Paper SE-TuA8
The Role of Carbon in Anatase as Visible Light Photocatalyst

Tuesday, October 21, 2008, 4:00 pm, Room 204

Titania is known as the favorable material as photocatalyst. However, the wide bandgap of titania limits its efficient utilization of solar light with most photon energies below the bandgap of titania. In this paper, we report that titania powders synthesized by low-pressure flat-flame metalorganic chemical vapor deposition shows high photocatalytic efficiency under visible light illumination. 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 by carrier gas flow rate such that 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 synthesized under slightly oxygen deficient environment possesses best photocatalytic efficiency under illumination of visible light. The reaction rate constant is even higher than that of ST-01 titania powder, which is commercially available for photocatalytic applications. The visible light absorption is resort to the presence of carbon since no other chemical bonds not associated with carbon are chromophores. It also suggest that carbon species are associated with catalytic site on anatase surface so that carriers generated by photon absorption by the carbon species can transfer quickly onto catalytic sites and perform the subsequent catalytic reactions. 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.