Breaking scaling relations and boosting ammonia synthesis in nitrogen reduction with V-containing heteronuclear double metal atoms

The electrochemical nitrogen reduction reaction (NRR), powered by renewable electricity, offers a promising pathway for sustainable ammonia production. The multi-step nature of this reaction introduces inherent challenges due to the well-known scaling relations between the adsorption energies of various intermediates, which limit overall efficiency. By using density functional theory calculations, in this study we evaluated the NRR activity of dual-metal atoms, specifically vanadium (V) paired with 3d transition metals, anchored on graphdiyne (V-TM@GDY, where TM = Sc similar to Cu). We first found that the adsorption energies of various NRR intermediates did not follow the scaling relationships any more as expected. We further identified an optimized volcano-shaped correlation between electron transfer to the adsorbed N2 molecule and the limiting potential for ammonia synthesis (UL(NH3)) across all heteronuclear V-TM@GDY dual-atom catalysts (DACs). Intriguingly, through an "acceptance-donation" mechanism to activate the adsorbed N2, with GDY functioning as an electron reservoir and the V-TM pairs acting as electron transmitters, V-Cr@GDY and V-Fe@GDY exhibit high catalytic activity with low UL(NH3) values of -0.36 V and -0.42 V, respectively, and both DACs also effectively suppress the hydrogen evolution reaction, achieving nearly 100% theoretical faradaic efficiency for NH3 production. These findings underscore the critical role of electron transfer during the NRR and highlight the potential of V-containing DACs, and will inspire further experimental research in this interesting field.