V, thus the electrode of catalysts is via a direct electron transfer route, that is HCOOH

CO2+2H++2e-10, 39-41, whereas the half-wave

potential of PdIrCu/C NCF is negative than commercial Pd/C, PdCu/C and PdIrCu/C NPs, demonstrating it possesses first-class intrinsic electrocatalytic activity. At 0.5 V, Figure 3c and S7c shows that the mass activity (MA, unificated to mass of Pd) of the PdIrCu/C NCF reaches 1.38 A mgPd-1, which is almost 4.31, 1.17 and 1.52-hold than commercial Pd/C (0.32 A mgPd-1), PdCu/C (1.18 A mgPd-1) and PdIrCu/C NPs (0.91 A mgPd-1), respectively. The specific activity (SA, normalized to ECSA) of PdIrCu/C NCF reaches to 2.67 mA cmPd-2, which is almost 1.96, 1.03 and


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1.19 times as many as commercial Pd/C(1.36 mA cmPd-2), PdCu/C (2.59 mA cmPd-2) and PdIrCu/C NPs (2.25 mA cmPd-2), respectively, exhibiting its excellent electrocatalytic activity towards FAO.42, 43 The MA and SA of PdCu/C NCF are 3.69 and 1.90 times bigger than that of commercial Pd/C, symbolling that the introduction of Cu element can chang electronic structure of Pd and increase reaction activity, thus improving the catalytic performance, while the prepared PdCu possesses NCF structure similar to that of PdIrCu to retain the reaction area. PdIrCu/C NPs can also enhance the poisoning tolerance of intermediates such as CO44. It can be explained that the surface chemistry of metal Ir is easily to form Ir-OH species under low potentials, while -OH functional group on Ir surface is able to access COad on Pd surface for further oxidization reaction preventing poisoning from CO23, 24, 45. Performance improvement of the PdIrCu NCF seems to be produced by the joint interaction of Ir and Cu. The MA of the as-prepared catalyzers is also compared and contrasted with published literatures (Table S1), the ultrathin NCF structure and the interaction among of Pd, Ir and Cu increased specific surface area can provide more available active sites. Besides, the 3D structure improve electrical conductivity facilitates the mass transfer process, which are helpful for enhanced FAO activity. Chronoamperometry cures measured in 0.5 M H2SO4 with 0.5 M HCOOH solution at 0.35 V for 6000 s (Figure 3d and S7d). The as-prepared ternary PdIrCu/C NCF electrocatalyst exhibited significance current density decay than commercial Pd/C PdCu/C and PdIrCu/C NPs catalysts in the whole time operation process, suggesting its superior electrocatalytic stability. After 6000 s, the oxidation currents on ternary PdIrCu/C NCF is 104.50 mA mgPd-1，which is almost 9.56, 2.11 and 5.04 times as many as commercial Pd/C (10.93 mA mgPd-1), PdCu/C (49.58 mA mgPd-1) and PdIrCu/C NPs (20.73 mA mgPd-1) catalysts, respectively. This significant difference further validates the robustness of we prepared PdIrCu NCF after long-time tests. As such, the as-obtained PdIrCu NCF with high


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electrocatalytic activity and outstanding stability hold broad application prospects in the actual DFAFCs systems as a high-efficiency electrocatalyst. To further demonstrate the durability of PdIrCu/C NCF catalyst, Chronoamperometry (CP) and CVs were performed for long-term operation as in Figure S8 and S9, respectively. Obviously, the as-prepared PdIrCu/C NCF catalyst exhibits better electrochemical stability than commercial Pd/C, PdCu/C and PdIrCu/C NPs. The peak current density of PdIrCu/C NCF remains about 61.11% after 500 cycles (Figure S9a, b, c and d), which is much superior to commercial Pd/C (only 17.48%), PdCu/C (37.19%) and PdIrCu/C NPs (21.71%). The morphology of PdIrCu/C NCF catalyst after 500 cycles test was examined by FESEM (Figure S10), and no obvious change was observed, further confirming its excellent stability for long-term operation.46

Figure 4 CO-stripping cures (a) and Nyquist plots (b) of the catalysts obtained in 0.5 M H2SO4 + 0.5 M HCOOH solution. As confirmed by the CO-stripping cures (Figure 4a), the negative shift of CO oxidation peak potential is viewed, indicates that the PdIrCu/C NCF possess better CO tolerance capability relative to commercial Pd/C and PdCu/C for FAO47, 48. Nyquist diagram in Figure 4b shows the radius of the impendence loop in the high frequency area, representing the electrical transmission resistance (Rct) of the materials on the electrode. The Rct is close to 242, 132, 60 Ω for commercial


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Pd/C, PdCu/C and PdIrCu/C NCF catalysts, respectively, illustrating that the PdIrCu/C NCF has a lower electron-transfer resistance as a result faster charge transfer rate49,

50

. The standard

exchange current density (i0) is commonly served as one of tools for assessing catalytic activity and a larger i0 demonstrates excellent electrocatalytic activity according to Equation (2):6, 39, 41, 51

i0 =

RT FRct

(2)

where F, R and T is Faradic constant gas constant and absolute temperature, respectively. Combined with Nyquist plots and Equation (2), the calculated i0 to be 4.01×10-5, 7.35×10-5 and 4.28 × 10-4 corresponding to commercial Pd/C, PdCu/C and PdIrCu/C NCF, respectively. illustrating that the PdIrCu/C NCF possesses faster electron transfer rate and much better essential activity.

Figure 5 Schematic illustration of the prepared procedures and enhanced electrocatalytic performance mechanisms of PdIrCu NCF catalyst. Most importantly, the electrocatalysis results clearly and forcefully demonstrated the PdIrCu/C NCF catalyst possesses outstanding electrocatalytic properties towards FAO, such as lower onset potential, higher catalytic performance and better anti-poisoning capability. The prepared procedures and enhanced FAO performance mechanism of PdCu and PdIrCu NCF catalysts are shown in Figure 5. The precursor reactants are reverted to form two-dimensional NCF


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in initially, and then two-dimensional NCF are cross-stacking into 3D NCF. The enhanced electrocatalytic performance of the PdIrCu/C NCF benefit from the following points: 1) the interplay of among Pd, Ir and Cu to change the electronic structure of Pd, besides, metal Ir can dissociate water molecules product -OH group in the low potential, which is benefit for facilitating oxidation of the COad and remove form the active sites of catalysts to reduce the poisoning effect, 2) the ultrathin nanosheets structure of PdIrCu/C increased the specific surface area and provided more available catalytic active sites, 3) the unique 3D NCF structure can enhance the electroconductivity and promote the mass transport process in electrocatalysis reaction. 4. CONCLUSIONS

In conclusion, Ir-alloyed ultrathin ternary PdIrCu/C NCF structure catalyst was successfully prepared by a facile one-step solvothermal reduction without using any surfactant, which exhibits outstanding catalytic activity and durability towards FAO over commercial Pd/C, PdCu/C and PdIrCu/C NPs, this is mainly contributed to the Ir addition for introduced significant antipoisoning ability while modifying electronic structure of Pd for increased reaction active sites and accelerated charge transfer rate as well as facilitated mass transport by ultrathin NCF 3D structure. Consequently, this PdIrCu/C with NCF holds a great promise as anode catalyst for the DFAFCs. ASSOCIATED CONTENT Supporting Information. The morphology of PdCu and PdIrCu NCF, Cuudp-stripping cures and other dates are provided of Pd-based catalysts (PDF). AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] (C.M. Li)


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ORCID: Hong Ming An: 0000-0002-6180-6652 Chang Ming Li: 0000-0002-4041-2574 Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS We gratefully acknowledge to the financial support from Institute for Clean Energy & Advanced Materials, Faculty of Materials and Energy, Southwest University, Chongqing, P.R. China, Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Energies and Chongqing Science and Technology Commission (cstc2012gjhz90002), P.R. China. REFERENCES (1) Steele, B. C. H.; Heinzel, A. Materials for Fuel-Cell Technologies. Nature 2001, 414, 345-352. (2) Chen, W.; Chen, S. W. Oxygen Electroreduction Catalyzed by Gold Nanoclusters: Strong Core Size Effects. Angew. Chem., Int. Ed. 2009, 48, 4386-4389. (3) An, H. M.; Zhao, Z. L.; Wang, Q.; Zhang, L. Y.; Gu, M.; Li, C. M. Ternary PtPdCu Multicubes as a Highly Active and Durable Catalyst toward Oxygen Reduction Reaction. Chemelectrochem 2018, 5, 1345-1349. (4) Zhao, Z. L.; Wang, Q.; Zhang, L. Y.; An, H. M.; Li, Z.; Li, C. M. Galvanic Exchange-Formed Ultra-Low Pt Loading on Synthesized Unique Porous Ag-Pd Nanotubes for Increased Active Sites toward Oxygen Reduction Reaction. Electrochim. Acta 2018, 263, 209-216.


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Ir-Alloyed Ultrathin Ternary PdIrCu Nanosheet-Constructed Flower

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