• • Co0.5Cu1.5(OH)PO4 achieves 99.0% Faradaic efficiency for NH3 at 200 mA cm−2 in 1 M NO3−, with a production rate of 9.18 mg h−1 cm−2, outperforming other Co/Cu ratios and sustaining >200 h continuous operation, indicating industrial viability for high-strength nitrate wastewater treatment.
• • The energy barrier difference between NO3RR and H* generation on Co0.5Cu1.5(OH)PO4 is 0.18 eV, versus 0.38 eV on Cu2(OH)PO4, demonstrating a 53% reduction in HER competition, which is critical for achieving high selectivity at industrially relevant current densities.
• • DFT calculations reveal that Co sites dissociate water to supply H*, while Cu sites drive deoxygenation and hydrogenation of intermediates (*NO2, *NO), lowering the rate-determining step energy barrier; this tandem mechanism enables efficient nitrate-to-ammonia conversion at high concentrations.
• • The volcano-shaped activity dependence on Co/Cu ratio underscores the necessity of balancing H* generation and consumption; optimal performance at Co0.5Cu1.5(OH)PO4 highlights the importance of precise atomic-ratio control for circumventing scaling relations in electrocatalysis.