SF6 Decomposition Gas Sensing on an AlN/Janus MoSeTe Heterostructure: A Density Functional Theory Study.

The detection of SF6 decomposition gases is crucial for condition monitoring and fault diagnosis of gas-insulated electrical equipment. In this work, a van der Waals heterostructure composed of an AlN monolayer and Janus MoSeTe (AlN@MoSeTe) is proposed as a sensing platform for representative SF6 decomposition gases, including SO2, H2S, SOF2, SO2F2, and SF4. Density functional theory calculations were performed to systematically investigate adsorption characteristics, electronic structure modulation, and sensing-related properties of the heterostructure. The results reveal that AlN@MoSeTe exhibits differentiated responses toward various gas species. SO2, SOF2, and SF4 induce effective adsorption accompanied by pronounced charge redistribution and density-of-states modulation, whereas H2S and SO2F2 cause only minor electronic perturbations. Notably, SOF2 and SF4 demonstrate favorable response-recovery characteristics. The calculated desorption time of SOF2 is approximately 9.93 s at 358 K, while SF4 exhibits a desorption time of about 13.6 s at 598 K, indicating controllable reversibility under experimentally accessible temperature conditions. In contrast, the excessively strong adsorption of SO2 limits its recovery behavior. The sensing mechanism is attributed to adsorption-induced charge transfer, surface oxygen ion interactions, and modulation of the electron depletion layer in the n-type AlN@MoSeTe heterostructure. These findings highlight AlN@MoSeTe as a promising candidate for the selective detection of SF6 decomposition gases, particularly SOF2 and SF4, and provide theoretical insight for the rational design of advanced gas sensors for power equipment monitoring.