Effects of calcination temperature on the microstructures and photocatalytic activity of titanate nanotubes

Titanate nanotubes were prepared via a hydrothermal treatment of TiO2 powders (P25) in a I OM NaOH solution at 150 degrees C for 48h and then calcined at various temperatures. The as-prepared titanate nanotubes before and after calcination were characterized with XRD, TEM, HRTEM, SEM, FESEM, and nitrogen adsorption-desorption isotherms. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic oxidation of acetone in air. The effects of calcination temperature on the phase structure, crystallite size, morphology, specific surface area, pore structures and photocatalytic activity of the titanate nanotubes were investigated. The results indicated that at 400 to 600 degrees C, the calcined nanotube samples showed a higher photocatalytic activity than Degussa P25. Especially, at 400 and 500 degrees C, the photocatalytic activity of the calcined nanotubes exceeded that of P25 by a factor of about 3.0 times. This could be attributed to the fact that the former had a larger specific surface area and pore volume. With further increase in the calcination temperature from 700 to 900 degrees C, the photocatalytic activity of the calcined nanotube samples greatly decreased due to the formation of rutile phase, the sintering and growth of TiO2 crystallites and the decrease of specific surface area and pore volume. (c) 2006 Elsevier B.V. All rights reserved.