pH-Universal Electrocatalytic Nitrate-to-Ammonia Reduction on Ruthenium-Decorated Copper Foam

Abstract Electrocatalytic reduction reaction of nitrate to ammonia (NO3RR) has emerged as a promising strategy that couples nitrate pollutant remediation with sustainable NH3 production. Practical nitrate-containing industrial wastewater usually presents a wide pH distribution range, which puts forward an urgent requirement for pH-adaptive NO₃RR catalysts with high ammonia selectivity. Conventional NO3RR catalysts fail to deliver high NH3 Faradaic efficiency under extreme acidic or alkaline conditions, mainly due to uncontrollable competitive adsorption of hydrogen intermediates on active sites. Herein, we report a ruthenium-decorated copper foam catalyst (RuCuF@PUS) fabricated via a facile two-step electrodeposition method, which achieves exceptional NO3RR performance across a wide pH window of 1-12. The interconnected porous framework enables efficient mass transfer, while the precisely designed dual active sites endow Cu with strong nitrate adsorption and activation capability, and Ru with accelerated sequential hydrogenation kinetics. In acidic condition, the catalyst achieves a remarkable ammonia yield rate of 457.56 µmol/h·cm2 at −0.4 V vs. RHE, with a peak Faradaic efficiency of 90.96%. Furthermore, a proof-of-concept alkaline-acidic hybrid Zn–NO3 battery assembled with the RuCuF@PUS cathode and real nitrate-containing wastewater as electrolyte achieves an open-circuit voltage of 1.29 V and a peak power density of 25.93 mW/cm2.