Gas-sensing performance of TM(V, Ti, Ni)@GaN monolayers for transformer oil dissolved gas detection: A DFT study

This study systematically investigates the gas-sensing performance of transition-metal-doped GaN monolayers (TM = V, Ti, Ni) toward five typical dissolved gases in transformer oil (CO, H₂, CH₄, C₂H₂, C₂H₄) using first-principles density functional theory (DFT). Adsorption energy, charge transfer, electronic structure modulation, recovery time, and work function sensitivity were comprehensively analyzed. Results show that TM doping significantly enhances the interaction strength and electronic response of GaN, with Ti@GaN exhibiting the most favorable stability and sensitivity. Specifically, Ti@GaN demonstrates the highest work function sensitivity to H₂ (34.19 %) and C₂H₂ (21.57 %), strong adsorption energies for CO (−2.27 eV), C₂H₂ (−2.89 eV), and C₂H₄ (−2.09 eV), and rapid recovery characteristics (0.576 s for CO at 500 K). Moreover, competitive adsorption analysis reveals robust selectivity, with H₂ and C₂H₂ effectively blocking interference from CO and CH₄. These results identify Ti@GaN as the most promising candidate for fabricating high-performance sensors dedicated to transformer fault gas detection.