Photocatalytic hydrogen production from aqueous methanol solution using Pt nanocatalysts supported on mesoporous TiO2 hollow shells

Abstract

Mesoporous TiO2 hollow shells were synthesized by a conventional templating method which combines sol–gel coating and selective etching of the silica cores. Pt nanocatalysts were supported on these mesoporous TiO2 hollow shells varying the metal loading: 0, 1, 3, 5 and 7 % at calcination temperatures of 500 or 900 °C. The samples were characterized by transmission electron microscopy, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, and nitrogen physisorption. The mesostructures were observed by TEM and HRTEM to be smaller than 300 nm and the TiO2 shells had an average wall thickness of 40 nm. X-ray diffraction spectra revealed a pure anatase phase in samples calcined at 900 °C, whereas those calcined at 500 °C were amorphous. Under white light (UV and Visible) illumination, photocatalytic hydrogen production was measured from the samples suspended in an aqueous solution of methanol and compared to TiO2 (P25, Degussa) used as a reference. The highest hydrogen yields were achieved with the crystalline TiO2 hollow shells annealed at 900 °C containing 1 or 7 wt% Pt. The amorphous samples were observed to be inactive, at all metal loadings.