Cu- and Al-Decorated Monolayer TiSe₂ for Enhanced Gas Detection Sensitivity: A DFT Study

The rapid industrial development has contributed to worsening global pollution, necessitating the urgent development of highly sensitive, cost-effective, and portable gas sensors. In this work, the adsorption of CO, CO₂, H₂S, NH₃, NO, NO₂, O₂, and SO₂ gas molecules on pristine and Cu- and Al-decorated monolayer TiSe₂ has been investigated based on first-principles calculations. First, the results of the phonon spectrum and ab initio molecular dynamics simulations demonstrated that TiSe₂ is dynamically stable. In addition, compared to pristine TiSe₂ (-0.029 to -0.154 eV), the adsorption energy of gas molecules (excluding CO₂) significantly decreased after decorated with Cu or Al (-0.212 to -0.977 eV in Cu-decorated TiSe₂, -0.438 to -2.896 eV in Al-decorated TiSe₂). Among them, NH₃ and NO₂ have the lowest adsorption energies in Cu and Al-decorated TiSe₂, respectively. Further research has shown that the decrease in adsorption energy of gas molecules is mainly due to orbital hybridization and charge transfer between decorated Cu and Al atoms and gas molecules. These findings suggest that TiSe₂ decorated with Cu and Al can effectively improve its sensitivity to NH₃ and NO₂, respectively, making it promising in gas sensing applications.