Abstract
The size of TiO2 can significantly affect both its photocatalytic and photo-electrochemical properties, thus altering the photooxidation of organic pollutants in air or water. In this work, we give an account of the photo-electrochemical and photocatalytic features of some nanosized TiO2 commercial powders towards a model reaction, the photooxidation of acetone. Cyclic voltammograms (CV) of TiO2 particulate electrodes under UV illumination experiments were carried out in either saturated O2 or N2 solutions for a direct correlation with the photocatalytic process. In addition, the effect of different reaction conditions on the photocatalytic efficiency under UV light in both aqueous and gaseous phases was also investigated. CV curves with the addition of acetone under UV light showed a negative shift of the photocurrent onset, confirming the efficient transfer of photoproduced reactive oxygen species (ROSs), e.g., hydroxyl radicals or holes to acetone molecules. The photocatalytic experiments showed that the two nano-sized samples exhibit the best photocatalytic performance. The different photoactivity of the larger-sized samples is probably attributed to their morphological differences, affecting both the amount and distribution of free ROSs involved in the photooxidation reaction. Finally, a direct correlation between the photocatalytic measurements in gas phase and the photo-electrochemical measurements in aqueous phase is given, thus evincing the important role of the substrate-surface interaction with similar acetone concentrations.
Highlights
Semiconductor photocatalysts have been intensively investigated because of their applicability in the treatment of pollutants in both air and water phases
The XRD spectra reveal the presence of the pure anatase phase fo quoted samples but P25, which contains a 75:25 ratio of anatase-to-rutile phase [ morphological aspects of all samples were examined by high resolution electron transmission microscopy (HR-TEM) (Figure 1)
Nan powders (P25 and PC105) exhibit the typical average particle size of 20–30 nm. more, the nanosized materials are homogeneous with well-packed cry3sotaf 1l6line par parallel with this, a distinctive morphology could be noticed in the larger-sized (1077 and AH-R)
Summary
Semiconductor photocatalysts have been intensively investigated because of their applicability in the treatment of pollutants in both air and water phases. The extremely small size of nanopowder crystallites confers them a high specific surface area, which may result in a prospectively greater reactivity compared to larger sized powders [6]. Widespread attention has been directed to the development of TiO2 powders with very small crystallite size in an effort to enhance the photocatalytic activity and process efficiency. In order to substitute nano-sized particles in industrial and environmental remediation processes, the current research is investigating the photocatalytic efficiency of TiO2 materials possessing larger crystallite size. Some reports have successfully demonstrated the interesting catalytic performance of commercial sub-micro-sized TiO2 powders sold as pigmentary materials [14,15]. The efficiency has been tested towards the photodegradation of (i) both NOx and volatile organic compounds (VOCs) in gas phase and (ii) some organic dyes dissolved in water [16,17]
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