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Vytváření tenkých vrstev pro aplikace pokročilých oxidačních procesů s využitím kovových dopantů
KRAJČOVIČ, Jan
Cílem této diplomové práce bylo nanesení tenkých vrstev TiO2 na různé typy a velikosti substrátů, přičemž některé vrstvy vytvořit s využitím dopantů železa nebo stříbra. V rámci práce byla nanesena řada vrstev TiO2 metodou magnetronového naprašování na aparatuře Dreva ARC 400 Hard Material Coating Plant. Hlavním cílem nanášení těchto vrstev bylo, pokusit se nanést tenké vrstvy TiO2 na substráty o větší ploše, než je při běžných laboratorních procesech běžné. Za tímto účelem byly vrstvy nanášeny na čtvercové skleněné destičky o straně 10 cm. Pro porovnání a zkoumání dalších vlastností nanesených vrstev byly jako substráty použity také mikroskopická sklíčka a úlomky z křemíkových destiček. Na těchto substrátech byla poté testována fotokatalytická aktivita a morfologie nanesených vrstev. Teoretická část této práce je zaměřena na používané metody nanášení tenkých vrstev TiO2 a jejich vlastnosti. V experimentální části je pak popsána použitá aparatura a parametry jednotlivých depozičních procesů. Dále je zde shrnutí vlastností nanesených vrstev a výsledky jednotlivých experimentů.
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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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Modification of TiO2 electronic properties by means of chemical treatment (doping)
Zukalová, Markéta ; Lásková, Barbora ; Procházka, Jan ; Bastl, Zdeněk ; Havlíček, D. ; Kavan, Ladislav
The product of the reaction of nanofibrous anatase with ammonia in gas phase is nanofibrous cubic titanium oxynitride, c-TiO2N3. In contrary to the preparation of cubic titaniurn oxynitride from microcrystalline TiO2, requiring temperatures above 800°C, the conversion of nanofibrous TiO2 to TiO2N3 is completed at about 500°C due to its enhanced chemical reactivity. This conversion is fully reversible; the product of the back reaction is again nanofibrous Ti02. By the thermal treatment of nanofibrous anatase in H2 flow at 800°C for 2 hours the mixture of black disordered anatase, rutile and titanium suboxides was prepared. Evidently, particular phases can be synthesized simply by tuning the temperature of the treatment, which is a subject of the further research.
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Photoelectrochemical Oxidation of Carboxylic Acids on the Sol-Gel Thin TiO2 Layer Electrode
Morozová, Magdalena ; Klusoň, Petr ; Krýsa, Josef ; Šolcová, Olga
Heterogeneous photocatalysis is based on the reaction between the light excitated semiconductor and oxidizable compound adsorbed on the catalytic surface. This work reports the photoelectrocatalytic oxidation characteristics of carboxylic acids on the TiO2 sol-gel thin-film electrode by using electrochemical techniques. The influence of the thickness of the films on photoactivity and the various concentrations of oxalic, formic and acetic acid in the supporting electrolyte were investigated. The effect of the used mono- and dicarboxylic acids on the electrode behaviour for possible application as sensors has been also studied. The surface characteristics of TiO2 films were determined by XRD, SEM and AFM analyses and the photoexcitation properties of nanoparticulate layer electrode were determined by cyclic and linear voltammetry, amperometry and open circuit potential (OCP).
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