Photocatalytic properties of nanostructured TiO₂ containing materials for splitting of H₂O

Photocatalysis involves phenomena occurring at high time resolutions under unique conditions. Studies probing these time scales under relevant in situ conditions will lead to improved photocatalysts. Thus, catalysts containing 1-60 wt% TiO₂/SiO₂ were dehydrated under flowing 10% O₂ at 400 °C. Using a pulsed laser for excitation and a gated detector with picosecond time resolution, the lifetime of excited states of the samples was determined in situ at room temperature. H₂ production was monitored by gas chromatography for the water splitting reaction in a UV-irradiated reactor. The excitation lifetime measurements indicate that lower wt% samples have longer excited lifetimes, which correlates with increased specific H₂ production rates. The water splitting reaction's intermediates and product formation were monitored using attenuated total reflectance (ATR) Fourier transform infrared (FT-IR) spectroscopy during transient UV irradiation. Hydrogen titanate nanotubes were also prepared using a hydrothermal method. It was shown with in situ Raman spectroscopic characterization that post synthesis thermal treatment transforms the titanate nanotubes to TiO₂ (anatase) nanotubes. The photocatalytic water splitting activity of the TiO₂ nanotubes were also determined. This presentation will develop the relationship between the titania structure-photoactivity properties for the different TiO₂ nanodomains (supported TiO₂/SiO₂ and unsupported TiO₂ nanotubes).