Cathodic Interfacial Oxidation‐Induced Rapid Synthesis of Nickel Phosphate Electrocatalyst from Wastewater for Acidic Nitrate‐to‐Ammonia Conversion

Abstract The electrochemical nitrate reduction reaction (NO 3 − RR) presents a promising strategy for simultaneous wastewater remediation and ammonia synthesis. However, the fabrication of efficient, stable, and economically viable electrocatalysts remains a significant challenge. Addressing this, we report the rapid (14 min) electrodeposition of an amorphous nickel phosphate catalyst directly onto a metallic foam cathode, utilizing nickel plating wastewater as a precursor under high‐current conditions. This catalyst exhibits exceptional performance in acidic media, achieving a Faradaic efficiency of 96.6% for ammonia at −0.5 V (versus RHE) in 10 mM NO 3 − solution, alongside remarkable electrochemical stability exceeding 20 h. We attribute the catalyst formation to the oxidation of hypophosphite at the cathode interface during high current polarization and its subsequent co‐deposition with Ni 2+ ions. When applied to actual nickel plating wastewater at 200 mA cm −2 , the system demonstrated relatively stable operation for 30 h and successfully recovered ammonium sulfate. Combined experimental and theoretical analyses reveal the origin of the superior NO 3 − RR activity. This work provides an innovative waste‐derived strategy for the rapid synthesis of high‐performance catalysts and advances the sustainable recovery of nitrogen, phosphorus, and nickel from industrial waste streams.