Photodegradation by a Heterogeneous Mixture of Micro-Sized Anatase and Truncated Rhomboid Anatase Hollow Spheres

Highly uniform hollow spheres were assembled from truncated rhomboid anatase TiO2 nanoparticles (HS), which were synthesized from the hydrothermal treatment of a NaF solution by using amorphous TiO2 spheres as a precursor and template. The submicron hollow spheres with highly photocatalytic active surfaces exhibited excellent photocatalytic behavior. In this investigation, the factors that enhanced the photocatalytic performance were examined in terms of light harvesting, photoefficiency, and reaction activity. The photocatalytic performance was increased by a factor of approximately 1.5 for the scattering structure of submicron hollow spheres than that of nanofragments of submicron hollow sphere powder. The rate constant of anatase TiO2 with specific photoactive surfaces at {001} and {101} was approximately six times higher than that of randomly exposed TiO2 particles. Furthermore, a heterogeneous mixture of the submicron hollow spheres and micro-sized anatase TiO2 (HS@micro-sized TiO2) prohibited electron-hole recombination in the catalyst during the degradation reaction. The rate constant for the heterojunction system was 3.4times greater than that of the individual constituents. The rate constant for HS@micro-sized TiO2 (k=0.175min-1) was 1.8times larger than that of commercial P25 (k=0.099min-1). HS@micro-sized TiO2 is a promising photocatalytic material.