Engineering Interfacial Water for Advanced Electrocatalytic CO2 Reduction: From Molecular Understanding to Materials Design.

Electrocatalytic CO2 reduction (CO2RR) offers a direct pathway for converting CO2 gas into fuels and value-added chemicals. However, achieving CO2RR with high activity and stability remains a significant challenge. While previous research has predominantly focused on catalyst design, the role of interfacial water has often been overlooked. Interfacial water can act as the primary proton donor, directly influencing the competition between CO2RR and the hydrogen evolution reaction. Moreover, the dynamic hydrogen-bond network of interfacial water can significantly alter the water dissociation barrier, thereby enhancing selectivity toward CO2RR products. This review systematically summarizes the fundamental properties of interfacial water in CO2RR, classifies the strategies for modulating interfacial water, and discusses the applicability of these strategies and their impact on CO2RR performance. Particular emphasis is placed on the effect of interfacial water structural evolution on the CO2RR mechanism, as well as the corresponding characterization techniques. This review provides a structured framework for the study of interfacial water in CO2RR and offers guidance for the rational design of high-efficiency catalysts.