Photocatalysis of Dye-Sensitized TiO 2 Nanoparticles with Thin Overcoat of Al 2 O 3 : Enhanced Activity for H 2 Production and Dechlorination of CCl 4

Dye-sensitized TiO2 nanoparticles that were loaded simultaneously with Pt and Al2O3 overlayer (Al2O3/TiO2/Pt) were synthesized and investigated for photocatalytic activity under visible light. Introducing a thin Al2O3 overlayer (∼1 nm thick) on dye-sensitized TiO2 markedly enhanced the visible light activities for the production of hydrogen (in the presence of EDTA as an electron donor) and the dechlorination of CCl4. The Al2O3/TiO2/Pt powder was characterized by HRTEM, EDX, and XPS. In agreement with the photocatalytic activity data, the photocurrent collected via electron shuttles on a Pt electrode immersed in an aqueous photocatalyst suspension under visible light was also enhanced in the presence of an Al2O3 overlayer, which indicates an enhanced interfacial electron transfer despite the presence of an insulating surface layer. The initial H2 and chloride generation rate increased from 0.4 and 5 μM min−1 on TiO2/Pt to 0.9 and 7.5 μM min−1 on Al2O3/TiO2/Pt, respectively. The visible light activity of t...