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Organized Nanostructured TiO2 Materials: Synthesis, Characterization, Applications
Zukalová, Markéta ; Rathouský, Jiří (advisor) ; Mička, Zdeněk (referee) ; Šubrt, Jan (referee)
CONCLUSIONS It has been known for a long time that material properties change on the nanoscale and are different from those of single crystals or conventional microstructured, monolithic or composite materials32. The presented thesis aimed at demonstration of the diversity in these properties for various morphologies of TiO2. Despite the fact that the chemical composition is identical, the structure of different morphologies matters and it is respon-sible for their specialty. The successfully mastered syntheses of desirable particle size materials open the pathway towards applications taking advantage of size dependent properties. DSC employing 2μm mesoporous TiO2 film as a photoanode exhibited the solar conversion efficiency as high as 4.63% due to the large surface area (roughness fac-tor). Optimized pore size together with the framework consisting of anatase nanocrystals are responsible for the high dye adsorption capacity improving the performance. Incorporating an additional inverse opal layer in DSC represents an example of its further possible upgrade. This optimized set up can increase the short circuit photocurrent effi-ciency of this device of about 26 % (Ref.39). Owing to the diffusion coefficient of an order of 10-13 cm2/s for microcrystalline spinel and even less for nanocrystalline spinel...
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Electrochemical and spectroelectrochemical study of nanocrystalline TiO2 anatase with exposed (001) faces
Lásková, Barbora ; Zukalová, Markéta ; Bouša, Milan ; Kavan, Ladislav ; Liska, P. ; Grätzel, M.
The electrochemical and spectroelectrochemical behavior ot TiO2 anatase with a predominant (001) face was studied and compared to a reference anatase material with dominating (101) face. The electrochemical measurements indicate that Li-ion insertion/extraction is facilitated for TiO2 anatase with (001) faces as compared to (101) one. The performance of both different crystal morphologies as a photoanode material in DSC (dye sensitized solar cell) was tested too. The (001) face adsorbed smaller amount of the used dye sensitizer (C101) but provides larger open circuit voltage (Uoc) of the solar cell. The different band energetics of both particular morphologies was suggested to be the reason for the voltage enhancement of the device employing (001) anatase. To prove our hypothesis and determine their flatband potential, a spectroelectrochemical study of transparent films of nanocrystalline (001) and (101) anatase on coaducting glass was carried out. UV/Vis spectra were measured at potentials between 0 and -1.4V vs SCE and confirmed the negative shift of flatband potential for (001) anatase as compared to (101) one.
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