Interfacial Water Configurations: Evolution and Implications for Electrocatalysis.

Water plays a pivotal role in electrocatalysis, extending far beyond its function as a solvent to govern proton-coupled electron transfer and interfacial mass transport. The high O─H bond energy, however, renders water dissociation a major kinetic bottleneck in many electrocatalytic reactions. The configurational details of the interfacial water layer on catalyst surfaces, particularly molecular orientation and hydrogen-bonding networks within the electrical double layer under applied bias, govern the electrochemical performance of electrode materials. In catalytic processes, they facilitate the transport of protons, electrons, and other reactive species among diverse active sites and ultimately enhance reaction kinetics. Despite the significant impact of interfacial water, deciphering its configurations and translating this understanding into rational control over catalytic processes remains elusive. This review addresses this critical challenge by providing a comprehensive and mechanistic understanding of how interfacial water structures govern reaction pathways. We aim to bridge the gap between unraveling the intricate role of water structures and establishing robust design principles for advanced catalysts. Thus, this work provides a transformative foundation for developing more efficient and selective electrocatalysts, ultimately enabling enhanced control over catalytic outcomes.