Ti dispersion on SBA-15 porous host to enhance photocatalytic hydrogen production

Ti-SBA-15-based photocatalysts were synthesized using two titanium sources (Ti tetra-isopropoxide and TiO2P25) and two Si/Ti molar ratios and were compared to the bulk TiO2 (P25) in a water splitting reaction to produce hydrogen. The goal of the work is to deposit the catalysts into a hexagonal mesoporous support (SBA-15) in order to enhance TiO2 efficiency. Two Si/Ti molar ratios (20 and 40) were used to verify the influence of the Ti content inside of the porous host on hydrogen production. The photocatalysts were characterized by powder X-ray diffraction (XRD), nitrogen adsorption-desorption measurements and transmission electron microscopy (TEM) imaging. Information on the nature of the Ti species present in Ti-SBA-15-based samples was obtained using diffuse UV-visible spectroscopy and Fourier transform infrared (FTIR) spectroscopy. A positive effect in photoactivity was found in Ti-SBA-15-based samples compared to bulk TiO2. TiO2 nanoclusters and Ti-coordinated species (penta-, hexa- or octahedral) that were highly dispersed in the SBA-15 silica were found in samples that were prepared using Ti tetra-isopropoxide. TiO2P25 introduced inside the SBA-15 favored Ti dispersion into the SBA-15 mesostructure, and octahedrally coordinated Ti migration into the SBA-15 was found in these samples. In higher Si/Ti molar ratios, the Ti coordinated isolated species are more concentrated and improve the photoactivity in the water splitting reaction when using Ti tetra-isopropoxide compared to bulk TiO2P25 as a Ti source.