Computational Investigation of Single-Atom Catalysts Anchored on Nitrogen-Doped Two-Dimensional NbSe for Highly Selective CO Reduction to Methane.

The electrochemical CO reduction reaction (CORR) is a promising approach for CO emission reduction, but the development of efficient catalysts remains a major challenge. Here, a series of transition metal/nitrogen-doped NbSe (TM@N-NbSe) catalysts were selected to systematically investigate the reaction process and catalytic mechanism involved in the conversion of CO to methane (CH) through density functional theory (DFT) calculations. The results indicate that CO has two possible adsorption configurations on TM@N-NbSe surfaces, namely, physisorption and chemisorption. During the CO chemical adsorption process, a significant amount of charge is transferred from the substrate to CO, thereby activating the formation of CO into a bent structure. In contrast, physically adsorbed CO cannot accept electrons from the substrate, resulting in minimal interaction between CO and the TM@N-NbSe. According to the reaction pathway and limiting potentials, the catalytic activity of TM@N-NbSe for CO-to-CH conversion can be ranked in the following order: Co > Ir > Pd > Cu > Os > Fe > Rh > Pt > Ag > Ru > Ni > Au. Among them, Co@N-NbSe exhibited more prominent catalytic properties, and the free energy change required to be overcome during the conversion of CO to CH is only 0.22 eV. Most TM@N-NbSe systems exhibit higher selectivity for the CORR compared to the hydrogen evolution reaction, making them promising candidates as CORR catalysts. This study reveals the mechanism of transition metal and nitrogen codoped two-dimensional materials in CORR, which will help to screen high-efficiency catalysts to improve efficiency and selectivity.