Copper–Cobalt Atomically Dispersed Catalysts for Selective Ammonia Electrosynthesis from Dilute Nitrate in Low-Concentration Electrolyte

Abstract

Developing effective electrocatalysts that can convert low-concentration nitrate (NO3–) into ammonia (NH3) in dilute electrolytes remains a major challenge. In this work, high-performance atomically dispersed CuCo catalysts (CuCo-ADCs) were prepared using a hydrothermal route. When tested in electrolyte containing 50 ppm NO3–-N and 5 mM K2SO4 (supporting electrolyte), the catalyst delivered a high NH3 Faradaic efficiency (FE) of 92.15%, ammonia selectivity of 96.33%, and NH3 production rate of 281.28 μg h–1 cm–2 at –0.6 V vs reversible hydrogen electrode (RHE). Electrochemical measurements indicated reduced solution diffusion resistance for this catalyst. After 10 h of continuous operation, more than 85% of the initial catalytic activity could be retained. Mechanistic characterizations suggested that the atomic-level dispersion accelerated reaction kinetics and suppressed the competing hydrogen evolution reaction. Such improvement originated from the optimized *NO3 adsorption and decreased N═O bond dissociation energy through bimetallic synergy. Within this catalytic system, Cu drove the nitrate reduction reaction, Co was responsible for key bond cleavage, and Ni promoted hydrogenation steps as well as product desorption. This study offers alternative design ideas for atomically dispersed catalysts intended for resource recovery from low-concentration nitrate-rich wastewater. The present catalytic system may be applied for simultaneous nitrogen removal and ammonia generation in practical wastewater treatment.