Tuning the metal-support interactions in titanium dioxide-supported palladium photocatalysts against toluene in air

The activity of supported noble metal (e.g., palladium (Pd)) catalysts is often governed by the combined effects of multiple factors (e.g., electronic and geometric properties of the support, surface chemistry of metal nanoparticles (NPs), and metal-support interactions). Pd/titanium dioxide (TiO₂) catalyst has been developed as a highly efficient photocatalytic degradation (PCD) system against gaseous toluene based on high-temperature pretreatment (300 and 450 °C) in a mixed stream of hydrogen (H₂) and (N₂). The interaction of Pd NPs with TiO₂ synergistically improves the PCD efficiency of toluene through the efficient adsorption and activation of toluene as well as molecular oxygen (O₂) and water (H₂O) for the facile generation of reactive oxygen species (ROS (e.g., superoxide anion (•O₂^-) and hydroxyl (•OH) radicals)). The PCD efficiency of the prepared sample against 5 ppm toluene (at 20% relative humidity (RH)) is 79.6% with the values of maximum reaction rate, quantum yield, space-time yield, and clean air delivery rate as 9.9 μmol g^-1 h^-1, 1.68E-03 molecules photon^-1, 1.68E-02 molecules photon^-1 g^-1, and 4.8 L h^-1, respectively. Based on this research, the PCD mechanism of gaseous toluene has been explored along with the dynamic behavior of O₂ and H₂O for ROS generation and their relative contribution to the PCD of toluene. As such, this research offers a perspective for designing advanced photocatalysts through surface defect engineering.