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.