电子效应对非贵双金属电催化剂的氢气氧化反应的作用机理

Heavy reliance on the Pt-based electrocatalysts for both hydrogen oxidation and oxygen reduction reactions prohibits the large scale commercialization of H2-O2 proton exchange membrane fuel cells. As an alternative, anion exchange membrane fuel cells (AEMFC) are more economically viable owing to the availability of much cheaper membranes and non-precious metal electrocatalysts for both anode and cathode. While some non-Pt group metal catalysts have shown comparable oxygen reduction reaction activities to the Pt-based electrocatalysts, the options for the anodic hydrogen oxidation reaction (HOR) are limited to Pt-group metals. The reaction mechanism on non-precious metals in base remains inconclusive. In this proposed project, we aim at identifying the reaction mechanism and reaction descriptors on selected bimetallic model electrocatalysts for the HOR in base, which are crucial to the design and development of non-precious metal electrocatalysts for AEMFC..We propose to investigate Ni-based and Cu-based bimetallic model electrocatalysts with controlled compositions and structures. In situ X-ray absorption spectroscopy will be used to measure the d-band vacancy and electronic structure change with different H and OH coverage at different potentials. DFT calculations will be performed to assist identifying possible active sites, adsorption energies and reaction pathways. Both experimental and calculated results will be correlated to the HOR activity and stability. We will identify the HOR mechanism and reaction descriptors on these non-precious bimetallic electrocatalysts. Upon the completion of the proposed research, we expect to provide a solid understanding on the HOR in base, and establish a structure – performance relationship as guidance for rational catalyst design.

质子膜燃料电池高度依赖Pt基贵金属催化剂，限制了它的大规模商业化应用，而碱性膜燃料电池因其价格优势而更具备竞争力。但碱性环境下氢气氧化反应（HOR）最好的催化剂仍局限在Pt族贵金属催化剂，并且碱性环境下的HOR反应机理尚无定论。本项目将针对这一关键课题展开研究，明确碱性环境下的HOR反应机理及控制反应速率的关键因素（描述因子），这对于碱性膜燃料电池的非贵金属催化剂的设计与开发十分关键。. 本项目将以组分结构可控的Ni基Cu基双金属模型催化剂为研究对象，利用在线 X 射线吸收光谱研究双金属体系的表面电子结构以及不同电位下不同的H和OH覆盖度对其影响，结合DFT理论计算协助考察不同反应位点、吸附能以及可能的反应路径，以此确定反应机理，揭示控制反应速率的关键因素，建立催化剂的构效关系，为碱性环境下高效HOR催化剂的设计与开发提供理论基础和实验依据。

质子膜燃料电池高度依赖Pt-基贵金属催化剂，大大限制了它的大规模商业化应用。而碱性膜燃料电池因其价格优势而更具备竞争力。尽管碱性环境下Ni基非贵金属显示出一定的电催化氢氧化活性，但其性能仍远小于Pt族贵金属催化剂，并且，其在碱性环境下的氢气氧化反应机理尚无定论。本项目负责人及参与的研究人员就项目所提出的科学问题开展了相关的研究，在该项目经费的支持下，通过采购一些小型仪器设备，完善了电化学测试平台的搭建；通过对Ni基二元合金的系统研究，明确碱性环境下的氢气氧化反应机理及控制反应速率的关键因素（描述因子），这对于碱性膜燃料电池的非贵金属催化剂的设计与开发十分关键。目前所取得的成果总结如下：.（1）: Ni基二元合金HOR性能为NiMo＞NiW＞NiMn，其失活电位为NiMo<NiMn<NiW，这是由于Ni金属与第二种金属进行合金化过程调控了金属Ni的d电子能带中心，进而影响了催化剂对氢的结合能以及对含氧物质的结合能。由此得出Ni基材料表面对氢和含氧物质的结合能对其HOR活性和稳定性有重要影响。（2）: Ni催化剂中的晶格氧含量与HOR活性密切相关。随着催化剂中晶格氧含量增加，Ni与氢原子之间结合能会减弱。适当含量晶格氧存在下Ni电子结构得以调控，其对H的吸附能为最优，加快了HOR过程中的Volmer步骤。这些成果揭示了掺杂第二金属或者调控晶格氧在促进碱性电解质中HOR动力学方面的重要作用，为高效催化剂的合理设计与开发提供理论基础与实验依据。.到目前为止，依托本项目已发表论文两篇，另有三篇正在撰写和投稿中，一项专利正在申请中。