Stabilizing Cu ^δ+ Species via Ni,Co Comodification for Promoted Electrocatalytic Nitrate Reduction

Electrochemical nitrate reduction reaction (NO 3 RR) for ammonia (NH 3 ) production is considered as a sustainable alternative to the Haber–Bosch process due to its renewable nature and environmental friendliness. Nevertheless, the sluggish reaction kinetics of the NO 3 RR severely limits the NH 3 yield and Faradaic efficiency, hindering its practical applications. Copper (Cu) catalysts, although widely employed, suffer from *NO 2 accumulation and an insufficient active hydrogen (*H) supply, resulting in unsatisfactory NO 3 RR performance. Herein, to refine the catalytic properties of Cu-based catalysts, a robust Ni,Co-codoped CuO x (Ni,Co-CuO x ) nanorod catalyst is designed, which would be in situ reconstructed into stable Ni,Co–Cu/CuO x hybrids during NO 3 RR. Experimental and theoretical results reveal that Ni,Co codoping effect synergistically stabilizes Cu δ+ species through Ni/Co–O–Cu bonds and maintains the Cu/CuO x structure, which acts as the main active center for NO 3 RR. Meanwhile, Ni,Co codopants accelerate *H desorption, as well as suppress hydrogen evolution side reaction, leading to a favorable balance between *H supply and intermediate adsorption. Combining the above advantages, the Ni,Co-CuO x catalyst delivers an ultrahigh NH 3 yield rate of 130.64 mg h –1 cm –2 with a Faradaic efficiency of 98.53% under ampere current densities. This work innovatively proposes a strategy for immobilizing Cu δ+ species and offers new insights into stable catalyst design for NO 3 RR. The Ni,Co-CuO x electrocatalyst converts waste nitrate to ammonia with superior performance, offering a low-carbon, sustainable alternative to the Haber–Bosch process.