Cooperating oxidative half-reaction deactivate electrocatalyst for nitrate reduction in real wastewater

Abstract

Electrocatalytic nitrate reduction to ammonia (eNO₃RA) paves a promising way toward nitrate mitigation and ammonia recovery from real wastewater. While the complex constituents in real wastewater raise concerns about the stability of catalysts. Here, the comprehensive investigation of the stability of easy-to-prepare Cu_xO nanowires for eNO₃RA is performed in real wastewater. Irreversible catalyst deactivation is observed in short-term operation for eNO₃RA and ammonia selectivity decreases from 82.02 to 28.37 % due to the ineffective hydrogenation of intermediates. Conversely, the performance decrease for long-term eNO₃RA in confined electrolytes can be recovered with oven drying of the catalyst. The irreversible deactivation of the catalyst proceeds with the aggregation of nanowires as the oxidation of Cu⁺ to Cu²⁺. Chloride ion is recognized as the main contributor due to the cooperating oxidative half-reaction at the anode. These findings emphasize the need for careful consideration of the catalysts’ stability in the design of electrochemical systems for eNO₃RA.