In situ insights into boosting active hydrogen on reconstructed multiphase Heterointerfaces for efficient nitrate-to-Ammonia conversion

Copper-based catalysts have emerged as promising candidates for the electrochemical nitrate reduction reaction (NO 3 RR) to produce ammonia (NH 3 ). Achieving selective NH 3 synthesis with high Faradaic efficiency and productivity remains a significant challenge. Herein, we investigate the manipulation of dynamic Cu 0 /Cu + /Cu 2+ multiphase heterointerfaces using an electrochemical reconstruction strategy on a carbon-coated CuO/Cu 2 O@C catalyst during NO 3 RR. An intriguing catalytic relationship is revealed by electrochemical analysis that the formation of the dynamic Cu 0 /Cu + /Cu 2+ interface as superior active sites enhances the selective conversion of NO 3 − to NH 3 . The maximum NH 3 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 NH 3 . This discovery paves the way for novel design of Copper-based catalysts, featuring improved activity and selectivity to promote NO 3 RR.