Comparative Study on Sensing Properties of the PdSe ₂ –CdS Heterojunction and Pd-Modified PdSe ₂ –CdS for Dissolved Gases in Transformer Oil Based on Density Functional Theory Calculations

The detection of dissolved gases in transformer oil is critical for the early identification and prevention of faults, thereby improving the operational safety of power systems. This work systematically investigates the adsorption interactions between the PdSe 2 –CdS heterojunction/PdSe 2 –CdS modified by Pd (Pd-PdSe 2 –CdS) and multiple dissolved gas molecules (H 2, CH 4, C 2 H 2, CO, C 2 H 4, C 2 H 6 ) in transformer oil, employing comprehensive first-principles density functional theory (DFT) calculations. Among these two novel two-dimensional sensing materials, the gas-sensing response characteristics of Pd-PdSe 2 –CdS are significantly superior to those of the PdSe 2 –CdS heterostructure. Pd-PdSe 2 –CdS exhibits not only excellent adsorption performance for CO but also a favorable recovery time, with a recovery time of 108.54 s at 298 K. However, the desorption time shortens significantly as the temperature rises to 398 K. Pd-PdSe 2 –CdS can act as a heated sensor for CO in transformer oil. These insights offer valuable theoretical underpinnings for the design of advanced gas sensors suitable for real-time condition monitoring in electrical equipment.