Computational Investigation of Single-Atom Catalysts Anchored on Nitrogen-Doped Two-Dimensional NbSe₂ for Highly Selective CO₂ Reduction to Methane

The electrochemical CO2 reduction reaction (CO2RR) is a promising approach for CO2 emission reduction, but the development of efficient catalysts remains a major challenge. Here, a series of transition metal/nitrogen-doped NbSe2 (TM@N3-NbSe2) catalysts were selected to systematically investigate the reaction process and catalytic mechanism involved in the conversion of CO2 to methane (CH4) through density functional theory (DFT) calculations. The results indicate that CO2 has two possible adsorption configurations on TM@N3-NbSe2 surfaces, namely, physisorption and chemisorption. During the CO2 chemical adsorption process, a significant amount of charge is transferred from the substrate to CO2, thereby activating the formation of CO2 into a bent structure. In contrast, physically adsorbed CO2 cannot accept electrons from the substrate, resulting in minimal interaction between CO2 and the TM@N3-NbSe2. According to the reaction pathway and limiting potentials, the catalytic activity of TM@N3-NbSe2 for CO2-to-CH4 conversion can be ranked in the following order: Co > Ir > Pd > Cu > Os > Fe > Rh > Pt > Ag > Ru > Ni > Au. Among them, Co@N3-NbSe2 exhibited more prominent catalytic properties, and the free energy change required to be overcome during the conversion of CO2 to CH4 is only 0.22 eV. Most TM@N3-NbSe2 systems exhibit higher selectivity for the CO2RR compared to the hydrogen evolution reaction, making them promising candidates as CO2RR catalysts. This study reveals the mechanism of transition metal and nitrogen codoped two-dimensional materials in CO2RR, which will help to screen high-efficiency catalysts to improve efficiency and selectivity.