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

Electrocatalytic nitrate reduction reaction (NORR) 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 CuX(BINAP) (X=Cl, Br, I), among which the CuCl(BINAP) cluster shows the optimal ammonia FE of 94.0 % and an ammonia yield rate of 373 μmol h cm. In situ experiments and theoretical calculations reveal that halogen atoms, especially Cl in CuCl(BIANP), 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 NORR and the importance of localized H* enrichment strategy for improving the FEs.