Interfacial Water Networks Regulate Solid-Liquid Contact Electrification.

Elucidating the mechanisms of solid-liquid contact electrification (CE) is pivotal for advancing technologies such as water-based energy harvesting, digital microfluidics, self-powered sensing systems, and chemical synthesis. Despite extensive progress, current research has primarily focused on identifying charge carriers, while the regulatory role of interfacial water remains poorly understood. Here, we demonstrate that interfacial water serves as an active regulator of solid-liquid CE through its structure and interactions with solid surfaces. By systematically tuning interfacial water environments, we reveal that water-water interactions within the hydrogen-bond (H-bond) network and water-solid interactions at the interface cooperatively regulate CE efficiency. In situ interfacial characterization and theoretical calculations show that modifying interfacial water structures alters molecular configurations and strengthens water-solid coupling, thereby facilitating interfacial charge transfer. Furthermore, we develop a mid-infrared (MIR)-driven vibrational excitation strategy for regulating interfacial water structures, leading to enhanced CE performance and improved hydrogen peroxide production in a contact-electro-catalysis system. This work establishes the interfacial water structure as an important factor governing solid-liquid CE and provides a novel strategy for controlling water-mediated interfacial charge transfer.