Gas-Sensing Properties of Two-Dimensional Phosphorus Materials toward Decomposition Products of SF6

Sulfur hexafluoride (SF6) can be decomposed under electrical or thermal stress in gas-insulated switchgear (GIS), and the resulting byproducts pose safety risks and provide diagnostic signals. In this work, density-functional-theory calculations were used to evaluate gas-sensing descriptors for six representative molecules (SO2, H2S, SO2F2, SOF2, SF6, and H2O) on three phosphorene allotropes (BP, Blue_P, and VP) and on four alloyed α-AsxP1-x monolayers (x = 0.25, 0.50, 0.75, and 1.00). Adsorption energy (Eads), adsorption distance, Bader charge transfer, projected density of states, work-function shifts, and recovery time were analyzed to compare sensitivity, selectivity, and recoverability. Across the pristine phosphorene allotropes, SO2 is consistently the most strongly adsorbed species, while Blue_P shows a narrow energetic separation between decomposition products and intact SF6, implying limited adsorption-energy-based selectivity in an SF6 background. The increase of As composition in the α-AsxP1-x alloys strengthens the interaction with key byproducts (especially SO2 and SOF2) while maintaining a weak response to SF6 and H2O, which is favorable for online GIS monitoring under humidity interference. In addition, biaxial strain provides an effective, reversible knob to tune band edges and adsorption-driven charge transfer without changing surface chemistry.