Advances in anion vacancy for electrocatalytic oxygen evolution reaction

Electrocatalytic oxygen evolution reaction (OER), as a central process of many important energy conversion devices, is a very dynamic process. Understanding the characteristics of the materials that affect OER performance is of vital significance for the development of more advanced OER electrocatalysts. Anion vacancy engineering, with the functions of improving the intrinsic activity, exposing more accessible surface active sites, improving electrical conductivity and mechanical stability, plays an extra role in enhancing the electrocatalytic OER performance of transition metal compounds. Although the great endeavors made, the intrinsic reaction mechanism and dynamic behavior of anion vacancy sites are still unclear. Therefore, studying the structure–activity relationship of defective electrocatalysts is favorable for gaining a better understanding on the specific reaction mechanism and dynamic behavior. Herein, in this review, a systematic overview of the effect of anion vacancies, such as oxygen, sulfur, phosphorous, selenium vacancies on electrocatalytic OER performance of transition metal compounds is summarized, along with some advanced synthetic strategies and characterizations. Moreover, the challenges and future directions of anion vacancies engineering toward OER are also briefly discussed.