| AVS 54th International Symposium | |
| Advanced Surface Engineering | Wednesday Sessions |
| Session SE-WeM |
| Session: | Photocatalytic Coatings |
| Presenter: | Y.J. Chen, National Dong Hwa University, Taiwan ROC |
| Authors: | Y.J. Chen, National Dong Hwa University, Taiwan ROC J.M. Wu, National Dong Hwa University, Taiwan ROC M.S. Wong, National Dong Hwa University, Taiwan ROC |
| Correspondent: | Click to Email |
Anatase is known as the favorable phase of titania as photocatalyst over rutile. However, several reports suggest that a mixed phase of anatase and rutile possesses even better photocatalytic efficiency. In this paper, we report that a mixed phase of anatase and rutile synthesized by low-pressure flat-flame metalorganic chemical vapor deposition does show such phenomenon that the mixed phase with proper proportion has higher photocatalytic efficiency over single phase anatase. Using acetylene and oxygen as fuel and oxidizer for the flame, the titanium isopropoxide was decomposed and oxidized, and the nanoparticles of titania were formed. The phase of titania powder can be manipulated from almost pure anatase through mixed phases and to pure rutile phase by varying the inert precursor-carrying gas flow rate. The higher the carrier gas flow, the higher the rutile content. From the methylene blue decomposition study we found that the powder with almost pure anatase phase possesses best photocatalytic efficiency under illumination of UV light. However, mixed phase shows best efficiency under visible light illumination. Furthermore, for powder annealed in nitrogen atmosphere at 150 Celsius for 3 hours, the sample of mixed phase further enhanced its methylene blue photodecomposition efficiency. The reaction rate constant is even higher than that of ST-01 titania powder, which is commercially available for photocatalytic applications. While proper annealing process increases the photocatalytic activity of the powder, prolonged or elevated temperature annealing leads to degradation of its power, even the mixed-phase configuration is still retained. It suggest that carbon species play important role in enhancement of mixed-phase photocatalytic activity, since the carbon species will be oxidized during annealing, leaving uncontaminated titania powder, which lose its enhanced catalytic power. Evidence will be provided to show that the carbon species does evolve with annealing, and the presence of carbon species is in coincident with the presence of visible light absorption.