Preparation and characterization of titania nanoparticles by microwave-hydrothermal method for dye-sensitized solar cells

M. DOS SANTOS; C. RICCARDI; R. PARRA; S. ANTONIO; P. BUENO

Natal

Congreso; International Conference Nanoscale Materials and Devices for Energy Conversion, Storage and Biosensors; 2011

Titanium dioxide (TiO2) has been the subject of a great deal of research during the last decades because of its outstanding physicochemical properties and the increasing demand for devices with enhanced properties with strong emphasis on environmental applications. Current interest is focused on the use of nanocrystalline TiO2 for the development of dye-sensitized solar cells1, photocatalysts for the degradation of water and air pollutants2, self-cleaning and energy efficient windows3, gas sensors4 and photoluminescent materials5. The properties of TiO2 are significantly dependent on the crystalline phase, i.e., anatase, rutile, or brookite6. Phase and morphology are critical parameters in determining the suitability of the material for a particular application. Because of its high photoactivity, anatase is the most favorable phase for solar energy conversion and photocatalysis7. Numerous efforts have been made toward the synthesis of high surface area anatase from different precursors (Ti(OnBu)4, Ti(OiPr)4,TiCl4, TiCl3, Ti(SO4)2) and by different synthesis routes such as hydrothermal, thermohydrolysis, and sol–gel processes8. In the present paper, we report on the phase formation and on the structural and morphological features of pure anatase. The TiO2 nanoparticles were obtained by sol–gel method9 and submitted to microwave-hydrothermal treatment at 40 Celsius degree for 5 min. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy/STEM mode (FEG/STEM) and RAMAN spectroscopy. The refined unit-cell parameters achieved by the Rietveld method of the pattern resultant from the powder obtained at 40 °C for 5 min (Figure 1) allowed us to confirm the sole presence of anatase (space group I41/amd). Final values of phase data were shown in Figure 1. The morphology of the obtained powder was characterized by means of TEM. It is shown that synthesized TiO2 powders have a particle size below 10 nm, a narrow distribution and exhibit weak agglomeration. The RAMAN spectrum showed well-defined bands at 640, 516, 403, 202 and 154 cm-1 which are the characteristic bands for anatase. Therefore, the microwave-hydrothermal method enabled cerium compounds to be synthesized at low temperature and shorter time.