Controlled Defective Engineering on CuIr Catalyst Promotes Nitrate Selective Reduction to Ammonia

Electrochemical nitrate reduction reaction (NO₃^-RR) is a promising low-carbon and environmentally friendly approach for the production of ammonia (NH₃). Herein, we develop a high-temperature quenched copper (Cu) catalyst with the aim of inducing nonequilibrium phase transformation, revealing the multiple defects (distortion, dislocations, vacancies, etc.) presented in Cu, which lead to low overpotential for NO₃^-RR and high efficiency for NH₃ production. Further loading a low content of iridium (Ir) species on the Cu surface improves the reactivity and ammonia selectivity. The resultant CuIr electrode exhibits a Faradaic efficiency of 93% and a record yield of 6.01 mmol h^-1 cm^-2 at -0.22 V_RHE exceeding those of state-of-the-art NO₃^-RR catalysts. Detailed investigations have demonstrated that the synergistic effect between multiple defects and Ir decoration effectively regulate the d-band center of copper, change the adsorption state of the catalyst surface, and promote the adsorption and reduction of intermediates and reactants. The strong H* adsorption ability of the Ir element provides more active hydrogen for the generation of ammonia, promoting the reduction of nitrate to NH₃.