Photothermal synergistic effect of M/TiO₂ nanofiber catalysts prepared by electrospinning in removing VOCs

In this work, a series of M/TiO₂ (M= Cu, Mn, Co, Ni) nanofiber catalysts were prepared by electrospinning technology, and their photothermal synergism on toluene oxidation was investigated. The sequence in catalytic activity for the oxidation of toluene was Cu/TiO₂ > Mn/TiO₂ > TiO₂ > Co/TiO₂ > Ni/TiO₂. The excellent catalytic performance of Cu/TiO₂ came from its good low-temperature reducibility and lattice oxygen mobility. The activation ability of photo-generated carriers for O2 and lattice oxygen is the reason why Cu/TiO₂ have the best promotional effect of light irradiation. In situ DRIFTS revealed the reaction pathway of photothermal catalytic oxidation of toluene on Cu/TiO₂: Toluene and O2 first reacted with holes and electrons to generate benzyl radicals and O2 -. These benzyl radicals and superoxide radicals then couple with protons to form hydro-peroxide intermediates. The hydro-peroxide intermediates undergone dehydration to form benzaldehyde, which was further oxidized by O- ions to yield benzoic acid. Finally, benzoic acid was completely oxidized to CO2 and H2O. In this process, the adsorbed oxygen promoted the generation of benzaldehyde, while lattice oxygen mainly promoted the further decomposition of benzaldehyde.