Unveiling Ionized Interfacial Water‐Induced Localized H* Enrichment for Electrocatalytic Nitrate Reduction

Abstract Electrocatalytic nitrate reduction reaction (NO 3 RR) is a process that requires the participation of eight electrons and nine protons. The regulation of active hydrogen (H*) supply and a deep understanding of related processes are necessary for improving the ammonia yield rate and Faradaic efficiency (FE). Herein, we synthesized a series of atomically precise copper‐halide clusters Cu 2 X 2 (BINAP) 2 (X=Cl, Br, I), among which the Cu 2 Cl 2 (BINAP) 2 cluster shows the optimal ammonia FE of 94.0 % and an ammonia yield rate of 373 μmol h −1 cm −2 . In situ experiments and theoretical calculations reveal that halogen atoms, especially Cl in Cu 2 Cl 2 (BIANP) 2 , can significantly affect the distance of alkali metal‐ionized water on the catalyst surface, which can promote the water dissociation to enhance the localized H* enrichment for the continues hydrogenation of nitrate to ammonia. This work explains the role of H* in the hydrogenation process of NO 3 RR and the importance of localized H* enrichment strategy for improving the FEs.