摘要
Oxygen evolution reactions(OERs)as core components of energy conversion and storage technology systems,such as water splitting and rechargeable metal–air batteries,have attracted considerable attention in recent years.Transition metal compounds,particularly layered double hydroxides(LDHs),are considered as the most promising electrocatalysts owing to their unique two-dimensional layer structures and tunable components.However,heir poor intrinsic electrical conductivities and the limited number of active sites hinder their performances.The regulation of the electronic structure is an effective approach to improve the OER activity of LDHs,including cationic and anionic regulation,defect engineering,regulation of intercalated anions,and surface modifications.In this review,we summarize recent advances in the regulation of the electronic structures of LDHs used as electrocatalysts in OERs.In addition,we discuss the effects of each regulation type on OER activities.This review is expected to shed light on the development and design of effective OER electrocatalysts by summarizing various electronic structure regulation pathways and the effects on their catalytic performances.
氢气具有能量密度高、无毒、燃烧产物无环境污染等优点,是一种极具应用前景的可再生能源.目前制氢技术主要包括天然气重整制氢、光解水制氢及电解水制氢,其中天然气重整制氢存在纯度低、成本高的缺点,而光解水制氢技术尚不成熟.电解水制氢纯度高、成本低,已成为一种比较常用且成熟的制氢方法.电解水过程是指在电解池中利用电能分解水分子并释放出氢气和氧气的电化学过程,它包含两个半反应,即阳极析氧反应(OER)和阴极析氢反应(HER).在室温下驱动析氢反应与析氧反应的理论电位分别为0与1.23 V.但是,在实际电解过程中需要额外的电位(过电位)去激活和克服原始反应能垒,因此,尽可能的降低电解水的过电位是氢能广泛应用的必要条件.过渡金属化合物,特别是层状双金属氢氧化物(LDHs),由于其独特的二维层状结构和组成元素可灵活调变等特性,被认为是最具发展前景的电催化剂之一.但LDHs较差的电子导电性和较厚的板层结构极大的限制了其作为氧析出电催化剂的大规模应用.本文总结了LDHs作为OER电催化剂的研究进展,重点介绍了不同阳离子、不同阴离子、缺陷工程、各类插层阴离子和表面改性等改变对材料表面电子结构的影响机制.本文首先介绍了电解水析氧反应在不同电解液中的反应机理,讨论了析氧反应在动力学和热力学过程的主要障碍.通过对大量文献的归纳,综述了近年来通过调控LDHs的电子结构增加其活性位点数目、增强活性位点的本征活性,进而提高其OER催化性能的研究成果和最新进展,重点探讨了阳离子调控、阴离子调控、缺陷工程、插层阴离子调控和表面改性等调控方式对LDHs电催化剂OER性能的影响,总结了各种电子结构调控及其对电催化性能的影响.通过分析不同价态阳离子、阴离子对催化活性位点的电子结构影响,不同层间插层阴离子对催化剂层间距的影响,不同类型缺陷带来的微观结构和表层电子结构变化及表面改性带来的表层电子状态,亲疏水性的区别等实验现象,总结了层状过渡金属氢氧化物OER性能提升的策略.此外,本文还做了在LDHs的催化性能调控方面的挑战和展望,对未来开发和设计高效的OER电催化剂提供了崭新的思路.
基金
国家自然科学基金(51402100,21573066,21825201)
