Supporting Information. Unique Core-Shell Concave Octahedron with Enhanced Methanol Oxidation Activity

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1 Supporting Information Unique Core-Shell Concave Octahedron with Enhanced Methanol Oxidation Activity Qi Wang a, Zhiliang Zhao c, Yanlin Jia* b, Mingpu Wang a, Weihong Qi a, Yong Pang a, Jiang Yi a, Yufang Zhang a, Zhou Li a, Zhuo Zhang d a. School of Materials Science and Engineering, Central South University, Changsha, , P. R. China b. School of Materials Science and Engineering, Beijing University of Technology, Beijing, , P.R. China c. Institute for Clean Energy & Advanced Materials, Faculty of Materials and Energy, Southwest University, Chongqing , P. R. China. d. Advanced Research Center, Central South University, Changsha, , P. R. China * Corresponding authors: jiayanlin@126.com (Yanlin Jia) KEYWORDS: Core-shell, High-index, CuPt, Concave octahedron, Methanol oxidation reaction S-1

2 Table of contents: Synthesis of CuPt octahedron Figure S1: Magnified SEM and TEM images. Figure S2: Atomic model of high index surfaces. Figure S3: HRTEM images of core and shell and corresponding FFT. Figure S4: Color change overall the reaction process. Figure S5: Geometry model of rhombic dodecahedron. Figure S6: TEM images of T21/2-25/2 and T25/4. Figure S7: TEM images of T21/2 and T25/2, and corresponding EDS results. Figure S8: TEM images of T15.5/2-25/2 and corresponding CV curves. Figure S9: XRD, XPS comparison of T17/2-25/2, T21/2-25/2 and T25/4. Table S1: Composition of samples determined by ICP-AES, EDS and XPS Figure S10: HADDF-STEM image of catalyst. Figure S11: CV profiles of catalyst dealloying process. Figure S12: TEM images and XRD pattern of octahedral CuPt nanocrystals Figure S13: CV profiles of and commercial before and after 1000 cycles. Figure S14: Morphology observation of catalyst and commercial Pt/C before and after cycling. Table S2: Summary of typical reported CuPt catalysis for MOR Reference S-2

3 Additional experimental procedure Synthesis of CuPt nanooctahedron In a typical procedure, 14 mg of Cu(acac) 2, 20 mg of Pt(acac) 2 and 1 ml OAm were added in 9 ml N,N-Dimethylformamide (DMF) solution. The mixture was magnetically stirred at 40 for 30 min. After that, the resulting solution was heated in a Teflon-lined stainless steel autoclave at 180 for 12 h and then cooled down to room temperature. The obtained sample was then loaded on Vulcan XC-72 carbon. S-3

4 Figure S1 Magnified SEM (A) and TEM (B) image illustrates the uniformity of as-prepared concave octahedron particles S-4

5 Figure S3 (A) HRTEM including core and leg of a concave octahedron particle. (B) lattice fringe and (D) corresponding FFT of core, the d-spacing was measured to be 2.10 Å. (C) lattice fringe and (E) corresponding FFT of core, the d-spacing was measured to be 2.19 Å. It is obvious that the core and shell have the same orientation. The overlap of (D) and (E) show the indistinguishable nature of core and shell through SEAD. Figure S4 color of different reaction stages reflecting the revolution of products. From brilliant yellow to orange, green and finally dark. S-5

6 Figure S5 Geometry model of rhombic dodecahedron. It is encapsulated by twelve (110) surface, any preferable deposition of shell in the preferential deposit site may lead to higher index S-6

7 Figure S6 TEM images of the nanoparticles synthesized by different initial temperature. (A) and (B) images of sample T21/2-25/2. (C) and (D) images of sample T25/4. As seen in (A-B), no obvious morphology change was spotted in T21/2-25/2 except for decreased size compared to T17/2-25/2. However, when initial temperature raised to 250, some sphere particles were found (C-D). S-7

8 Figure S7 (A) TEM image of sample collected at 2 hours after reacted at an initial 210 (T21/2). (B) TEM-EDS of T21/2 and T21/2-25/2, revealing majority of Pt atoms have deposit after 2 hours at 210. (C) TEM image of sample collected at 2 hours after reacted at an initial 250. (D) TEM-EDS of T25/2 and T25/4. S-8

9 Figure S8 (A) TEM images of samples obtained under an initial temperature of 155. (B) corresponding distribution histogram of nanoparticles. (C) CV profiles of the catalysts recorded in N 2 -saturated 0.5 M H 2 SO 4 solution at a sweep rate of 50 mv s -1 and (D) CV profiles of mass activities of T15.5/2-25/2 catalysts for MOR in 0.5 M H 2 SO M CH 3 OH solutions. These particles still present concave octahedron morphology, but the size ranges from nm in this initial temperature. The reason can be attributed to uneven Cu seeds. The ECSAs (12.2 m 2 g -1 ) and mass activity (277 A g -1 Pt) are also poor due to the large size. S-9

10 Figure S9 (A) XRD patterns of T17/2-25/2, T21/2-25/2 and T25/4. (B) magnification of black box in (A), revealing up-shift of (111) peak of CuPt alloy. (C) XPS spectra of T17/2-25/2, T21/2-25/2 and T25/4, demonstrating surface Cu/Pt molar ratio of these samples. (D) High-resolution XPS patterns of the Pt 4f. Table S1 Compositions (Cu/Pt molar ratios) of different samples determined by EDS, ICP and XPS. Cu/Pt ICP-AES EDS XPS sample before after T17/2-25/2 71.9/ / / :39.9 T21/2-25/2 75.1/ / / :42.3 T25/4 70.1/ / / :44.9 S-10

11 Figure S10 HAADF STEM image of after loaded on Vulcant-72 carbon. Figure S11 CV profiles of catalyst during electrochemical dealloying process. The broad hydrogen-adsorption/desorption regime and redox-peak couple of Pt oxide become clear by gradual removal of Cu atom. Stable CV curve was obtained after 3 cycles, facilitating the identification of low Cu content surface. S-11

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13 Figure S13 Voltammetry curves for (A) commercial Pt/C catalyst and (C) T17/2-25/2 catalyst before and after the accelerated stability tests. sweep rate, 100 mv s -1. And electrocatalytic stability test of (B) commercial Pt/C catalyst and (D) T17/2-25/2 Cu@CuPt/C catalyst before and after 1000 cycles of accelerated stability tests. sweep rate, 50 mv s -1. Normalized to the loading amount of Pt. S-13

14 Figure S14 TEM images of commercial Pt/C catalyst (A-B) and catalyst (C-F) before (C) and after 1000 cycles (D-F). No obvious aggregation was spotted in catalyst. In contrast, commercial Pt/C catalyst suffer serious aggregation after 1000 cycles. (E) magnified TEM images disclosing gradual miss of Cu-rich core. (F) HRTEM of legs revealing the invariability of CuPt shell. S-14

15 Table S2: Summary of typical reported CuPt catalysis for MOR Catalyst Electrolyte Mass activity/a mg-1 Specific activity/ma cm-2 Ref Pt Cu alloy concave nanocubes 0.1 M HClO PtCu hexapod 0.5 M H2SO hollow-ptcu 0.5 M H2SO Nanoporous Pt Cu Microwires rhombic dodecahedral PtCu nanoframes 0.5 M H2SO M HClO Pt Cu hollow 0.5 M H2SO Pt-Cu nanoparticles 0.5 M H2SO porous PtCu 0.1 M HClO PtCu Nanowire 0.5 M H2SO Hierarchical Branched Pt-Cu 0.5 M H2SO concave octahedron Cu@CuPt 0.5 M H2SO this work S-15

16 Reference 1.Qi, Y.; Bian, T.; Choi, S.-I.; Jiang, Y.; Jin, C.; Fu, M.; Zhang, H.; Yang, D., Kinetically Controlled Synthesis of Pt Cu Alloy Concave Nanocubes with High-Index Facets for Methanol Electro-oxidation. Chem. Commun. 2014, 50 (5), Wang, K.; Sriphathoorat, R.; Luo, S.; Tang, M.; Du, H.; Shen, P. K., Ultrathin PtCu Hexapod Nanocrystals with Enhanced Catalytic Performance for Electro-oxidation Reactions. J. Mater. Chem. A 2016, 4 (35), Huang, X.; Chen, Y.; Zhu, E.; Xu, Y.; Duan, X.; Huang, Y., Monodisperse Cu@ PtCu Nanocrystals and Their Conversion into Hollow-PtCu Nanostructures for Methanol Oxidation. J. Mater. Chem. A 2013, 1 (46), Qiu, H.-J.; Shen, X.; Wang, J.; Hirata, A.; Fujita, T.; Wang, Y.; Chen, M., Aligned Nanoporous Pt Cu Bimetallic Microwires with High Catalytic Activity toward Methanol Electrooxidation. ACS Catal. 2015, 5 (6), Ding, J.; Zhu, X.; Bu, L.; Yao, J.; Guo, J.; Guo, S.; Huang, X., Highly Open Rhombic Dodecahedral PtCu Nanoframes. Chem. Commun. 2015, 51 (47), Yu, X.; Wang, D.; Peng, Q.; Li, Y., High Performance Electrocatalyst Pt Cu Hollow Nanocrystals. Chem. Commun. 2011, 47 (28), Du, X.; Luo, S.; Du, H.; Tang, M.; Huang, X.; Shen, P. K., Monodisperse and Self-Assembled Pt-Cu Nanoparticles as An Efficient Electrocatalyst for The Methanol Oxidation Reaction. J. Mater. Chem. A 2016, 4 (5), Eid, K.; Wang, H.; He, P.; Wang, K.; Ahamad, T.; Alshehri, S. M.; Yamauchi, Y.; Wang, L., One-Step Synthesis of Porous Bimetallic PtCu Nanocrystals with High Electrocatalytic Activity for Methanol Oxidation Reaction. Nanoscale 2015, 7 (40), Xiao, M.; Li, S.; Zhao, X.; Zhu, J.; Yin, M.; Liu, C.; Xing, W., Enhanced Catalytic Performance of Composition Tunable PtCu Nanowire Networks for Methanol Electrooxidation. Chemcatchem 2014, 6 (10), Cao, Y.; Yang, Y.; Shan, Y.; Huang, Z., One-Pot and Facile Fabrication of Hierarchical Branched Pt Cu Nanoparticles as Excellent Electrocatalysts for Direct Methanol Fuel Cells. ACS Appl. Mater. Interfaces 2016, 8 (9), S-16