Pt-Doped HfS₂ Monolayer as a Novel Sensor and Scavenger for Dissolved Gases (H₂, CO₂, CH₄, and C₂H₂) in Transformer Oil: A Density Functional Theory Study

Detecting the types and concentrations of dissolved gases in insulating oil by resistivity-type sensors is an extremely effective means for diagnosing faults in an oil-immersed transformer. However, further breakthroughs and innovations are needed in gas-sensitive materials for preparing high-performance resistivity-type sensors. In this investigation, the application possibility of using Pt-doped HfS₂ (Pt-HfS₂) as gas-sensitive materials for the detection of dissolved H₂, CO₂, CH₄, and C₂H₂ in oil has been verified by analyzing the adsorption energy (E_ad), differential charge density (DCD), density of states (DOS), frontier molecular orbital, and desorption time based on density functional theory (DFT). The outcomes suggest that the band gap of HfS₂ is obviously narrowed after doping Pt at the position of the bridge between the S and Hf atoms, resulting in a significant increase in the conductivity of HfS₂. The low adsorption energy implies that there is only weak physical adsorption between Pt-HfS₂ and CO₂ (-0.783 eV). In contrast, the highly hybridized atomic orbitals of Pt with H₂, CH₄, and C₂H₂ indicate that strong chemical adsorption reactions occur. Two-dimensional Pt-HfS₂ as a gas sensor has a great monitoring performance for CH₄ at 298 K (room temperature). This research serves as theoretical guidelines for probing the application potential of Pt-HfS₂ in fault diagnosis and predictive maintenance of an oil-immersed transformer.