Anionic and Cationic Doped TiO2 Surfaces for Phosgene Oxime Detection

The adsorption of the phosgene oxime (CX) molecule from different orientations on the pure (111) TiO₂ surface was studied using periodic DFT calculations. Adsorption energies are negative in all configurations, indicating the formation of stable adsorption systems. However, further analysis focused on the adsorption of the CX via its N atom on the surface, which exhibited the highest adsorption energy. Furthermore, the total density of states and HOMO–LUMO calculations were performed to investigate the effect of the CX adsorption on the electronic properties of the pure and doped (111) TiO₂ surfaces. It should be noted that the (Zr⁺⁴–S⁻²) and Ge⁺⁴ doped (111) TiO₂ surfaces have the highest and lowest adsorption energy with the values of − 85.92 and − 19.39 kcal/mol, respectively, compared to the other doped adsorption systems. Nevertheless, the (Ge⁺⁴) adsorption system exhibits the largest variation in band gap energy (2.20 and 2.73 eV for the Ge- adsorption system and Ge-surface, respectively ∼20% change) during CX adsorption, indicating the highest change in its electrical conductivity. Consequently, the Ge⁺⁴-doped adsorption system is a promising sensor of toxic CX molecule.