Enhanced Photocatalytic Production of H2 on Mesoporous TiO2 Prepared by Template-Free Method: Role of Interparticle Charge Transfer

Abstract

Efficient charge separation and transport are important factors in achieving high efficiency in TiO 2 photocatalysis and dye-sensitized TiO 2 applications. Mesoporous TiO 2 (meso-TiO 2 ) consisting of compactly packed nanoparticles can be a promising candidate for such purposes. In the present study, meso-TiO 2 exhibiting an enhanced photocatalytic activity for H 2 evolution was synthesized by a simple and facile, template-free nonhydrothermal method. The photocatalytic activity for H 2 evolution of meso-TiO 2 was the highest compared to nonporous colloidal-TiO 2 and commercial Degussa P25 (P25) and Hombikat UV-100 (HBK) samples. The highest activity of meso-TiO 2 was further supported by photocurrent generation and photoluminescence. Under visible light irradiation, the dye-sensitized TiO 2 system also exhibited a higher activity for H 2 production with meso-TiO 2 compared with colloidal-TiO 2 . The activity of meso-TiO 2 exhibited a unique dependence on Pt cocatalyst loading. Under both UV and visible light irradiation, the highest activity for H 2 production was obtained around 0.1 wt % Pt and further increase reduced the activity, whereas other nonporous TiO 2 samples exhibited a typical saturation behavior with increasing Pt load. The enhanced photocatalytic activity of meso-TiO 2 is ascribed to the compact and dense packing of TiO 2 nanoparticles forming a uniform agglomerate, which enables efficient charge separation through interparticle charge transfer. Finally, the present simple synthesis method we developed is advantageous over other methods because it eliminates the use of templates and a hydrothermal process, which is highly favored for the scale-up production of the meso-TiO 2 photocatalyst.