First-Principles Study of Au-Doped InN Monolayer as Adsorbent and Gas Sensing Material for SF₆ Decomposed Species

As an insulating medium, sulfur hexafluoride (SF₆) is extensively applied to electrical insulation equipment to ensure its normal operation. However, both partial discharge and overheating may cause SF₆ to decompose, and then the insulation strength of electrical equipment will be reduced. The adsorption properties and sensing mechanisms of four SF₆ decomposed components (HF, SO₂, SOF₂ and SO₂F₂) upon an Au-modified InN (Au-InN) monolayer were studied in this work based on first-principles theory. Meanwhile, the adsorption energy (E_ad), charge transfer (Q_T), deformation charge density (DCD), density of states (DOS), frontier molecular orbital and recovery property were calculated. It can be observed that the structures of the SO₂, SOF₂ and SO₂F₂ molecules changed significantly after being adsorbed. Meanwhile, the E_ad and Q_T of these three adsorption systems are relatively large, while that of the HF adsorption system is the opposite. These phenomena indicate that Au-InN monolayer has strong adsorption capacity for SO₂, SOF₂ and SO₂F₂, and the adsorption can be identified as chemisorption. In addition, through the analysis of frontier molecular orbital, it is found that the conductivity of Au-InN changed significantly after adsorbing SO₂, SOF₂ and SO₂F₂. Combined with the analysis of the recovery properties, since the recovery time of SO₂ and SO₂F₂ removal from Au-InN monolayer is still very long at 418 K, Au-InN is more suitable as a scavenger for these two gases rather than as a gas sensor. Since the recovery time of the SOF₂ adsorption system is short at 418 K, and the conductivity of the system before and after adsorption changes significantly, Au-InN is an ideal SOF₂ gas-sensing material. These results show that Au-InN has broad application prospects as an SO₂, SOF₂ and SO₂F₂ scavenger and as a resistive SOF₂ sensor, which is of extraordinary meaning to ensure the safe operation of power systems. Our calculations can offer a theoretical basis for further exploration of gas adsorbent and resistive sensors prepared by Au-InN.