Density Functional Theory Study of Metal-Cluster-Modified Indium Selenide Monolayers for Transformer Oil Gas Sensing

Real-time detection of characteristic dissolved gases, specifically CO, H₂, C₂H₂, and C₂H₄, serves as a fundamental strategy for the early diagnosis of latent faults and comprehensive health assessment of oil-immersed power equipment. To address this industrial necessity, first-principles investigations based on density functional theory (DFT) were performed to evaluate the gas-trapping capabilities and sensing efficacies of InSe monolayers functionalized with Ag₃, Cu₃, and Ni₃ clusters. To achieve a profound understanding of the interfacial interaction mechanisms and gas-sensing performance, a comprehensive assessment of crucial physicochemical parameters was conducted, which encompassed optimized binding configurations, adsorption energies, band gaps (E_g), differential charge densities (DCD), charge-transfer amounts (Q_T), density of states (DOS), partial density of states (PDOS), frontier molecular orbitals, desorption times, and theoretical sensitivities. Our findings demonstrate that introducing metal clusters remarkably strengthens the interactions between the substrate and the target gases, endowing the functionalized monolayers with a vastly superior gas capture efficiency relative to that of bare InSe. Theoretical kinetic evaluations proved that the Ag₃-decorated InSe configuration enables the efficient desorption of CO (5.42 s at 348 K), C₂H₄ (8.83 s at 398 K), and C₂H₂ (2.89 s at 398 K) under mild thermal conditions. Similarly, the Cu₃-InSe platform facilitated the release of CO (1.221 s at 398 K) within comparable temperature ranges. In contrast, H₂ exhibits only weak physisorption on Ag₃-InSe, Cu₃-InSe, and Ni₃-InSe, with low adsorption energies and negligible perturbation to the electronic structure, indicating that these materials are not suitable for H₂ sensing. Conversely, the Ni₃-InSe complex exhibited overwhelmingly potent binding strength, retaining a rigid grip on CO, C₂H₄, and C₂H₂ across temperatures spanning from 298 to 498 K. Such distinct behaviors suggest that while Ag₃-InSe and Cu₃-InSe are highly promising for active sensor designs, Ni₃-InSe serves as an ideal candidate for industrial gas scavenging.