Eye-readable gasochromic and electrical detectability of hydrogenated Pd-TiO2 to gaseous fluorine species

Highlights: • A hydrogenated Pd-TiO₂ nanohybrid has multimodal gaseous fluorine detection. • The dark gray color of hydrogenated Pd-TiO₂ changed (back) to light gray upon exposure to XeF₂ gas. • An increase of 100× is observed in current level upon XeF₂ gas treatment simultaneously. Fluorine-containing gases (e.g., CF₄, SF₆, and XeF₂) are utilized in various industrial processes. However, these gases are toxic and detection of their leakage is crucial for safety reasons. In this study, the detection mechanism of a fluorine-containing gas is provided by hydrogenated palladium loaded on titanium dioxide (Pd-TiO₂) upon XeF₂ gas exposure. The color of the Pd-TiO₂ nanocomposite changed from light gray to dark gray after hydrogen annealing. When the Pd-TiO₂ was exposed to XeF₂ gas, the initial light gray color was restored. The reflectance of Pd-TiO₂ increased from 15% to 30% after XeF₂ treatment. Incorporation of H and F resulted in an increase in the intensity of Ti³⁺ signal in EPR and a change in the sub-gap electronic state, identified using UV–vis spectroscopy, with H₂ and XeF₂ gas treatment of bulk TiO₂. A physiochemical model and electronic band structure is suggested by based on these results as well as XPS results for the reaction and gasochromic mechanism. The results also indicate electrical response of Pd-TiO₂ to F sensing at 100 of conductance ratio of sensing to standby condition, suggesting the possibility of bimodal gaseous F detection.