Promoting effects of potassium on ammonia production from electrochemical nitrate reduction over nano-crystal nickel

Potassium ions (K + ) in electrolyte can stimulate the electrochemical nitrate reduction to ammonia (NRA) while the mechanism behind this improvement is still underexamined. Here, the effects of K + on regulating the NRA over a nano-crystal nickel catalyst are thoroughly investigated. The catalyst exhibits excellent NRA performance with an NH 3 yield rate of 167.98 ± 1.41 μmol h −1 cm −2 , selectivity of 95.56%, and faradaic efficiency of 89.23%. The NH 3 yield rate can further increase to 214.10 ± 4.22 μmol h −1 cm −2 with 50% K + . In situ Raman and density functional theory (DFT) revealed that K + facilitates NO 3 − adsorption but hinders sulfate (SO 4 2− ) adsorption on the catalyst. In addition, the efficiency of active hydrogen (*H) generation is elevated, which facilitates the NRA pathway with *NH as the intermediate over the catalyst. The present result is beneficial for gaining a mechanistic understanding of the promoting effects of ions on NRA and developing electrolyte engineering to improve the performance of NH 3 production. K + in the electrolyte promoted the adsorption of NO 3 − on the nano-crystal nickel catalyst surface and the generation of *H. Consequently, the sluggish NO 3 − reduction was ameliorated, and elevated performance of NRA was obtained.