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Contribution of Cu and Zr to the Properties of TiO2 for Photocatalytic Water Treatment
Olena Pliekhova, Iztok Arčon, Nataša Novak Tušar, Urška Lavrenčič Štangar, 2017, published scientific conference contribution abstract

Keywords: Photocatalysis, water treatment, surface modification, durability
Published in RUNG: 23.08.2017; Views: 4463; Downloads: 0
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13.
Role of Surface Cu-O-Zr Sites in the Photocatalytic Activity of TiO2 Nanoscale Particles
Olena Pliekhova, Iztok Arčon, Nataša Novak Tušar, Urška Lavrenčič Štangar, 2016, published scientific conference contribution abstract

Keywords: Photocatalysis, Titanium dioxide, Copper, Zirconia, co-doping, EXAFS, XANES
Published in RUNG: 23.08.2017; Views: 4589; Downloads: 0
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14.
Structural analysis of sunlight efficient Cu and Zr modified TiO2 photocatalyst
Olena Pliekhova, Iztok Arčon, Urška Lavrenčič Štangar, 2017, published scientific conference contribution abstract

Keywords: TiO2, photocatalysis, EXAFS, surface modification
Published in RUNG: 23.08.2017; Views: 4149; Downloads: 0
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15.
Synthesis and characterization of metal/semiconductor nanocomposites for photocatalysis
Tina Mavrič, doctoral dissertation

Abstract: The doctoral dissertation focused on improving photocatalytic activity of nanopowdered ZnO by constructing I) Metal-Semiconductor and II) Semiconductor-Semiconductor heterostructures. Both heterostructure types have been reported to have a beneficial effect on photocatalytic efficiency. For the first part (I) Ag/ZnO nanocomposite was synthesized. Here we investigated an influence of polyvinylpyrrolidone (PVP) addition during the synthesis on the particle properties and their photoactivity. The second part (II) describes procedure development of ZnO based semiconductor-semiconductor composite that resulted in synthesis of highly efficient ZnO/CuWO4 composite. Ag/ZnO nanocomposite was synthesized from precursors in ethylene glycol (EG) in a hydrothermal reactor at 180 °C for 3h. No further thermal treatment was required after the synthesis since all samples showed good crystallinity. Silver precursor loading was 2.7 wt%, because this amount has shown the best photoactivity in preliminary sample testings. Two separate batches of Ag/ZnO nanopowders were prepared, one with addition of PVP, one without (labelled Ag/ZnO and Ag/ZnO*, respectively). All powders were in nanometer range, TEM images showed a major difference between the samples with and without PVP. While Ag nanoparticles were deposited uniformly over ZnO, Ag/ZnO* exhibited a substantial agglomeration of Ag. The photocatalytic efficiency was assessed under UV-Vis light. Ag/ZnO reached complete decolourization of 10–5 M methyl orange (MO) already in 80 min after the beginning of irradiation. The calculated degradation rate constant (k) for the Ag/ZnO was almost 2-times larger than for TiO2 P25 and 4-times larger than for ZnO. Ag/ZnO* also showed higher activity than pure ZnO*, but was inferior to Ag/ZnO (1.6-times of Ag/ZnO*). A reusability test performed on Ag/ZnO showed an excellent photoactivity of reused powders; second and third cycle exhibited higher photoactivity than the first cycle. The supreme photocatalytic activity of Ag/ZnO was also confirmed by degradation of terephthalic acid. To develop an efficient semiconductor-semiconductor heterostructure we have synthesized a combination of several materials with ZnO. We performed preliminary photocatalytic tests in order to assess the functionality of these heterostructures. The tested systems were the following: ZnO/MWCNT, ZnO/GO, ZnO/SiC, ZnO/Co3O4, ZnO/AgVO3. The synthesis of heterostructures was done via hydrothermal synthesis. The commercial or synthesized powers were dispersed together with the ZnO precursor in EG medium (180 °C/3h). The aim was to obtain higher photoactivity than that of pure ZnO. None of these systems was able to outperform pure ZnO. ZnO/CuWO4 system has, however, significantly improved ZnO photoactivity. Several synthesis routes were investigated, including the influence of different structure directing agents (PVP, CTAB, starch). The best performing system was obtained by separate hydrothermal synthesis of ZnO and CuWO4 in water with PVP. XRD analysis confirmed that to obtain the crystalline CuWO4 thermal treatment (500 °C) is needed. The heterostructure was also synthesized in ethanolic solution. ZnO particles were in a nanometer range, CuWO4 were larger and ranged from 200 to 400 nm. CuWO4 has successfully decreased the charge recombination in ZnO, which was confirmed by transient absorption spectroscopy studies. The photocatalytic activity was assessed for both MO and TPA (10–4 M) degradation. The ZnO/CuWO4 composite has completely decolourized the dye in 60 min of UV-Vis irradiation. k for ZnO/CuWO4 was ~2.5-times larger than that of ZnO. A 3-cycle reusability test with MO showed a small decrease in efficiency in the last cycle. TPA degradation has revealed lower efficiency for ZnO/CuWO4 in air but high efficiency in O2 and N2 atmosphere, where it reached 90% and 55% degradation rate, respectively.
Keywords: photocatalysis, zinc oxide, heterostructures, powders, Ag/ZnO composites, ZnO/CuWO4 composites
Published in RUNG: 31.05.2017; Views: 6144; Downloads: 362
.pdf Full text (4,11 MB)

16.
Transparent titania-zirconia thin films for self-cleaning and photocatalytic application
Nives Vodišek, Kandalam Ramanujachary, Vlasta Brezová, Urška Lavrenčič Štangar, 2016, published scientific conference contribution abstract

Abstract: Thin films were prepared by sol-gel process, where different amount of zirconia were added to titania. Photocatalytic activity of thin films was measured by two methods i) determination of degradation ration of methyl stearate with measuring the contact angle and ii) formation of hydroxyterephthalic acid was measured by spectrofluorometer. Prepared samples were characterized by UV-Vis spectrophotometer, SEM, XRD, FT-IR ATR, and BET. The result of measurements of photocatalytic activity shows that the highest activity has a sample without addition of zirconia, but mechanical stability of that sample is worse.
Keywords: photocatalysis, ZrO2/ TiO2, thin films, self-cleaning, low-temperature, sol-gel process
Published in RUNG: 14.03.2017; Views: 5046; Downloads: 202
.pdf Full text (462,52 KB)

17.
Transparent titania-zirconia-silica thin films for self-cleaning and photocatalytic applications
Nives Vodišek, Kandalam Ramanujachary, Vlasta Brezova, Urška Lavrenčič Štangar, 2017, published scientific conference contribution

Keywords: TiO2, ZrO2, thin films, photocatalysis, mechanical stability
Published in RUNG: 13.03.2017; Views: 4990; Downloads: 5
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18.
HETEROGENEOUS PHOTOCATALYTIC OXIDATION FOR THE REMOVAL OF BISPHENOL A FROM AQUEOUS SOLUTION OVER TiO2/GRAPHENE OXIDE (GO) BASED NANOCOMPOSITES
Ana Veternik, 2017, master's thesis

Abstract: Since water is an essential substance for all life on earth, it is therefore vital to prevent its pollution and to improve wastewater purification processes. There is a vast number of pollutants which can contaminate water, of which bisphenol A (known as an endocrine disruptor) is the pollutant studied herein. In this study, several TiO2/GO based nanocomposites with various GO loadings (2, 4, 10, 20 and 40%) and differently shaped nanocrystalline TiO2 phases (titanate nanotubes (TNTs) and calcined titanate nanotubes (TNTs_500)) were synthesised. All of the nanocomposites were characterised through SEM, UV-vis-DR, TGA, BET, FT-IR and CHNS analyses and were used in the heterogeneous photocatalytic degradation of bisphenol A and compared to the activity of pure TNTs and TNT_500 photocatalysts. All TiO2/GO nanocomposites exhibit much better activity than pure TNTs and TNTs_500 catalysts. The conversion of the BPA was analysed using HPLC and the mineralisation was analysed using a TOC analysis. The best experiment was performed with TNTs_500 + 10% GO composite, which can be attributed to the TiO2 crystalline structure obtained. According to the results obtained, TiO2 + 10% GO was found to exhibit the best degradation ratio, which can be ascribed to the fact that excessive GO can act as a charge carrier recombination centre and promotes the recombination of electron-hole pairs in reduced GO.
Keywords: heterogeneous photocatalysis, titanium dioxide, graphene oxide, bisphenol A
Published in RUNG: 23.02.2017; Views: 5726; Downloads: 289
.pdf Full text (2,96 MB)

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