Characterization of Pt-TiO2 film used in three formaldehyde photocatalytic degradation systems: UV254 nm, O3+UV254 nm and UV254+185 nm via X-ray photoelectron spectroscopy

Photocatalytic degradation of gaseous formaldehyde for 35 h was performed using Pt-TiO2 film in the following irradiation systems: UV254 nm, O-3+UV254 nm, and UV254+185 nm. Concurrent improvements in formaldehyde degradation and O-3 removal were achieved by modifying TiO2 with Pt nanoparticies, resulting in a 3.1-3.4-fold O-3 elimination increase. X-ray photoelectron spectroscopy (XPS) of the Pt-TiO2 film was carried out to assess the electronic states of the Pt nanoparticles and accumulated organic species. The deconvoluted C 1s and O 1s XPS spectra revealed that the content of carbonyl and carboxyl groups on Pt-TiO2 and degree of catalyst deactivation in the systems studied decreased in the following order: UV254 nm > O-3+UV254 nm > UV254+185 nm. Metallic Pt-0 was oxidized to a mixture of PtOads and Pt4+ species under O-3+UV254 nm. and UV254.185 nm irradiation owing to the presence of O-3 and hydroxyl radicals, but remained stable under UV234 nm irradiation. Pt species at higher oxidation states can act as electron trapping centers, and improve the photocatalytic activity of Pt-TiO2 and provide reactive sites for O-3 decomposition under UV irradiation, resulting in a faster O-3 removal rate than that displayed by TiO2. The XPS studies provided valuable information to elucidate the beneficial role of Pt species and the reduction of catalyst deactivation under UV254+185 nm irradiation. (C) 2014, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.