DFT Insights into the Gas Sensing Behavior of Platinum Group Metal Doped MoSe₂ Monolayers

Since the 1970s, hydrogen has been recognized as a clean fuel, but it is highly flammable and often found with toxic gases like H₂S and HCN during production and storage. Reliable detection is essential to prevent accidents and ensure safer processes, given its small size, high diffusivity, and invisibility. Using density functional theory, we examined the substitutional doping of a Se atom in the MoSe₂ monolayer with Pt, Ir, Os, Ru, Rh, and Pd atoms, which enhances charge transfer and sensitivity to H₂, H₂S, and HCN gases. A thorough analysis was conducted on adsorption energy, band structure, density of states, charge transfer, work function, sensitivity, and recovery times. Our results show that doping increases charge transfer and adsorption compared to the pure monolayer. The Os-MoSe₂ monolayer exhibits greater adsorption for H₂ gas. All doped monolayers exhibit strong adsorption of H₂S gas (more than -0.7 eV), with recovery at elevated temperatures and high sensitivity. The Pt- and Pd-MoSe₂ monolayers recover in 129.3 and 12.7 seconds, respectively, after chemisorption with HCN gas, demonstrating reusability at room temperature. Our findings provide valuable insights for designing effective gas sensors, enhancing industrial safety, and supporting clean energy technologies.