Unlocking the potential: key roles of interfacial water in electrocatalysis

Interfacial water, serving as a subtle yet powerful performance modulator, plays a pivotal role in various electrochemical technologies due to its unique configurations and dynamic properties. Especially in the past decade, advances in electrocatalyst research, experimental characterization and theoretical modeling have significantly deepened the understanding of interfacial water's role in electrocatalytic systems. These as-obtained insights not only elucidate the dynamic behavior and structural properties of interfacial water but also highlight its importance in optimizing reaction pathways and improving electrocatalytic performance. Therefore, the understanding and regulation of interfacial water is an important topic in electrocatalytic research, and motivated us to compile this review. This review starts with a thorough analysis of interfacial water's properties and behaviors relevant to the electrocatalysis including structural types, water networks, rigidity and molecular orientation. Then, the specific roles of interfacial water in electrocatalysis are subsequently analyzed and classified as a co-catalyst, a masking agent, a regulator of reaction intermediates, and an inducer of catalyst reconfiguration. Next, some advanced experimental characterization and computational methods are presented to collectively probe the interfacial water, which is critical to capture accurate structural information. Furthermore, we present a comprehensive overview of key strategies for modulating the properties and behaviors of interfacial water to enhance the electrocatalytic performance of representative reactions at the electrolyte and catalyst levels, with emphasis on the specific mechanisms behind these modulation approaches. Finally, we discuss current challenges and future opportunities in this field, aiming to inspire the design of more advanced electrocatalytic systems.