Synergism between two polymorphs of TiO2 (Anatase and Rutile) was studied for the photo catalytic water splitting reaction [1]. TiO2 anatase with particle size of 10-15nm was synthesized by sol gel method and compared to commercial grades TiO2 anatase with the particle size of 15-20nm (nano) and 100nm (micro). TiO2 anatase was heated at elevated temperature to obtain partial or full transformation of the anatase phase to the rutile phase. The transformation from anatase to rutile is initial particle size dependent as higher temperature is needed for 100nm particle size anatase for phase transformation to rutile [2]. On this differently prepared mixed phases Pt was deposited and each series was tested for the photocatalytic production of hydrogen from water in presence of sacrificial agent (under identical conditions). Catalysts were characterized by UV-Vis, XRD and XPS. Based on rates per unit mass no synergism for hydrogen production was seen in most cases; this is in part due to the decrease in the BET surface area during the phase transformation. However, strong synergism was observed for hydrogen production rates per unit area when the initial starting semiconductor was anatase 15-20nm (while no synergism seen in the case of the larger crystallite size15-20nm. Maximum rate observed was in the 10-30% rutile range. Possible reasons for these differences are discussed. Attempts to correlate the reaction rate to other semiconductor properties including degree of crystallinity, charge carriers dynamics and photocurrent are underway. [1] K. Connelly, A. K. Wahab and H. Idriss, Materials for Renewable and Sustainable energy 1 (2012)1-12 [2] H. Zhang and J. F. Banfield, Journal of Physical Chemistry B 104 (2000) 3481-3487.

Synergism between anatase and rutile: Effect of Initial particle size of TiO2 for photocatalytic water splitting

249th National Meeting (2015)

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