Selective NOx– Electroreduction to Ammonia on Isolated Ru Sites

Nitrate and nitrite (NO x – ) are widespread contaminants in industrial wastewater and groundwater. Sustainable ammonia (NH 3 ) production via NO x – 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 3 generation relies on the robust catalyst. A specific consideration in designing selective NO x – -to-NH 3 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 x – into NH 3, with maximal Faradaic efficiencies of 97.8% (NO 2 – reduction) and 72.8% (NO 3 – 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 x – -to-NH 3 conversion on single-atom Ru sites.