Abstract: The electrochemical oxygen evolution reaction (OER) plays an important role in many clean electrochemical energy storage and conversion systems, such as electrochemical water splitting, rechargeable metal-air batteries, and electrochemical CO₂ reduction. However, the OER involves a complex four-electron process and suffers from intrinsically sluggish kinetics, which greatly impairs the efficiency of electrochemical systems. In addition, state-of-the-art RuO₂-based OER electrocatalysts are too expensive and scarce for practical applications. The development of highly active, cost-effective, and durable electrocatalysts that can improve OER performance (activity and durability) is of significant importance in realizing the widespread application of these advanced technologies. To date, considerable progress has been made in the development of alternative, noble metal-free OER electrocatalysts. Among these alternative catalysts, transition metal compounds have received particular attention and have shown activities comparable to or even higher than those of their precious metal counterparts. In contrast to many other electrocatalysts, such as carbon-based materials, transition metal compounds often exhibit a surface reconstruction phenomenon that is accompanied by the transformation of valence states during electrochemical OER processes. This surface reconstruction results in changes to the true active sites and an improvement or reduction in OER catalytic performance. Therefore, understanding the self-reconstruction process and precisely identifying the true active sites on electrocatalyst surfaces will help us to finely tune the properties and activities of OER catalysts. This review provides a comprehensive summary of recent progress made in understanding the surface reconstruction phenomena of various transition metal-based OER electrocatalysts, focusing on uncovering the correlations among structure, surface reconstruction and intrinsic activity. Recent advances in OER electrocatalysts that exhibit a surface self-reconstruction capability are also discussed. We identify possible challenges and perspectives for the development of OER electrocatalysts based on surface reconstruction. We hope this review will provide readers with some guidance on the rational design of catalysts for various electrochemical reactions.

Key words: Oxygen evolution reaction (OER), Surface reconstruction, Electrocatalyst, Metal oxides, In situ/Operando characterization