Theoretical insight into electrochemical nitrate reduction on transition metal iron doped graphdiyne

Production of ammonia (NH₃) by electrocatalytic reduction of nitrate (NO₃RR) not only eliminates harmful pollution, but also provides a way to reduce the energy consumption associated with predominated Haber-Bosch process. However, realization of this process still faces many challenges because of the complexity of the reaction mechanism. Here we investigated the catalytic activity and selectivity of a series of graphdiyne supported single atom catalysts (SACs), namely TM/GDY, for the reduction of N$O_3^{-}$ to NH₃ by first-principles calculations. Among the 10 SACs studied, Fe/GDY was found to have good catalytic performance, consistent with the fact that the Fe-doped GDY molecular layer was located near the top of the volcano plot, with a reaction limit potential of −0.44 V and showed excellent selectivity in inhibiting the competitive hydrogen evolution reaction (HER). The formation of the by-products NO₂, NO, N₂O and N₂ on Fe/GDY requires a considerable energy barrier, which ensures high selectivity. Furthermore, detailed electronic property analyses indicate that the GDY can work as an electron repository to effectively balance the charge transfers during the reaction process. This study not only offers an eligible NO₃RR electrocatalyst but also provides an atomic understanding of the mechanisms of the NO₃RR process behind.