Homogeneously Mixed Cu–Co Bimetallic Catalyst Derived from Hydroxy Double Salt for Industrial-Level High-Rate Nitrate-to-Ammonia Electrosynthesis

Electrocatalytic nitrate reduction reaction (NO₃RR) presents an innovative approach for sustainable NH₃ production. However, selective NH₃ production is hindered by the multiple intermediates involved in the NO₃RR process and the competitive hydrogen evolution reaction. Hence, the development of highly efficient NO₃RR catalysts is paramount. Herein, we report highly efficient bimetallic catalysts derived from hydroxy double salt (HDS). Under NO₃RR conditions, Cu₁Co₁-HDS undergoes in situ reconstruction, forming nanocomposites of homogeneously distributed metallic Cu⁰ and Co(OH)₂. Reconstruction-induced Cu⁰ rapidly converts NO₃^- to NO₂^-, which is further hydrogenated to NH₃ by Co(OH)₂. Homogeneously mixed Cu and Co species maximize this synergistic effect, achieving outstanding NO₃RR performance including the highest NH₃ yield rate (4.625 mmol h^-1 cm^-2) reported for powder-type NO₃RR catalysts. Integration of Cu₁Co₁-HDS with a commercial Si solar cell attained 4.53% solar-to-ammonia efficiency from industrial wastewater-level concentrations of NO₃^- (2000 ppm), demonstrating practical application potential for solar-driven NH₃ production. This study provides a strategy for enhancing the NH₃ yield rate by optimizing the compositions and distributions of Cu and Co.