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. Graphical Abstract: [Figure not available: see fulltext.]