Preparation of TiO2–SiO2 aperiodic mesoporous materials with controllable formation of tetrahedrally coordinated Ti4+ ions and their performance for photocatalytic hydrogen production

• Four sol–gel based methods were used to prepare titania-silica photocatalysts.
• Hydrothermal method produces high amounts of Ti4+ ions in tetrahedral coordination.
• Supercritical drying method resulted in large pore volumes and surface areas.
• Hydrogen production depends on the amount of Ti4+ ions in tetrahedral coordination.

The efficiency of photocatalytic water splitting for TiO2 dispersed on four SiO2 aperiodic porous supports is discussed in this work. The four TiO2–SiO2 composite materials were prepared via a sol–gel method and then subjected to supercritical drying, natural drying, rotatory vapor drying, or hydrothermal synthesis and the materials were subsequently calcined under identical conditions. These synthetic strategies result in differences in textural properties (specific surface area, pore diameter etc.) and in the amount of tetrahedrally coordinated Ti4+ ions. The TiO2–SiO2 materials were thoroughly characterized by powder X-ray diffraction (XRD), UV–Vis diffuse reflectance spectra (DRS), nitrogen adsorption studies, FT-IR spectroscopy, transmission electron microscopic (TEM) studies, and electron paramagnetic resonance (EPR) studies. The photocatalytic activity for hydrogen production is maximum when the amount of tetrahedrally coordinated Ti4+ ions is high. Thus, this work provides guidance towards the preparation of photoactive materials for generating hydrogen from water.