Refining the active phases of silver/nickle-based catalysts achieves a highly-selective reduction of nitrate to ammonium at low overpotential

Abstract

The electrocatalytic conversion of NO3‾ to NH3 (NO3RR) with elevated activity and exceptional selectivity at low potential remains a formidable challenge. Herein, the A-Ag@Ni/Ni(OH)2 NWs with atomic-level Ag/Ni interfaces were synthesized via electrochemical activation of Ag@Ni/Ni(OH)2 NWs at −1.05 V vs. RHE for 1 hour, and subsequently employed for electrocatalytic NO3RR. Specially, Ag sites could afford active centers for the adsorption of NO3‾ and convert it to NO2‾. Furthermore, Ni/Ni(OH)2 sites as vibrant centers for electrocatalytic H2O splitting, generating atomic H on the catalyst surface (Hads), thereby facilitating the rapid conversion of NO2‾ to NH3 via the Hads-mediated pathway. DFT calculations further substantiate that the Hads-mediated pathway is thermodynamically more favorable than the electron reduction pathway, the former of which facilitates the generation of NH3 and is an energy-efficient process, thus, the A-Ag@Ni/Ni(OH)2 NWs show outstanding electrocatalytic activity and selectivity for NO3‾-to-NH3 transformation at low potential.