Steam-Reformed Dispersive Sites with Cu⁰-Cu⁺ Interface for Electroreduction of Nitrate to Ammonia

Electrocatalysis represents an attractive approach for nitrate recovery from wastewaters through catalytic nitrate reduction (NO₃RR) to produce value-added ammonia. Although metallic copper catalysts are increasingly utilized, their nanoparticles tend to agglomerate in reactive atmospheres, degrading the catalytic performance. This study proposed a methanol steam reforming strategy to tailor metallic copper catalysts, generating dispersed sites with a unique Cu⁰-Cu⁺ interface. During the 120 h reformation process, the mean size of Cu particles decreases from 80.03 to 22.13 nm. The reformed catalyst achieves a Faraday efficiency of 87% and a NH₃ production rate of 10.39 mg h^-1 mg_cat^-1 at -0.4 V, along with remarkable long-term durability. The redispersion of coupling Cu sites enhances the adsorption and hydrogenation of key intermediates (*NO₂) in NO₃RR, facilitating efficient NH₃ production. Furthermore, the Zn-NO₃^- battery with a re-Cu/C-120 cathode delivers an open-circuit voltage of 1.27 V and a power density of 8.46 mW cm^-2. These results present an effective strategy for constructing dispersed active sites on metallic nanoparticles for advanced electrocatalysis.