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

Abstract Electrocatalytic reduction of NO 2 − to NH 3 (NO 2 RR) presents a fascinating approach for simultaneously migrating NO 2 − pollutants and producing valuable NH 3 . In this study, single‐atom Rh‐alloyed copper (CuRh 1 ) is explored as a highly active and selective catalyst toward the NO 2 RR. Combined theoretical calculations and in situ FTIR/EPR spectroscopic experiments uncover the synergistic effect of Rh 1 and Cu to promote the NO 2 RR energetics of CuRh 1 through a tandem catalysis pathway, in which Rh 1 activates the preliminary adsorption and hydrogenation of NO 2 − (NO 2 − → *NO 2 → *NOOH → *NO), while the generated *NO on Rh 1 is then transferred on Cu substrate which promotes the rate‐determining step of *NO → *NHO toward the NH 3 synthesis. As a result, CuRh 1 equipped in a flow cell presents an unprecedented NH 3 yield rate of 2191.6 µmol h −1 cm −2 and NH 3 ‐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.