In situ insights into boosting active hydrogen on reconstructed multiphase Heterointerfaces for efficient...

Copper-based catalysts have emerged as promising candidates for the electrochemical nitrate reduction reaction (NO₃RR) to produce ammonia (NH₃). Achieving selective NH₃ synthesis with high Faradaic efficiency and productivity remains a significant challenge. Herein, we investigate the manipulation of dynamic Cu⁰/Cu⁺/Cu²⁺ multiphase heterointerfaces using an electrochemical reconstruction strategy on a carbon-coated CuO/Cu₂O@C catalyst during NO₃RR. An intriguing catalytic relationship is revealed by electrochemical analysis that the formation of the dynamic Cu⁰/Cu⁺/Cu²⁺ interface as superior active sites enhances the selective conversion of NO₃^- to NH₃. The maximum NH₃ Faradaic efficiency (95.5%) and productivity (13.5 mg·h^-1·mg_cat^-1) are achieved on multiphase heterointerfaces under pH-neutral conditions. As revealed by in situ structural analysis and density functional theory (DFT) calculations, multiphase heterointerfaces facilitate water activation, boost hydrogen supply, and lower the energy barrier for the rate-determining step of *NO-to-*N, thereby promoting the selectivity and Faradaic efficiency of NH₃. This discovery paves the way for novel design of Copper-based catalysts, featuring improved activity and selectivity to promote NO₃RR.