Ultralow overpotential 465 mV: Ni and Fe synergistically promote the conversion of nitrate to ammonia

Abstract

Abstract The electrochemical nitrate reduction reaction (NO3RR) can effectively remove the nitrate from effluent and convert it to usable ammonium. However, the high reaction overpotential and the unclear mechanism hinder the development of NO3RR. In this study, a NiFe nanosheet electrocatalyst is developed and employed as a platform to elucidate the NO3RR reaction mechanism. The as-prepared NiFe electrocatalyst exhibits an ultralow overpotential of 465 mV, and reaches the yield of ammonia 1329.7 µmol cm− 2 h− 1, the Faraday efficiency 96.9% at -0.2 V vs. RHE. In-situ X-ray absorption spectroscopy (XAS) and Raman spectrum reveal that Ni is the nitrate adsorption site, where the two-proton transfer step (*NO3-→*NO2-) takes place. Meanwhile, the Fe is the water absorption and dissociation site, which can provide more proton to Ni, promoting the further transformation of *NO2- to NH3.