The active site of Mδ+ tailed by B (or N)-doped graphyne for nitrogen reduction reaction through DFT study

Abstract

NN bond activation is one of the technical problems in the conversion of N₂-to-NH₃. In this work, we researched Cr, Mn, Co, Ni, Cu and Pt metal single atoms anchored on B/N-doped graphyne (M/X-GY) catalysts systematically by means of DFT. The results of Bader charge and charge density verified the charge transfers between single metal and the doped graphyne in M/X-GY catalysts. Cr (+1.001 e) and Mn (+0.800 e) exhibit higher positive valence, which is favorable for N₂ adsorption. Based on the "donation and back-donation" mechanism, the energies gaps of 5σ-N₂ and d-M for M=Cr, Mn and Co have the lower values of 3.01, 3.18, 3.18 eV, respectively, and the N₂ adsorption energies on Cr/GY (−2.046 eV) and Mn/GY (−1.622 eV) have the more negative values. As a result, the catalyst of Cr metal atom anchored on GY is promising candidate. The substitution of B can effectively promote the activation of N₂ and suppress the hydrogen evolution, while the substitution of N has the minimum ΔG_*N-NH of 0.26 eV and ΔG_NH3 of 0.08 eV. Compared with two different NRR pathways, the distal mechanism process is more preferential than the alternating pathway. The catalyst of Cr/N-GY has higher stability and can effectively activate N₂ to generate *N₂H, which can serves as promising catalysts throughout the NRR process.