A comprehensive first-principles investigation on enhancing toxic gases adsorption performance by platinum group metal-doped MoSe₂ monolayer

Two-dimensional MoSe₂ is a promising gas-sensing material, but its inert surface limits adsorption capacity. Via first-principles calculations, this study shows that doping MoSe₂ with platinum group metals (Ru, Rh, Pd) induces chemisorption, significantly enhancing adsorption of CO, H₂S, and SO₂. Hybridization of the doped metals' 4d orbitals with Mo-4d and Se-2p orbitals introduces local electronic states near the Fermi level, reducing the band gap from the pristine 1.447 eV to 0.317 eV in the Ru-MoSe₂ system. This enhances conductivity and promotes charge transfer from the doped metal as an electron donor to gas molecules as electron acceptors, with Ru-MoSe₂ adsorbing CO showing the highest charge transfer. The formation of covalent bonds (e.g., C-Ru, S-Rh) converts weak physisorption to strong chemisorption, with adsorption capacity following Ru > Rh > Pd, related to dopants' electronegativity and orbital overlap strength. Doping synergistically enhances adsorbate-material interaction by introducing active sites and regulating electronic structure, enabling more stable adsorption and higher charge transfer efficiency. At 798 K, Ru-MoSe₂ adsorbing CO has a recovery time of only 4 seconds; Rh-MoSe₂ enables room-temperature detection of H₂S/SO₂. This study confirms doped MoSe₂ as a tunable platform for high-performance gas sensing, balancing sensitivity and desorption via atomic-level electronic engineering.