First-principles analysis of the impacts of transition metal doping on the adsorption of light hydrocarbon molecules on MoSe2 monolayers.

CONTEXT: Monolayer MoSe2 is a promising material for gas sensing; however, its weak interactions with nonpolar light hydrocarbons inherently limit its sensitivity and selectivity. In this study, first-principle calculations were employed to elucidate how substitutional transition-metal substitution regulates the adsorption of CH4, C2H4, and C2H6 on MoSe2. The incorporation of V, Cr, Mn, Fe, Co, and Ni introduces dopant-specific d-derived states near the Fermi level, thereby reconstructing the local electronic structure and modulating adsorbate-surface coupling. Across the investigated systems, the adsorption strength follows the order C2H4 (-0.67 to -0.98 eV) > C2H6 (-0.34 to -0.58 eV) > CH4 (-0.24 to -0.42 eV), with corresponding charge-transfer ranges of 0.14-0.20, 0.08-0.12, and 0.04-0.07 e, respectively. The substantially stronger interaction with C2H4 originates from π-d hybridization, whereas saturated σ bonding framework of CH4 and C2H6 limits orbital overlap with the dopant-derived states. These results establish a direct relationship between dopant-induced electronic states and hydrocarbon adsorption, providing a theoretical basis for the rational design of MoSe2-based sensors with improved sensitivity toward hydrocarbons. METHODS: DFT calculations were performed using Quantum ESPRESSO with a PBE + U plane-wave framework and a 450 eV cutoff. A 4 × 4 × 1 MoSe2 supercell with a 30 Å vacuum layer and a 7 × 7 × 1 Monkhorst-Pack grid was used. Substitutional V, Cr, Mn, Fe, Co, and Ni dopants were introduced at Mo sites and all atomic structures were optimized using the Broyden-Fletcher-Goldfarb-Shanno algorithm; long-range dispersion interactions were described using the Grimme DFT-D3 correction. The adsorption energies, Hirshfeld charge transfer, electronic density of states, band structure, and thermally activated recovery time were subsequently evaluated.