Materials Science

Metal Bond Strength Regulation Enables Large-scale Synthesis of Intermetallic Nanocrystals for Practical Fuel Cells

Authors

  • Jiashun Liang Huazhong University of Science and Technology ,
  • Yangyang Wan Jiangsu University & California State University Northridge ,
  • Houfu Lv Dalian Institute of Chemical Physics ,
  • Xuan Liu Huazhong University of Science and Technology ,
  • Fan Lv Peking University ,
  • Shenzhou Li Huazhong University of Science and Technology ,
  • Jia Xu Huazhong University of Science and Technology ,
  • Zhi Deng Huazhong University of Science and Technology ,
  • Junyi Liu California State University Northridge ,
  • Siyang Zhang Huazhong University of Science and Technology ,
  • Yingjun Sun Peking University ,
  • Gang Lu California State University Northridge ,
  • Jiantao Han Huazhong University of Science and Technology ,
  • Guoxiong Wang Dalian Institute of Chemical Physics ,
  • Yunhui Huang Huazhong University of Science and Technology ,
  • Shaojun Guo Peking University ,
  • Qing Li Huazhong University of Science and Technology

Abstract

Structurally ordered L10-PtM (M = Fe, Co, Ni, etc) intermetallic nanocrystals (iNCs), benefiting from the chemically ordered structure and higher stability, are one of the best electrocatalysts used for PEMFC. However, their practical development is greatly plagued by the challenge that high-temperature annealing (> 700 °C) has to be used for realizing disorder-order phase transition (DOPT) due to the high activation barrier (Ea), which always leads to severe particle sintering, morphology change, and makes it highly challenging for gram-scale preparation of desirable PtM iNCs. Here, we report a general low-melting-point metal induced bond strength weakening strategy to promote DOPT of PtM (M = Ni, Fe, Cu, Zn) alloy catalysts. We demonstrate that the introduction of Sn can reduce DOPT temperature to a record-low temperature (≤ 450 °C), which enables ten-gram-scale preparation of high-performance L10-PtM iNCs. X-ray spectroscopic studies, in-situ electron microscopy and theoretical calculations reveal that the Sn-facilitated DOPT mechanism at record-low temperature involves the weakened bond strength and reduced Ea via Sn doping, the formation and fast diffusion of low coordinated surface free atom, and subsequent L10 nucleation. Most importantly, the 15% Sn-doped L10-PtNi iNCs display outstanding performance in H2-air fuel cells with a high peak power density of 1.45 W cm-2 for Pt alloy catalysts and less than 25% activity loss after 30000 cycles at a quite low cathode Pt loading amount of 0.12 mg¬Pt cm-2, representing as one of the most efficient cathodic electrocatalyst for PEMFCs.

Content

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