用于H2电化学氧化的Ni基纳米催化剂研究

Alkaline fuel cell (AFC) is a kind of green power with high efficiency and cleanness. Especially, with the development of the alkaline anion exchange membrane technology, the carbonation of electrolyte has been avoided, which makes AFC more competitive. However, Pt-based noble metals used as anode catalyst are few and expensive. For non-noble metal catalysts, the hydrogen oxidation (HOR) activities and stability are influenced by many factors, such as metal elementary composition, size and properties of carriers, resulting in the complex catalytic mechanisms. Now their catalytic mechanisms are still very unclear, which restricts the further commercial exploitation of the catalysts. In this project, by a combination of quantum chemistry calculations and experimental methods, we will systematically study the competitive mechanisms of HOR and surface oxidation of graphene supported Ni-based non-noble metal nano-catalysts, analyze the influences of catalyst oxophilicity, pH values, cations, and interface water on reaction mechanisms, and investigate the effects of alloying, size, and carriers on the HOR activities and oxidation resistance of catalysts. The relationship between catalyst structures and HOR activities as well as oxidation resistance will be founded, and some catalyst systems with high HOR activity and oxidation resistance in alkaline medium will be prepared and screened out. These results will provide reference and guidance for design of non-noble metal electrocatalysts with high HOR activity and oxidation resistance in alkaline medium.

碱性燃料电池（AFC）是一种高效洁净的绿色电源。尤其是近年来碱性阴离子交换膜技术的发展，避免了电解质碳酸化的问题，使AFC更具有竞争力。但是，AFC使用的Pt基贵金属阳极催化剂储量稀少、价格昂贵。非贵金属催化剂的H2氧化（HOR）活性和稳定性受组成、尺寸和载体性质等多种因素影响，作用机理复杂且尚不明确，极大限制了该类催化剂的商业化开发。本课题拟采用量子化学与实验相结合的方法从电子层次上研究石墨烯负载型Ni基非贵金属纳米催化剂的表面氧化和HOR竞争机理，分析催化剂亲氧性、pH值、阳离子、界面水等因素对反应机理的影响，考察催化剂合金效应、尺寸效应和载体协同效应对催化剂抗氧化性和HOR活性的影响。建立起催化剂结构与抗氧化性和HOR活性之间的构效关系，制备和筛选出若干适用于碱性介质的高HOR活性和高稳定性Ni基催化剂体系。为适用于碱性介质的高活性、高稳定性非贵金属HOR电催化剂设计提供借鉴与指导。

基于非贵金属电催化剂的碱性燃料电池（AFC）是一种清洁、高效、低成本的绿色电源。但AFC阳极的氢氧化反应（HOR）动力学相对于阴极非常缓慢，导致阳极更高的催化剂负载量和成本。针对这一问题，国内外学者主要集中在Ni基非贵金属催化剂的研究与开发。目前Ni基催化剂的活性和抗氧化性仍较差，催化机理复杂且尚不明确，催化剂的制备大多是经验性的尝试研究，缺乏有效的理论指导，极大限制了此类催化剂的进一步优化设计。本课题首先采用第一性原理方法从电子层次上系统研究了Pt以及Ni、NiNP/G、NiNP/B-G、NiNP/N-G、NiM、MSAC/G (M = V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Pt)等Ni基催化剂的碱性HOR机理和抗氧化性能。研究发现Pt和Ni基催化剂的HOR过程主要遵循Tafel−Volmer机理。催化剂的HOR活性主要由氢的吸附控制，氢吸附自由能可作为催化剂碱性HOR活性的描述符（最佳值0.414 eV）。催化剂的亲氧性对抗氧化性有重要影响，氧化势可作为催化剂电化学稳定性的描述符。合金效应、石墨烯载体效应、B/N掺杂可对催化剂的HOR活性起到协同催化增强作用。基于理论研究结果，进一步制备出了具有优异HOR活性和抗氧化性的Ni/N-rGO、NiW、NiW/rGO、NiMoW、Ni3N/Ni/N-GFs等Ni基非贵金属催化剂。建立了催化剂结构设计→氢吸附自由能/氧化势计算→HOR活性/稳定性分析→催化剂制备的碱性燃料电池阳极材料开发技术路线。通过本项目的研究，使人们对于AFC阳极HOR机理有了更深一步的认识，对高性能非贵金属HOR催化剂的设计开发具有一定的指导意义。