(189u) Synthesis of Doped TiO2 Metal Oxide Nanoparticles in Supercritical CO2

TiO2 nanoparticles are interesting for many applications due to their photocatalytic properties. However, TiO2 activity is reduced to the region of UV light (wavelength around 360 nm). In order to harness the abundant and safe potential of solar energy, the development of processes to enhance and shift the absorption of TiO2 to the visible region is of the great importance. One of the ways to extend the absorbance of TiO2 is transition metal doping in the lattice of TiO2 [1]. Different techniques have been investigated for the metal ion-implantation into TiO2 powder catalyst, such as ion-implantation, wet impregnation, ion beam induced chemical vapor deposition (IBICVD), and the sol?gel method.

In this work, supercritical CO2 is used as reaction medium for the synthesis of doped TiO2 nanoparticles with two different metals: Fe and Pd.

In the experimental procedure, diisopropoxititanium bis(acetylacetonate) is used as titania precursor and Iron (III) acetylacetonate and Pd(hfa)2 for the doping metal ion. Under the supercritical conditions metal oxide particles are formed as a result of the metal salt hydrolysis and followed dehydration reaction under the supercritical conditions [2]. The great advantage of this technology is that the nanoparticle doping takes place during the synthesis process. The synthesis of doped TiO2 nanoparticles in batch and continuous flow reactors are presented. The wide range reactions at temperature (200 ? 400 °C) and pressure (200 -250 bar) have been tested. Photocatalytic activities for the degradation of methyl orange under visible light irradiation are tested for the doped TiO2 and they are compared to the non-doped sample.

Keywords: doped TiO2 nanoparticles, synthesis, supercritical CO2.

References

[1] Kitano M., Matsuoka M., Ueshima M., Anpo M., ?Recent developments in titanium oxide-based photocatalysts? Review, Applied catalysis A, 2007, 325, 1-14.

[2] Alonso E., Montequi I., Lucas S., Cocero M.J., ?Synthesis of titanium oxide particles in supercritical CO2: Effect of operational variables in the characteristics of the final product?, Journal of Supercritical fluids, 2007, 39 (4), 453-461.