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ABSTRACT Hydrogen production through water electrolysis powered by renewable sources, particularly via proton exchange membrane water electrolysis (PEMWE), has garnered considerable interest due to its high efficiency and operational flexibility. However, the widespread adoption of this technology is primarily hindered by the intrinsically sluggish and complex reaction kinetics of the anodic acidic oxygen evolution reaction (OER). Contemporary research on high‐performance catalysts, including noble metal oxides and transition metal oxides, predominantly adopts a thermodynamic perspective, optimizing catalytic performance by modulating the adsorption energies of key reaction intermediates. However, this mainstream strategy frequently fails to adequately consider the actual electrochemical reaction environment, that is, the structured electric double layer at the electrode/electrolyte interface. The essence of electrocatalysis resides at the electrode–electrolyte interface, where the structure, orientation, and hydrogen‐bond network of interfacial water molecules critically influence water adsorption and activation, proton transfer, intermediate stabilization, and reaction pathway selection, thereby governing the overall reaction kinetics. This review focuses on acidic OER and systematically examines the central role of interfacial water throughout the catalytic process. We first clarify its function in different mechanistic pathways and introduce relevant in situ characterization techniques. Subsequently, we delve into the multiple roles of interfacial water, detailing its functions in participating as a reactant, stabilizing key intermediates, and regulating mass transport. Finally, we summarize recent strategies and design principles for enhancing catalyst performance through interfacial water structure engineering. This review delineates and consolidates the critical role of interfacial water structure, offering a new perspective for the rational design of efficient and stable acidic OER catalysts.
Wu et al. (Sun,) studied this question.