Regulating the coordination environment through doping N atoms for single-atom Mn electrocatalyst of N2 reduction with high catalytic activity and selectivity: A theoretical study

Abstract

Electrochemical N2 reduction reaction (NRR) is a promising way for ammonia synthesis, and developing novel electrocatalyst with high catalytic activity and selectivity is an urgent matter. Herein, the catalytic performances of single-atom Mn catalysts supported with nitrogen-doped graphene substrates (MnSA@Vx-Ny, x = s, d. y = 0, 1, 2, 3, 4.) for NRR have systematically investigated through density functional theory (DFT) calculations. The catalytic activity and selectivity of MnSA@Vx-Ny were discussed through reaction path, Gibbs free energy variation, hydrogen evolution reaction (HER), electron transfer and projected density of states. The result reveals the adsorption energy of N2 and catalytic activity of MnSA@Vx-Ny were effectively regulated through modulating the coordination environment of Mn atom. MnSA@Vs-N1 has the highest catalytic activity and selectivity among all studied catalysts for NRR at room temperature. MnSA@Vs-N1 can facilitate NRR by the distal mechanism, and the potential determining step is *N2 + H++ e− → *NNH with a free energy variation of 0.77 eV. Simultaneously, HER is suppressed by the high selectivity of N2 adsorption on MnSA@Vs-N1. This adjusting method can provide a guideline for developing robust electrocatalyst for NRR.