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 TiO2 photocatalysis and dye-sensitized TiO2 applications. Mesoporous TiO2 (meso-TiO2) consisting of compactly packed nanoparticles can be a promising candidate for such purposes. In the present study, meso-TiO2 exhibiting an enhanced photocatalytic activity for H2 evolution was synthesized by a simple and facile, template-free nonhydrothermal method. The photocatalytic activity for H2 evolution of meso-TiO2 was the highest compared to nonporous colloidal-TiO2 and commercial Degussa P25 (P25) and Hombikat UV-100 (HBK) samples. The highest activity of meso-TiO2 was further supported by photocurrent generation and photoluminescence. Under visible light irradiation, the dye-sensitized TiO2 system also exhibited a higher activity for H2 production with meso-TiO2 compared with colloidal-TiO2. The activity of meso-TiO2 exhibited a unique dependence on Pt cocatalyst loading. Under both UV and visible light irradiation, the highest activity for H2 production was obtained around 0.1 wt % Pt and further increase reduced the activity, whereas other nonporous TiO2 samples exhibited a typical saturation behavior with increasing Pt load. The enhanced photocatalytic activity of meso-TiO2 is ascribed to the compact and dense packing of TiO2 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-TiO2 photocatalyst.