Increasing electrocatalytic nitrate reduction activity by controlling adsorption through PtRu alloying

Nitrate produced from industrial and agricultural processes has imbalanced the global nitrogen cycle. Electrocatalytic reduction is a sustainable route to remediate nitrate while generating products such as ammonia or N2. Here we report the surface-area normalized activity of platinum-ruthenium (PtxRuy/C) catalysts of different compositions (x = 48–100%) for electrocatalytic nitrate reduction, chosen based on screening using a computational activity volcano plot. The PtxRuy/C alloys are more active than Pt/C, with Pt78Ru22/C six times more active than Pt/C at 0.1 V vs. RHE, and ammonia faradaic efficiencies of 93–98%. Density functional theory calculations predict maximum activity at 25 at% Ru, consistent with experiments. This maximum is due to a transition from nitrate dissociation as the rate determining step to a new rate-determining step at higher Ru content. This study demonstrates how electrocatalyst performance is tunable by changing the adsorption strength of reacting species through alloying.