Theoretical Study on Gas-Sensing Mechanisms of Transition Metal-Doped MoS₂ for Transformer Oil Dissolved Gases

Oil-immersed transformers are essential components in power transmission and distribution systems, and their insulation performance and operation status are closely related to the changes of dissolved gases in the internal oil. The use of high-performance gas-sensitive materials to realize online detection of dissolved gases in the oil is of great significance to enhance the reliability of equipment operation and fault detection. In this work, the adsorption behavior and sensing performance of four typical dissolved gases in transformer oil (H₂, CH₄, C₂H₂, C₂H₄) on the surface of MoS₂ doped with different transition metals (Cu, Ni, Ta, Ti) are systematically investigated based on the density functional theory (DFT). First, the analysis yielded poor sensing properties of pristine MoS₂ for four gas molecules. Then the most stable doping structure of TM-MoS₂ is selected, and based on this stable configuration, the adsorption structure was constructed and optimized. Comparative analysis of the structure, adsorption energy, charge transfer, density of states and work function parameters of TM-MoS₂ after adsorption of gas molecules showed that doping with transition metals can improve the adsorption and sensing properties of the material. Finally, the recovery time and sensitivity were investigated, and the results showed that Cu-MoS₂ exhibited suitable recovery time and high sensitivity in detecting C₂H₂ and C₂H₄, Ta-MoS₂ for CH₄ and Ti-MoS₂ for H₂. This work provides theoretical guidance for the potential application of transition metal-doped MoS₂ as a gas-sensitive material in transformer fault gas detection.