HIERARCHICAL HETEROSTRUCTURE OF RUTILE TiO2 NANOFLOWER ARRAY ON ANATASE TiO2 SHEET WITH ENHANCED PHOTOCATALYTIC PERFORMANCE

Hierarchical heterostructure of rutile TiO2 nanoflower array on anatase TiO2 sheet was fabricated by a two-step method. Anatase TiO2 sheet was synthesized by a modified dip coating method, followed by the formation of rutile TiO2 nanoflower array via a wet chemical route. Studies by X-ray diffraction and scanning electron microscopy indicated the formation of hierarchical heterostructure. Tests on degradation of methylene blue under UV light illumination showed that the hierarchical TiO2 film exhibited superior photocatalytic performance to those with monophased anatase and rutile TiO2 films and commercial P25 film. It was attributed to efficient separation of photogenerated charge carriers and prevention of the unfavorable multiple electron transfer on biphase interface. Investigation on the influence of addition of scavengers on photocatalysis suggested that hydroxy radicals and superoxide anion radicals dominated the photocatalytic degradation of MB. The hierarchical TiO2 film exhibited excellent photocatalytic stability in cycling tests.