Regulation Strategy of Transition Metal Oxide-Based Electrocatalysts for Enhanced Oxygen Evolution Reaction

ConspectusThe deployment of hydrogen as alternative energy carrier is a promising route to reduce the consumption of fossil fuel and achieve the "zero carbon" target. Water electrolysis, powered by renewable energy sources, is regarded as the most environmentally friendly and efficient technology for hydrogen production. Generally, the sluggish oxygen evolution reaction (OER) process at the anode predominantly limits the efficiency of water electrolysis. Therefore, developing highly efficient electrocatalysts to accelerate the OER kinetic process has always been a crucial and hot topic. Recently, transition metal oxide (TMO)-based materials have attracted much attention as OER electrocatalysts because of their facile fabrication, low cost, and synergistic effects between the coupled metals. However, further enhancement of the catalytic performance of TMO encounters a bottleneck originated from the limited regulation strategies.Typically, regulation strategies of metal oxide-based electrocatalysts could be classified into three different levels. (1) For the bulk TMO electrocatalyst, reducing the particle size would generate more catalytically active sites, which is usually adopted as the basic method to enhance the overall catalytic activities. However, simple reduction in the particle size demonstrated limited promotion of the catalytic performance, because the intrinsic activity of individual sites is still very low. (2) To further enhance the catalytic activity of TMO, mesoscale modulation strategies are proposed, which usually involve the optimization of interfaces where the active sites are embedded in, including surface reconstruction, constructing heterostructure, and phase engineering. (3) In addition to the interface modulation, more remarkable regulation strategies focus on enhancing the catalytic performance at the atomic level, such as heteroatom doping, defect engineering, and so on. In addition to the modulation of electrocatalysts themselves, recent advances demonstrated that external field effects can also manipulate the catalytic property of TMO-based electrocatalysts by coupling the field with the active sites. All these strategies would afford considerable opportunities on fundamental investigation and practical applications of TMO-based electrocatalysts.In this Account, we highlighted recent progress of the regulation strategies for TMO-based electrocatalysts. We started with the introduction of two different basic mechanisms of OER process. Then we conducted an in-depth discussion about the regulation strategies used to enhance the OER activities of TMO-based electrocatalysts, including defect engineering, surface reconstruction, phase engineering, interface engineering, and application of an external field. We end the Account with a summary of current challenges for TMO-based electrocatalysts for OER and point out some possible opportunities for the future designing of highly efficient TMO-based electrocatalysts.