The 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.
In
contrast to the energy-extensive Haber–Bosch process,
green production of ammonia (NH3) at ambient conditions
remains as one of the main goals of the 21st century. In this work,
we systematically studied single and double transition metal atoms
(Fe, Co, Mo, Ru) anchored on graphyne (GY) for nitrogen (N2) reduction by means of density functional theory (DFT). We demonstrated
that Ru dimer anchored on two-dimensional (2D) GY exhibits superior
catalytic activity for nitrogen reduction via an enzymatic pathway
with the maximum free energy change (ΔG) of
0.43 eV. Our findings propose highly reactive catalytic materials
for efficient N2 reduction while highlighting the importance
of double-atom catalysts for nitrogen reduction reaction (NRR).
Critically, the central metal atoms along with their coordination environment play a significant role in the catalytic performance of single-atom catalysts (SACs). Herein, 12 single Fe, Mo, and Ru atoms supported on defective graphene are theoretically deigned for investigation of their structural and electronic properties and catalytic nitrogen reduction reaction (NRR) performance using first-principles calculations. Our results reveal that graphene with vacancies can be an ideal anchoring site for stabilizing isolated metal atoms owing to the strong metal−support interaction, forming stable TMC x or TMN x active centers (x = 3 or 4). Six SACs are screened as promising NRR catalyst candidates with excellent activity and selectivity during NRR, and RuN 3 is identified as the optimal one with an overpotential of ≥0.10 V via the distal mechanism.
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