Usage of ultrafine anatase/TiO2·nH2O powder: photocatalysis and microstructure control for nanocrystalline TiO2

As a control method, a ultrafine TiO2 powder (sample A) prepared previously acted as a primary material and was annealed at different temperatures for obtaining nanocrystalline TiO2 with different microstructures. This process without supplemental heat from gel oxidation has an important effect on the nanocrystalline TiO2 microstructures. In addition, the photocatalytic efficiency of sample A was evaluated by the methylic orange (pH=6) photocatalytic degradation with this ultrafine powder and the other typical nanocrystalline TiO2 powders. It was found that only the sample A has an excellent photocatalytic efficiency. The further characterisation by thermal analysis shows that this ultrafine powder consists of anatase phase and non-crystal TiO2·nH2O. It was explained by the TiO2 photocatalysis mechanism that the OH− belonging to ultrafine anatase/TiO2·nH2O powder (sample A) can efficiently promote the purification in low pH medium.