Photocatalytic activities of pure rutile particles isolated from TiO2 powder by dissolving the anatase component in HF solution

We have found that anatase TiO2 dissolves into an HF solution more easily than rutile TiO2, Using this property, we succeeded in isolating pure rutile particles from TiO2 powder consisting of rutile and anatase phases by the HF treatment. The isolation of pure rutile particles was confirmed by X-ray diffraction patterns and diffuse reflection spectra. The rutile particle showed much lower photocatalytic activity than the original powder, if compared for the oxidation of 2-propanol in aqueous solution using dissolved oxygen as the electron acceptor. On the other hand, when Fe(III) ions were used as the electron acceptor for oxidation of 2-propanol and water, the activity scarcely changed after the HF treatment. These results indicate that rutile TiO2 has poor activity for the reduction of oxygen, and the presence of a small amount of an anatase component is crucial for an efficient photocatalytic reaction on TiO2 particles using oxygen as the electron acceptor.