Coupling of Nitrate Electroreduction to Ammonia with Sulfide Electrooxidation to Sulfur for High‐Efficiency Wastewater Treatment and Resource Recovery

Electrochemical nitrate reduction to ammonia (NO₃RR) offers a sustainable alternative to conventional ammonia synthesis. However, its practical efficiency is hindered by the high energy consumption associated with the sluggish anodic oxygen evolution reaction (OER). Replacing OER with favorable sulfide oxidation reaction (SOR) significantly lowers cell voltage while converting nitrate and sulfide pollutants into valuable ammonia and sulfur. In this study, amorphous NiP_x and CoS_x catalysts are electrodeposited on nickel foam (NF) as high-performance cathode and anode, respectively. The NiP_x/NF cathode achieves an impressive NH₃ yield rate of 0.332 mmol h^-1 cm^-2 with 95.4% Faradaic efficiency (FE) at -0.2 V versus RHE, while the CoS_x/NF anode demonstrates a low SOR overpotential of 0.376 V versus RHE at 100 mA cm^-2. The coupled NO₃RR || SOR system demonstrates a 1.538 V reduction in cell voltage at 10 mA cm^-2 compared to a conventional NO₃RR || OER system, resulting in a 73% reduction in energy consumption for ammonia production. This work not only provides guidance for rationally designing high-performance NO₃RR and SOR electrocatalysts, but also paves an efficient route for simultaneous nitrate/sulfide wastewater treatment and resource recovery, demonstrating great application potential.