SO2 adsorption properties of non-metal doped single-layer WSe2: A first-principles study

The threat posed by harmful gases such as sulfur dioxide (SO₂) to the environment and human health is growing increasingly severe, making developing highly efficient gas-sensing materials a critical research focus. This study employs first-principles density functional theory (DFT) to systematically investigate the role of silicon (Si) doping in the SO₂ adsorption process of single-layer WSe₂. The computational results indicate that Si doping significantly enhances the adsorption capacity of WSe₂ toward SO₂, with the adsorption energy increasing from -1.364 eV in intrinsic WSe₂ to -3.860 eV, suggesting that doping strengthens the interaction between the material and gas molecules. Further analysis shows that Si doping reduces the bandgap of WSe₂ from 1.599 eV to 1.092 eV. Despite the narrowing of the bandgap, the material retains its semiconductor properties. Following the adsorption of SO₂, a bandgap narrowing to 0.113 eV was observed, indicating an enhancement in the material’s sensitivity to gas response due to the synergistic effect of doping and gas adsorption. In the composite system with SO₂ adsorption, an increase in the work function of the material from 5.09 eV to 5.21 eV was recorded, suggesting an enhancement in the interfacial electric field due to the synergistic effect of doping and gas adsorption, thereby optimising electron transfer and gas recognition capabilities. Differential charge density analysis revealed that Si doping and SO₂ adsorption significantly induced interfacial charge transfer, improving gas recognition performance and electronic response. Optical performance analysis demonstrated that Si doping and SO₂ adsorption jointly improve the material’s optical absorption properties. The intensity of the central absorption peak following the adsorption of SO₂ by Si-doped WSe₂ has been shown to increase to 14.39 × 10⁴ cm⁻¹, representing a 2.1 % increase compared with the intrinsic system. The findings of this study provide a theoretical foundation for the design of high-performance gas sensors and optoelectronic devices, thereby opening new avenues for the regulation of the optoelectronic properties of two-dimensional materials.