Single Ag Atoms Induce Ag-N/O Bonds on WO₃ for Ultrastable Acid Ammonia Synthesis

Ammonia from nitrate-containing wastewater demands the catalysts with high activity, stability, and selectivity toward acidic electrochemical nitrate reduction owing to the corrosion effect of the catalyst and the competitive hydrogen evolution reaction (HER). Herein, we synthesized single Ag atoms induced Ag-N/O bonds on one-dimensional WO₃ nanowires for highly efficient and stable electrochemical nitrate reduction to ammonia under acidic conditions. The resultant catalyst achieved a Faradaic efficiency (FE) of ammonia exceeding ∼90% over a potential range of -0.6 to -0.2 V_RHE with a maximum FE approaching 100% at -0.4 V_RHE and a maximum NH₃ yield at -0.55 V_RHE. Importantly, the catalyst maintained a current density at 480 mA cm^-2 over 1100 h with a stable FE of ∼94%. By integrating the catalyst into a membrane electrode assembly (MEA), we succeeded in obtaining an NH₃ production rate of 12.75 mmol h^-1 at -4 V and maintained the stability for over 30 h with FE > 90%. Experimental and theoretical analysis have demonstrated that the formation of Ag-N/O bonds enhanced nitrate adsorption and lowered the energy barrier for the rate-determining step of *NO→*NHO, thereby considerably improving the efficiency of ammonia synthesis and inhibiting HER at amperometric current densities. This work provides insights into acidic nitrate reduction for ammonia electrosynthesis, which develops corrosion-resistant electrocatalysts for energy conversion.