Adsorption and Sensing Mechanisms of Transformer Dissolved Gases on Transition Metal-Doped MoTe ₂ Monolayers: A DFT Study

Oil-immersed transformers are essential components for voltage transformation and energy delivery within power systems, with their operating condition having a direct influence on the reliability and stability of the grid. During prolonged operation, multiple stresses─electrical, thermal, and mechanical─gradually degrade insulating oil and solid insulating materials, generating dissolved gases (H₂, CH₄, C₂H₂, C₂H₄). Monitoring the types and concentrations of these characteristic gases enables timely identification and condition evaluation of internal faults in transformers. MoTe₂ shows broad application prospects in gas sensing. However, its intrinsic structure exhibits limited adsorption capacity for these four gas molecules. To enhance its sensing performance, this work systematically explored how transition metal (Au, Ir, Pd, Ti) doping influences the properties of single-layer MoTe₂ in detecting transformer fault characteristic gases, using first-principles density functional theory (DFT). Structural stability was evaluated through binding energy calculations, while adsorption mechanisms were analyzed using adsorption energy, charge transfer, and density of states (DOS) studies. The findings reveal that introducing metal dopants markedly improves MoTe₂'s ability to adsorb and its electronic response characteristics toward gas molecules. Specifically, Au-MoTe₂ exhibited recovery times of 0.44 and 2.15 s for detecting C₂H₂ and C₂H₄, respectively, and demonstrated a significant bandgap modulation effect, while Ti-MoTe₂ exhibited substantial bandgap shifts (-18.9% and -462.21%) during H₂ and CH₄ detection, demonstrating high sensitivity and responsiveness. All demonstrate tremendous potential as gas-sensitive materials for their respective gases. This work elucidates the modulation mechanism of transition metal doping in MoTe₂, providing theoretical guidance for designing high-performance materials for dissolved gas detection in transformer oil.