Photocatalysis of dye-sensitized TiO2 nanoparticles with thin overcoat of Al2O3: Enhanced activity for H2 production and dechlorination of CCl4

Abstract

Dye-sensitized TiO2 nanoparticles that were loaded simultaneously with Pt and Al2O3 overlayer (Al2(VTi(V 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 Al2(V 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 Al2O 3 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 on TiO2/Pt to 0.9 and 7.5 ΜM min on Al2O 3/ TiO2/Pt, respectively. The visible light activity of the sensitized photocatalytic reactions highly depended on the thickness of the alumina layer and was optimized at a low level of Al loading (Al/Ti atom ratio ∼ 0.01), above which the activity was markedly reduced with thickening of the layer. It is suggested that the alumina layer retards the charge recombination