Study on highly selective NO2 gas sensors based on (Fe, Mo)-doped monolayer WSe2

The two-dimensional (2D) material WSe₂ is frequently employed in gas sensors due to its excellent electrical properties. However, the weak interaction between the pristine WSe₂ and gas molecules limits its application. Therefore, in this paper, the adsorption behavior of transition metal X (X = Fe, Mo) atom-doped monolayers WSe₂ on H and O atoms and molecules of NO₂, HCN, and CO gases is investigated to gain insights into the physical mechanisms of adsorbent-substrate interactions. Doping significantly improves the adsorption properties between the substrate and the gas molecules, with the best adsorption showing for NO₂ gas molecules and O atoms. The relationship between transition metals and the improvement of adsorption performance is explored by the center position of transition metal d orbitals in different systems, and it is found that the higher the center position of the transition metal d band, the stronger the adsorption between adsorbent and substrate. Compared to pristine WSe₂, Mo atom doping in the transition metal doped system has higher adsorption sensitivity to gas molecules and exhibits highly selective adsorption and chemisorption behaviors through high adsorption energies and electron transfer to NO₂ molecules. It is demonstrated that X (X = Fe, Mo) doped WSe₂ can be used as a gas-sensitive material for efficient gas detection.