Theoretical Screening of Transition Metal-N₄-Doped Graphene for Electroreduction of Nitrate

Electrochemical nitrate reduction reaction (NO₃RR) is an advantageous conversion technology for nitrate removal and ammonia synthesis. Single-atom catalysts, owing to their utmost metal atom utilization efficiency, are promising electrocatalysts for NO₃RR but are rarely investigated in systematic ways. In this study, a theoretical screening is performed on transition metal-N₄-doped graphene (TM-N₄/C) as active and selective electrocatalysts for NO₃RR, where detailed reaction mechanisms and activity origins are explored. Volcano plots of activity trends show that Cu- and Pt-N₄/C are highly active for NO₃RR following the NH₃and N₂formation pathways, respectively, whose activities can be attributed to the optimal NO and N adsorptions. In addition, a contour plot of selectivity trend shows that Re- and Pt-N₄/C are highly selective toward NH₃and N₂formations, respectively. This work provides theoretical insights into the rational design of TM-N₄/C catalysts for NO₃RR and opportunities for efficient nitrate removal and ammonia synthesis strategies.