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Zusammenfassung:
Amorphous titania-based photocatalysts are synthesized using a facile, UV-light mediated method and evaluated as photocatalysts for hydrogen evolution from water/methanol mixtures. The photocatalysts are prepared through the direct injection of a titanium alkoxide precursor into a water/methanol mixture, with subsequent hydrolysis, condensation, and polycondensation to form TiOx(OH)y species under UV-irradiation. The resulting amorphous titania materials exhibit an overall higher hydrogen evolution rate compared to a crystalline TiO2 reference (P25) on a molar basis of photocatalyst due to the highly porous structure and high surface area (~500 m2/g). The employed titanium alkoxide precursor did not play a major role in affecting the hydrogen evolution rate or the catalyst surface and morphology. A blue coloration, which is associated with the formation of Ti3+ species, was observed in the amorphous titania but not in P25 upon light irradiation and is enabled by the porous and disordered structure of the amorphous photocatalyst. The Ti3+ species are also used to reduce protons to H2 in the absence of light irradiation or reduce Pt2+ to form Pt nanoparticles. These Pt nanoparticles are smaller and better dispersed on the photocatalyst compared to particles prepared using conventional photodeposition, leading to higher H2 evolution rates. The results show that the direct injection method is a facile approach for the preparation of high surface area titania photocatalysts containing Ti3+ species with good photocatalytic activity for production of H2.
