TY - JOUR A1 - Helbig, Uta A1 - Herbst, Kai A1 - Roudenko, Jewgeni A1 - Helbig, Jens A1 - Barton, Bastian A1 - Kolb, Ute T1 - Carbon-doped titania as a precursor for titanate nanotubes JF - Journal of Materials Research N2 - Carbon-doped titania was fabricated via carbothermal treatment in nitrogen–acetylene gas flow and further used as a precursor for multiwalled titanate nanotube (TNT) synthesis via alkaline hydrothermal route. Investigation of the reaction products after hydrothermal treatment of carbon-doped titania using Transmission electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller method shows the successful formation of TNTs. The presence of carbon was proved although the type of incorporation could not be certified. All samples show approximately the same carbon content before and after hydrothermal treatment. An increasing pretreatment temperature of titania precursor powders yields more secondary products in the nanotube samples, indicating lower reactivity of the titanium oxycarbide phase during hydrothermal treatment. In this study, TNTs with 6 wt% carbon and with the highest specific surface area of 340 m2/g were formed via hydrothermal treatment of carbon-doped titania precursor powder exposed to 700 °C during carbothermal pretreatment. Y1 - 2018 U6 - https://doi.org/10.1557/jmr.2018.49 SN - 0884-2914 VL - 33 IS - 9 SP - 1288 EP - 1300 PB - Springer Science and Business Media LLC ER - TY - JOUR A1 - Eitel, Dominik A1 - Graml, Johanna A1 - Hoppe, Julia A1 - Kaliwoda, Melanie A1 - Hornfeck, Markus A1 - Helbig, Uta T1 - Synthesis and Structure of Carbon-doped TiO2 by Carbothermal Treatment JF - Nano Select N2 - Carbon modified titanium dioxide (TiO2) is a promising candidate for catalytic applications or fuel cells, where the modified oxide could replace currently used catalyst support materials. Carbothermally treated TiO2 was successfully prepared by annealing under acetylene/nitrogen gas flow in a rotary tube furnace. The carbon content in the TiO2 samples ranged from 5 to 14.5 wt.-% as determined by thermogravimetric measurements. The powders showed suppression of the phase transition from anatase to rutile up to a treatment temperature of 825°C. Above 600°C rutile is the thermodynamically stable phase, therefore the suppression must be attributed to either carbon in the lattice or the reducing atmosphere in the furnace. Raman spectra revealed the characteristic G and D bands, indicating the formation of carbonaceous species in the samples. In addition, a shift of the anatase Eg(1) band was observed indicating a lattice disorder pointing toward carbon incorporation into the lattice. Diffuse reflectance spectra show sub band gap absorption together with a shift of the absorption edge. Depending on the extraction method of band gaps from spectra, the band gap values show a decrease or increase with increasing carbon content. Details of the evaluation and interpretation of the spectra are discussed. KW - Nanotechnologie KW - Brennstoffzelle Y1 - 2023 U6 - https://doi.org/10.1002/nano.202300022 SN - 2688-4011 VL - 4 IS - 7 SP - 454 EP - 461 PB - Wiley ER - TY - JOUR A1 - Seiß, Volker A1 - Helbig, Uta A1 - Lösel, Ralf A1 - Eichelbaum, Maik T1 - Investigating and correlating photoelectrochemical, photocatalytic, and antimicrobial properties of TiO2 nanolayers JF - Scientific Reports N2 - Semiconducting transition metal oxides such as TiO 2 are promising photo(electro)catalysts for solar water splitting and photoreduction of CO 2 as well as for antibacterial, self-, water and air-cleaning coatings and admixtures in paints, building materials, on window glass or medical devices. In photoelectrocatalytic applications TiO 2 is usually used as photoanode only catalyzing the oxidation reaction. In coatings and admixtures TiO 2 works as heterogeneous catalyst and has to catalyze a complete redox cycle. While photoelectrochemical charge transport parameters are usually quite well accessible by electrochemical measurements, the quantitative description of photocatalytic properties is more challenging. Here, we present a systematic structural, photoelectrocatalytic, photocatalytic and antimicrobial study to understand if and how photoelectrochemical parameters can be used to predict the photocatalytic activity of TiO 2. For this purpose TiO 2 thin films on flourine-doped tin oxide substrates were prepared and annealed at temperatures between 200 and 600 ◦C. The film morphologies and thicknesses were studied by GIXRD, FESEM, and EDX. Photoelectrochemical properties were measured by linear sweep voltammetry, photoelectrochemical impedance spectroscopy, chopped light chronoamperometry, and intensity modulated photocurrent/photovoltage spectroscopy. For comparison, photocatalytic rate constants were determined by methylene blue degradation and Escherichea coli inactivation and correlated with the deducedphotoelectrocatalytic parameters. We found that the respective photoactivities of amorphous and crystalline TiO 2 nanolayers can be best correlated, if the extracted photoelectrochemical parameters such as charge transfer and recombination rates, charge transfer efficiencies and resistances are measured close to the open circuit potential (OCP). Hence, the interfacial charge transport parameters at the OCP can be indeed used as descriptors for predicting and understanding the photocatalytic activity of TiO 2 coatings. KW - Multidisciplinary Y1 - 2021 U6 - https://doi.org/10.1038/s41598-021-01165-x SN - 2045-2322 VL - 11 SP - 1 EP - 16 PB - Springer Science and Business Media LLC ER -