Low‐Valence Metal Single Atoms on Graphdiyne Promotes Electrochemical Nitrogen Reduction via M‐to‐N2 π‐Backdonation

Abstract

AbstractThe M‐to‐N2 π‐backdonation weakens the triple bond of N2 and shall promote the sluggish electrochemical nitrogen reduction reaction (ENRR). By using weak σ‐ and π‐donating graphdiyne (GDY) as a supporting material, herein, a versatile approach is described to stabilize low‐valence metal single atoms (SA) on GDY (M SA/GDY; M = Cr, Mo, W, Mn, and Re). Under the rigorous ENRR protocol, an activity trend of Re SA/GDY > Mo SA/GDY > Cr SA/GDY > W SA/GDY >> Mn SA/GDY (no activity) is delivered. Theoretical calculations reveal that the strong M‐to‐N2 π‐backdonation of Re SA/GDY renders a low energy requirement of +0.39 eV for the reductive hydrogenation of *N2 to *NNH, which is considered as the bottleneck of ENRR. A novel NH3 desorption mechanism through N2 or H2O aided ligand exchange mechanism is proposed to facilitate the NH3 desorption from Re SA/GDY with a low energy input of +0.83 eV for the distal and mix pathways. This study expands the scope of low‐valance SA with boosted π‐backdonation capacity and offers new mechanistic insights for ENRR.