Selective NO Electroreduction to Ammonia on Isolated Ru Sites.

Nitrate and nitrite (NO) are widespread contaminants in industrial wastewater and groundwater. Sustainable ammonia (NH) production via NO electroreduction provides a prospective alternative to the energy-intensive industrialized Haber-Bosch process. However, selectively regulating the reaction pathway, which involves complicated electron/proton transfer, toward NH generation relies on the robust catalyst. A specific consideration in designing selective NO-to-NH catalysts should meet the criteria to suppress competing hydrogen evolution and avoid the presence of neighboring active sites that are in favor of adverse N-N coupling. Nevertheless, efforts in this regard are still inadequate. Herein, we demonstrate that isolated ruthenium sites can selectively reduce NO into NH, with maximal Faradaic efficiencies of 97.8% (NO reduction) and 72.8% (NO reduction) at -0.6 and -0.4 V, respectively. Density functional theory calculations simulated the reaction mechanisms and identified the *NO → *NOH as the potential rate-limiting step for NO-to-NH conversion on single-atom Ru sites.