Temperature assisted acid catalyzed peptization of TiO2; facile sol-gel approach for thermally stable anatase phase

Abstract

High temperature stable, phase pure anatase has been successfully synthesized by temperature assisted acid catalyzed peptization of hydrous titania through an aqueous sol-gel method. This facile method does not contain any metal or non metal dopants and is very effective in extending the anatase to rutile phase transformation by 200 degrees C. The temperature maintained during the peptization process has a significant effect on the particle size and morphology of titanium dioxide. The sol synthesized by peptization at 60 degrees C has the lowest particle size of 65.2 nm and after calcination at 800 degrees C, has a crystallite size of similar to 53 nm. The relatively higher particle size of other samples is attributed to the aggregation of particles at respective peptization temperatures. An optimum temperature of 60 degrees C is effective in minimising the aggregation behaviour of titania sol which further increases the photocatalytic activity. Titanium dioxide peptized at 60 degrees C has higher photocatalytic activity (similar to 86%) than the one peptized at 30 degrees C (similar to 74%) under UV-A exposure for 100 minutes with apparent rate constants 0.02 and 0.01 min(-1) respectively. An increased anatase to rutile transformation temperature of 800 degrees C will be very useful in increasing the annealing especially in ceramic substrates. Thus highly photoactive nanocrystalline titania containing thermally stable anatase that can be used for high temperature photocatalytic applications has been synthesized.