Electrochemical Nitric Oxide Reduction on Metal Surfaces

Electrocatalytic denitrifification is a promising technology for removing NOx species (NO3⁻, NO2⁻ and NO). For NO_x electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NO_xRR. At low potential we classify metals by the binding of ∗NO versus ∗H. Analogous to classifying CO2 reduction by ∗CO vs ∗H, Cu is able to bind ∗NO while not binding ∗H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity-volcano. For metals that does not bind NO the reaction stops at NO, similar to CO₂-to-CO. At potential above 0.3 V vs RHE, we speculate a low barrier for N coupling with NO causing N₂O formation. The work provide a clear strategy for selectivity and aims to inspire future research on NO_xRR.