A DFT Investigation of SF6 Decomposition Products Adsorption on V-doped Graphene/MoS2 Heterostructures

The detection of SF₆ decomposition products is essential for diagnosing insulation faults in gas-insulated switchgear. Using first-principles density functional theory, this study investigates the adsorption behavior of five characteristic gases (H₂S, SO₂, SOF₂, SO₂F₂, and SF₆) on pristine and vanadium-doped graphene/MoS₂ (GMV) heterostructures to evaluate their potential for gas sensing applications. Pristine graphene/MoS₂ exhibits weak physisorption toward all target molecules, with low adsorption energies and negligible charge transfer, indicating insufficient sensitivity for practical use. To address this limitation, a V-doped graphene/MoS₂ heterostructure is proposed, wherein vanadium atoms are incorporated into the graphene lattice to introduce active centers and modulate interfacial charge transfer. The results demonstrate that H₂S, SO₂, and SOF₂ preferentially adsorb atop the V site via local covalent interactions, with significantly enhanced adsorption energies (up to −0.388 eV for SO₂) and shortened distances. In contrast, SO₂F₂ and SF₆ adsorb near electron-depleted carbon regions driven by electrostatic attraction. Charge density difference and Bader charge analyses reveal pronounced charge redistribution upon SO₂ and SF₆ adsorption, while density of states analysis confirms orbital hybridization near the Fermi level, suggesting possible chemical bond formation. Notably, adsorption of SO₂ and SF₆ substantially reduces the density of states at near Fermi level, indicating a measurable modulation of surface conductivity. These findings establish V-doped graphene/MoS₂ as a promising sensing material for selective detection of SF₆ decomposition products, offering a viable strategy for advancing online monitoring technologies in power systems.