Decreased spin-resolved anti-bonding states filling to accelerate CHO conversion into CH2O in transitional metal-doped Mo2C monolayers during CO2 reduction

Abstract

CO₂ reduction reactions (CO₂RRs) are considered as one of the most potential strategies to realize the effective capture and conversion of CO₂, which can not only reduce the globally accelerating CO₂ emission but also generate high-value-added products. In this study, the electronic structure of transition metal atom-doped Mo₂C (TM-Mo₂C), CO₂ adsorption, activation and the performance for CO₂ reduction into CH₄ were investigated by density functional theory. Spontaneously CO₂ capture and activation abilities were observed in TM-Mo₂C electrocatalysts due to the enhanced interaction between CO₂ and Mo-3d/TM-3d orbitals. TM doping can increase the interaction between CHOH/CH₂O and active sites, and decrease spin up and down integrated-crystal orbital Hamilton population (ICOHP_spinup and ICOHP_spindown). Thus, TM doping promotes the adsorption of CHOH/CH₂O and decreases the Gibbs free energies of *CHO → *CHOH (ΔG_*CHO→*CHOH) and *CHO → *CH₂O (ΔG_*CHO→*CH2O) reaction steps, in which ΔG_*CHO→*CH2O of Co/Cu/Cr/Mn/Ni-Mo₂C has a linear relationship with ICOHP_spinup and ICOHP_spindown. Moreover, the limiting potentials (U_L) are −0.58, −0.69, −0.38, −0.67, and −0.61 for Co/Cu/Cr/Mn/Ni-Mo₂C, respectively, which are not only more positive than that of pure Mo₂C (U_L = −1.35 eV) but also equal to or more positive than that of the reported Cu (−0.81 and −0.60 eV) catalyst. Our present results provide not only reference for the enhanced CO₂RR performance of Mo₂C with TM doping but also primary insights into the relationship between the spin up/down anti-bonding states filling and the reaction rate of CHO conversion into CH₂O.