Mechanism of regulating frontier d-orbital configuration and efficient CO adsorption via single-atom Ta anchored on a MoS2 substrate

The specific recognition and high-performance adsorption of pollutant gas molecules represent a central objective in the research of two-dimensional MoS 2 -based gas sensing materials; however, the intrinsic inertness of the pristine MoS 2 basal plane—resulting from the shielding of d-electron orbitals within the closed hexagonal lattice of S atoms—poses a fundamental limitation, while single-atom catalysts, known for their high atomic utilization efficiency and unsaturated electronic modulation capability, offer an effective strategy to activate such inert surfaces. Based on density functional theory, this study establishes a theoretical model involving Ta transition metal atoms anchored at various sites on the MoS 2 surface to catalyze CO adsorption, thereby elucidating the mechanism by which single Ta atoms activate the electronic orbitals of MoS 2 via unsaturated coordination. The distinct coordination environments of Ta atoms lead to the formation of multiple non-degenerate localized d-orbital states, and the extent of energy level matching between these orbitals and the molecular orbitals of CO significantly influences the adsorption properties. The results demonstrate that different Ta doping sites on the MoS 2 substrate produce distinct local d-orbital configurations, resulting in varying CO adsorption energies, selectivity, and desorption times. This work thus focuses on how Ta single atoms anchored at different sites facilitate the transition from physisorption to chemisorption of CO molecules, wherein the adsorption strength is determined by the degree of energy level coupling between the spatial configuration of the frontier d-orbitals and the HOMO or LUMO orbitals of CO. Overall, these findings provides novel insights into the sensing and detection of CO molecules on MoS 2 -based materials by investigating the coupling between the frontier d-orbital configurations at various doping sites and the energy-level alignment of gas molecular orbitals. • Single-atom Ta doping at different sites activates the inert basal plane of MoS 2 . • The d-orbital configuration of Ta-modified MoS 2 aligns with the energy levels of the CO molecular orbitals. • Modulating the d-orbital configuration enables the transition from physisorption to chemisorption of CO.