Promoting effects of H2 on photooxidation of volatile organic pollutants over Pt/TiO2

Superior photocatalytic activity and durability of Pt/TiO2 for decomposing volatile organic pollutants (typically aromatic compounds) have been obtained by adding trace H-2 into an O-2-rich photooxidation system. The order of photodegradation efficiencies for volatile organic compounds is cyclohexane < acetone < benzene < toluene < ethylbenzene. Exceptional stability of Pt/TiO2 for benzene photodegradation is still maintained after 22 h of testing, by the repeated use of the catalyst four times. The promoting effects of H-2 in the photocatalysis were studied by infrared spectroscopy (IR), spin-trapping electron paramagnetic resonance (EPR) and surface photovoltage spectroscopy (SPS). Results demonstrated that the introduced H-2 has several beneficial effects on heterogeneous photocatalysis, namely, a comparatively clean surface of Pt/TiO2 with no persistent aromatic intermediates, an increased number of surface hydroxyl radicals in the photocatalytic process, and an enhanced separation efficiency of photogenerated electron-hole pairs. A mechanism is proposed to elucidate the promoting effect of H-2 on the photooxidation of volatile organic pollutants over Pt/TiO2.