Exploration of the Transition Metal-Doped CrS2 Monolayer as a Gas Sensor of Toxic Gases Based on the Density Functional Theory Method

In order to detect the harmful gases produced in the nonferrous metal smelting process, this study uses the transition metal atom (Fe, Co, Ni, and Cu)-doped CrS₂ (TM/CrS₂) monolayer as a sensing material to achieve high-sensitivity detection of CO, HCHO, NO, NO₂, and SO₂ gases. Density functional theory (DFT) calculations indicate that the TM/CrS₂ structure exhibits relative stability; the values of E_bind for the dopants on the CrS₂ substrate are noted as −4.565 eV for Fe/CrS₂, −4.187 eV for Co/CrS₂, −5.286 eV for Ni/CrS₂, and −3.695 eV for Cu/CrS₂. Additionally, the adsorption energies of all adsorption systems are less than −0.800 eV (except for SO₂-Cu/CrS₂), indicating chemical adsorption. Analysis of the band structure and density of states indicates that the electronic properties of the doped and adsorbed systems have undergone significant changes. Ni/CrS₂ and Co/CrS₂ exhibit high sensitivity (>10²) toward the five target gases (except for HCHO-Co/CrS₂), thus making them suitable as resistive-type sensors. The work function variations of the Fe/CrS₂ adsorption system exceed 5%, which can be used as a WF-based sensor. All of the above gases can be separated from TM/CrS₂ via temperature control. The results of this study demonstrate the gas-sensing potential of TM/CrS₂ monolayer materials.