From Adsorption to Finite-Bias Transport: Pd-Decorated GeS Monolayer for Sensing SF6 Decomposition Gases

Abstract

Reliable detection of sulfur hexafluoride (SF6) decomposition products is important for condition monitoring in gas-insulated switchgear. Here, density functional theory and nonequilibrium Green’s function calculations are combined to connect molecular adsorption on atomically thin Pd-decorated GeS with the finite-bias current of a nanoscale two-probe device. Pd binds strongly to GeS (−3.40 eV) and forms an active center for H2S, SO2, SOF2, and SO2F2, whose adsorption energies span −1.32 to −0.46 eV. The strongest adsorption, largest Mulliken charge transfer, and largest band-gap modulation occur for different adsorbates, showing that no single equilibrium descriptor determines the electrical readout. Finite-bias calculations instead reveal molecule-specific transmission and signed current changes whose magnitude and direction depend on the applied voltage. Within the idealized single-molecule, fixed-coverage model considered here, these results establish a mechanistic adsorption-to-transport connection and identify bias selection as an additional degree of freedom for differentiating SF6 decomposition products on a two-dimensional sensing interface.