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

Abstract

Developing efficient electrocatalysts for the nitrate reduction reaction (NO3RR) 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 NO3RR performance in comparison with Co(OH)2, achieving a high NH3 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 NO3RR tandem mechanism is proposed in which Ag dominates the initial 2e- pathway (*NO3→*NO2) and Co(OH)2 was prior in the subsequent *NO hydrogenation into *NH3. This work provides both a novel catalyst and fundamental insights into the composite material design for electrochemical NO3RR.