摘要
An efficient and economical oxygen evolution reaction(OER)catalyst is critical to the widespread application of solar energy to fuel conversion.Among many potential OER catalysts,the metal oxyhydroxides,especially FeOOH,show promising OER reactivity.In the present work,we performed a DFT+U study of the OER mechanism on theγ‐FeOOH(010)surface.In particular,we established the chemical potential of the OH?and hole pair and included the OH?anion in the reaction pathway,accounting to the alkaline conditions of anodic OER process.We then analyzed the OER pathways on the surface with OH‐,O‐and Fe‐terminations.On the surface with OH‐and O‐terminations,the O2molecule could form from either OH reacting with the surface oxygen species(-OH*and-O*)or the combination of two surface oxygen species.On the Fe‐terminated surface,O2can only form by adsorbing OH on the Fe sites first.The potential‐limiting step of the oxygen evolution with different surface terminations was determined by following the free‐energy change of the elementary steps along each pathway.Our results show that oxygen formation requires recreating the surface Fe sites,and consequently,the condition that favors the partially exposed Fe sites will promote oxygen formation.
一个高效经济的氧析出反应(OER)催化剂是大范围应用太阳能转化能源的关键.在众多有潜力的OER催化剂中,金属氢氧化物,尤其是Fe OOH表现出很高的OER活性.我们采用DFT+U研究了γ-Fe OOH(010)表面上OER反应机理;得到了OH–和空穴对的化学势,并将OH–阴离子包含在反应机理中,以此来说明碱性条件下阳极的OER过程.随后分析了催化剂中OH-,O-和Fe-终止的表面上OER反应路径.含有OH-,O-终止的表面上,O_2分子是通过OH与表面氧物种(–OH*和–O*)反应,或二个表面氧物种相结合而形成的.在Fe-终止的表面上,O_2只能通过首先在Fe位上吸附OH而形成.不同形式表面上O_2析出的化学势决定步骤取决于每个路径中基元步骤自由能的变化.结果表明,O_2的形成需要重建表面Fe位,因此,有利于部分暴露Fe位的条件也将促进O_2的形成.
基金
supported by the Chemical,Biological,Environmental,and Transport Systems(CBET)program of US National Science Foundation(CBET-1438440)~~
