金属氧化物电催化析氧机理的研究进展

Research Progress in Oxygen Evolution Reaction Mechanism of Metal Oxides

电解水制氢是风能、潮汐能、太阳能等可再生能源转换和存储的重要途径。受限于四电子缓慢动力学过程,析氧反应(Oxygen evolution reaction,OER)是水分解的瓶颈反应。高活性析氧电催化剂是实现高效电解水制氢的关键之一。自从20世纪电解水发展以来,金属氧化物由于具有较好的活性和稳定性,是研究最深入也是最有发展前景的一类低成本析氧电催化剂。对催化反应机理的认识是高效析氧电催化剂理性设计的前提和关键,开发高效稳定的析氧催化剂并阐明其反应机理是目前析氧电催化领域的热点课题。按照一般异相催化的机理范式,人们提出了传统吸附机理,并建立了相应的活性预测模型来指导催化剂的研究。然而随着研究的深入,基于传统催化机理的活性预测模型和描述符的局限性日趋显现,部分新型催化剂的高活性和动力学特征无法用传统机理模型进行解释,析氧催化剂的研究也由此遭遇瓶颈。近年来,得益于各种先进表征手段和理论计算的飞速发展,新型析氧电催化机理逐渐被发展,为下一代高性能电催化剂的指明了方向。目前提出的新型催化机理主要有:晶格氧机理、双位点协同耦联机理、质子受体机理。同时,近期在一些催化剂中影响催化剂稳定性的阳离子析出机理也得以阐明。本文从梳理金属氧化物催化剂的结构和传统催化机理出发,对目前四种新型电催化机理——晶格氧机理、双位点协同耦联机理、质子受体机理和阳离子析出机理,进行了系统性分析,并对理论计算辅助的析氧机理研究以及电催化活性描述符进行了总结,最后对当前析氧电催化机理研究中存在的问题以及可能的解决方案进行了展望。本文期望可为相关领域的研究工作提供参考,从而有效推动下一代高性能析氧电催化剂的发展。

Water splitting is essential for the conversion and storage of renewable energy such as wind,tidal,and solar energy.Oxygen evolution reac-tion(OER)is the bottleneck of water splitting,due to the sluggish four-electron transfer process.An efficient and durable electrocatalyst isrequired to improve the overall efficiency of electrolysis.Metal oxides have been widely investigated in the past few decades,and are consideredas the most promising OER electrocatalyst,given the low cost and moderate performance.The rational design of efficient catalysts firstly calls for a better understanding of the OER mechanism.Much efforthas been devoted to providinginsights to elucidate the detailed mechanism.The traditional adsorption-desorption model was learned from heterogeneous catalysis and worked tosearch for descriptors,which guides the fast screen of advanced electrocatalysts.More recently,the traditional mechanism has been progressive-l y challenged.The high activity and kinetics of some new electrocatalysts can not be fully explained or even contradict the traditional mechanism,which in turn preclude the exploration of novel electrocatalysts.Thanks to the development of advanced characterization techniques and theoretical calculation methods in recent years,the understanding of the OER mechanism has been pushed forwards well.New catalytic mechanisms have been proposed and validated,which sheds light on the rational design of advanced electrocatalysts.These new mechanisms include:lattice oxygen evolution mechanism(LOM),dual-sites mechanism with O-O bond coupling,proton acceptor mechanism.In addition,the mechanism of cation dissolution has also been elucidated in some cases to explain the stability of the catalysts.In this review,we start with the introduction of metal oxides and the traditional OER mechanisms.Following this,we systematically summarize the newly proposed mechanisms of lattice oxygen evolution mechanism(LOM),dual-sites mechanism with O-O bond coupling,proton acceptor mechanism,and cation dissolution mechanism.The representative researches on theoretical calculation and descriptors are highlighted.In the end,present challenges are discussed and suggestions that are potentially interesting for future studies are provided for the hotly developed field.We hope the review will become an important tutorial for the field,pushing forwards the fast exploration of advanced OER electrocatalysts.