关键词: 电化学氮还原, 过渡金属掺杂氮碳材料, 密度泛函理论, 从头算动力学

Currently, the electrocatalytic nitrogen reduction reaction (NRR) is a significant catalytic process under ambient conditions. For the N₂ fixation reaction, the metal-based catalysts are the most widely explored catalysts, but compared to the traditional Haber-Bosch process, the poor resistance and low selectivity to acids or bases, and the low Faradaic efficiency, production rate, and stability of metal-based catalysts, make them uncompetitive with industrial N₂ fixation. During these years, inspired by applications of carbon material catalysts for electrocatalytic field, the carbon material catalysts have attracted great attention, especially for transition-metal-doped carbon material catalysts. In this work, to obtain insight into the influence of water ambient condition on the catalytic performance of transition-metal-doped carbon material catalyst for electrochemical NRR, and to screen out the optimal catalyst structure with excellent catalytic performance, herein, under actual ambient conditions, we systematically described the thermodynamic stability and catalytic performance of a series of transition-metal-doped carbon material catalysts (TMN_xC_y, TM=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, x=1~4, y=4–x, 40 models) for NRR by means of density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. To simulate water condition during the NRR, we employed a mixed implicit+explicit solvation model, in which explicit water molecules are included in the first solvation shell, forming hydrogen bonds with the intermediate adsorbates of NRR, and an implicit solvent model captured longer-range solvation effects. The calculation results indicate that the 40 catalysts possess high thermodynamic stability, even at 700 K, and can be used as potential catalysts toward ammonia synthesis. It is noted that VN₃C₁ catalyst exhibits the best performance via a NRR enzymatic pathway under the actual water ambient condition with a mixed implicit+explicit solvation model, which has a lowest change value of free energy of 0.35 eV (at U=0 V vs. RHE) for potential-determining step. These results may reveal a new perspective for artificial ammonia synthesis using a single-atom catalyst under actual ambient conditions.

Key words: electrochemical nitrogen reduction reaction, transition-metal-doped carbon material, DFT, AIMD