Photocatalytic degradation of gaseous toluene and ozone under UV254+185 nm irradiation using a Pd-deposited TiO2 film

• Pd–TiO2/VUV effectively degraded toluene within short retention time (5.7 s).
• The smallest Pd particles (1.9 nm) exhibited the highest TOF for toluene and ozone.
• Over 94% of the converted toluene was transformed into CO2 and CO.
• Ozone was remarkably degraded by Pd–TiO2 with conversions up to 90%.

This study investigated the effects of palladium nanoparticles (Pd NPs) that were deposited onto a TiO2 film on the simultaneous removal of toluene and ozone byproduct during 254 nm ultraviolet and 185 nm vacuum ultraviolet (VUV) irradiation. The uniform Pd NPs that were deposited onto the TiO2 film via an electrostatic method showed a high activity for toluene and ozone conversion. Pd NPs with the smallest mean size (1.9 ± 0.7 nm) exhibited the highest turnover frequency (TOF). However, the Pd–TiO2 film prepared with an immersion time of 10 min exhibited the highest activity for both toluene and ozone conversion because of the relatively small size and high density of the as-deposited Pd NPs. Compared with the direct VUV photolysis and the TiO2/VUV photocatalytic processes, the Pd–TiO2/VUV process exhibited a better performance in degrading toluene over a range of concentrations with a short retention time (5.7 s), and 90% of the ozone generated by 185 nm VUV was simultaneously decomposed. In addition, approximately 94.1% of the converted toluene was mineralized into CO2 and CO, and only a small amount of degradation intermediates, such as benzaldehyde and formic acid, were detected in the Pd–TiO2/VUV process with a total yield less than 2%.

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