Modulating dynamic atomic hydrogen generation and utilization for selective electrocatalytic ammonia recovery from low-concentration nitrate-containing wastewater

Herein, a copper-doped nickel phosphide (Cu x Ni 2-x P) electrode with a tailored metal d-band center was designed to boost ammonia (NH 3 ) selectivity during electrocatalytic nitrate (NO 3 − ) reduction (NO 3 RR) by modulating atomic hydrogen (H*) behavior. The Cu doping accelerated both the Volmer step of water splitting to form H* and the H* -mediated hydrogenation steps for NH 3 production, addressing the mismatch between H* supply and utilization. Consequently, the Cu x Ni 2-x P electrode achieved 100 % NO 3 − conversion efficiency and 99.2 % NH 3 selectivity at a low NO 3 − concentration of 50 mg L −1 , outperforming Ni 2 P and Cu counterparts. The crucial role of H* in the performance enhancement was elucidated via in-situ characterizations and density functional theory (DFT) calculations . Furthermore, an integrated device combining NO 3 RR, organic pollutant degradation and NH 3 recovery was constructed, demonstrating its scalability for practical wastewater treatment. This study paves the way for collaboratively addressing environmental and energy challenges through improving NH 3 recovery from nitrate-laden wastewater. • Cu doping modulates the d-band center of the electrode. • Achieving dynamic equilibrium between H* supply and in situ consumption. • Cu x Ni 2-x P electrode exhibits excellent performance at a low NO 3 − concentration. • An integrated device combining NO 3 RR, pollutant degradation and NH 3 recovery.