High-entropy oxides as promising electrocatalysts for oxygen evolution reaction: A review

It is acknowledged that the oxygen evolution reaction (OER) becomes a significant challenge owing to tetra-electronic transfer process. High-entropy oxides (HEOs) have attracted significant interest due to their abundant active sites, large specific surface area, and excellent electrochemical properties. However, understanding the relationship between the structural properties and electrochemical performance of HEOs remains challenging. Therefore, we comprehensively review the fundamental principles of OER, with particular emphasis on recent advancements in Joule-heating and carbothermal shock techniques for synthesizing HEOs. Furthermore, we compare the effects of rock salt, spinel, and perovskite crystal structures of HEOs on OER performance whereas perovskite HEOs superior the other crystal structures in terms of the design of the conformational entropy as well as the performance of OERs. In contrast to previous reviews on HEOs, we reveal potential factors for catalytic activity enhancement in HEOs materials, including high-valent cation doping, high-entropy engineering-induced lattice distortion, modulation of oxygen vacancies, and theoretical calculations for an in-depth resolution of electronic structure and activity. This study provides new insights and a solid theoretical foundation for the design of high-performance HEOs electrocatalysts.