Photodegradation of rhodamine B in water assisted by titania nanorod thin films subjected to various thermal treatments

Well-crystallized titania nanorod thin films with high specific surface areas were synthesized through in situ oxidation of metallic titanium substrates with hydrogen peroxide solutions at a low temperature of 80 degrees C. The effects of thermal treatments on the ability of the thin films to assist photodegradation of rhodamine B in water were studied in detail. It is found that, due to a unique nanofeature, the titania nanorod film retained its small grain size and high specific surface area during the subsequent thermal treatment for up to 450 degrees C, which further improved the crystallinity of titania. In addition, upon heating to 450 degrees C, the nanorods still possessed a high surface fractal dimension, which is an indication of high surface roughness and surface area. As a result, the photocatalytic activity of the titania nanorod film is found to increase with an increasing heating temperature for up to 450 degrees C. The subsequent thermal treatment at temperatures beyond 450 degrees C decreased the photocatalytic activity, because of the significantly reduced specific surface area. The current investigation provided a simple and easily scaled-up approach to produce photocatalysts for efficient removal of dye effluents in wastewater.