Advanced electrocatalysts with unusual active sites for electrochemical water splitting

Electrochemical water splitting represents a promising technology for green hydrogen production. To design advanced electrocatalysts, it is crucial to identify their active sites and interpret the relationship between their structures and performance. Materials extensively studied as electrocatalysts include noble-metal-based (e.g., Ru, Ir, and Pt) and non-noble-metal-based (e.g., 3d transition metals) compounds. Recently, advancements in characterization techniques and theoretical calculations have revealed novel and unusual active sites. The present review highlights the latest achievements in the discovery and identification of various unconventional active sites for electrochemical water splitting, with a focus on state-of-the-art strategies for determining true active sites and establishing structure–activity relationships. Furthermore, we discuss the remaining challenges and future perspectives for the development of next-generation electrocatalysts with unusual active sites. By presenting a fresh perspective on the unconventional reaction sites involved in electrochemical water splitting, this review aims to provide valuable guidance for the future study of electrocatalysts in industrial applications.