Tandem Electrocatalytic Reduction of Nitrite to Ammonia on Rhodium–Copper Single Atom Alloys

Abstract

Electrocatalytic reduction of NO2− to NH3 (NO2RR) presents a fascinating approach for simultaneously migrating NO2− pollutants and producing valuable NH3. In this study, single-atom Rh-alloyed copper (CuRh1) is explored as a highly active and selective catalyst toward the NO2RR. Combined theoretical calculations and in situ FTIR/EPR spectroscopic experiments uncover the synergistic effect of Rh1 and Cu to promote the NO2RR energetics of CuRh1 through a tandem catalysis pathway, in which Rh1 activates the preliminary adsorption and hydrogenation of NO2− (NO2− → *NO2 → *NOOH → *NO), while the generated *NO on Rh1 is then transferred on Cu substrate which promotes the rate-determining step of *NO → *NHO toward the NH3 synthesis. As a result, CuRh1 equipped in a flow cell presents an unprecedented NH3 yield rate of 2191.6 µmol h−1 cm−2 and NH3-Faradaic efficiency of 98.9% at a high current density of 322.5 mA cm−2, as well as long-term stability for 100 h electrolysis.