Synergistic Cu–Co Bimetallic Catalysis on Hierarchical Carbon for Electrocatalytic Nitrate Reduction to Ammonia with In Situ Recovery

RR) to ammonia offers a promising route for sustainable nitrogen valorization. However, its translation into practice is held back by insufficient selectivity and high energy and capital costs linked to downstream ammonia separation. This study addresses these limitations through the codesign of catalyst and reactor. The integrated device comprises CuCo oxides precisely loaded onto a hierarchically porous oxidized activated carbon (OAC), with a custom-built flow-electrode reactor optimized for efficient in situ ammonia recovery. The developed CuCo@OAC catalyst demonstrates exceptional performance in a neutral aqueous electrolyte, achieving ∼100% ammonia selectivity, a high Faradaic efficiency of 98.1%, and a 97.2% nitrate conversion rate. Crucially, the integrated approach delivers a remarkable 95.7% overall ammonia recovery rate, demonstrating effective translation from material properties to system-level performance. Mechanistic investigations reveal that the superior activity stems from a synergistic interaction between the Cu and Co active sites; Cu predominantly facilitates nitrate adsorption and activation, while Co actively promotes water dissociation to generate reactive hydrogen species, all effectively channeled by the hierarchical porous architecture. This research not only introduces a highly efficient and selective catalyst-reactor system for nitrate valorization but also establishes a validated framework for catalyst-reactor codesign, offering a significant step toward practical and scalable environmental electrochemical technologies for water treatment and resource recovery.