Construction of a Synergistic Ag/Co(OH) ₂ Composite for Efficient Nitrate Electroreduction to Ammonia

Developing efficient electrocatalysts for the nitrate reduction reaction (NO 3 RR) to produce ammonia is of great significance. In this work, a Ag nanoparticle-modified Co(OH) 2 catalyst was prepared by electrodeposition and liquid-phase deposition. The Ag/Co(OH) 2 composite exhibits significantly enhanced NO 3 RR performance in comparison with Co(OH) 2, achieving a high NH 3 FE and a yield rate of 95.6% and 97.1 μmol h –1 cm –2 at −0.6 V in a neutral medium. Comprehensive characterizations confirm the strong interfacial coupling between Ag and Co(OH) 2, while electrochemical studies reveal synergistic effects that simultaneously enhance nitrate adsorption and moderate hydrogen adsorption. Such a probable NO 3 RR tandem mechanism is proposed in which Ag dominates the initial 2e – pathway (*NO 3 →*NO 2 ) and Co(OH) 2 was prior in the subsequent *NO hydrogenation into *NH 3 . This work provides both a novel catalyst and fundamental insights into the composite material design for electrochemical NO 3 RR.