High Performance Crystalline TiO2 Mesocrystals for Enhanced Solar Fuel

Titanium dioxide (TiO2) is one of the most abundant compounds in our planet. It is cheap, non- toxic, highly chemically and thermally stable semiconductor material. Titanium dioxide nanoparticles (TiO2-NPs) show high visible light transparency combined with high UV light absorption. However, altering the particle size and crystalline structure of TiO2-NPs influences the absorption range, adsorption of dye molecules and electron transfer rate at the surface. Unfortunately, TiO2-NPs suffer high electron/hole recombination rates. Therefore, an ordered superstructure consisting of nanoparticles on the scale of nanometers to several micrometers is proposed titanium dioxide mesocrystals (TiO2-MCs). In this work, we represent a new and facile way to fabricate TiO2-MCs with spherical structure by sol-gel method. We were able to fabricate spherical TiO2-NCs with narrow size distribution by controlling the hydrolysis conditions. The effect of air annealing on the morphology, size shrinkage, and phase transition of the nanoparticles was studied by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Also, the fabricated TiO2-MCs showed exceptional photoactivity compared to their Degussa p-25 nanoparticles counterparts upon their use in water splitting cells.