1. Development and characterization of improved materials for antifouling applicationsUrška Lavrenčič Štangar, Iztok Arčon, Tihana Čižmar, 2015, published scientific conference contribution abstract Found in: ključnih besedah
Summary of found: ...method, photocatalysis, hybrid materials, Cu K-edge XANES, photocatalytic activity...
Keywords: sol-gel method, photocatalysis, hybrid materials, Cu K-edge XANES, photocatalytic activity
Published: 15.02.2016; Views: 3024; Downloads: 0
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2. Thermal properties of surface-modified [alpha] and [epsilon]-Fe [sub] 2O [sub] 3 photocatalysts determined by beam deflection spectroscopyFernando Fresno, Mladen Franko, Dorota Korte, Giorgio Carraro, 2014, published scientific conference contribution Found in: ključnih besedah
Summary of found: ... photocatalytic activity, photothermal beam deflection spectroscopy, thin films,...
Keywords: photocatalytic activity, photothermal beam deflection spectroscopy, thin films
Published: 16.06.2016; Views: 3015; Downloads: 118
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5. Chemical structure in Cu-modified TiO2-SiO2 nanocomposites calcined at 500 °C for 1 h in airT. Čižmar, Iztok Arčon, Urška Lavrenčič Štangar, 2017, published scientific conference contribution abstract Found in: ključnih besedah
Summary of found: ...dioxide, metal doping, Cu K-edge XANES, EXAFS, photocatalytic activity...
Keywords: Cu-modified TiO2-SiO2 photocatalysts, titanium dioxide, metal doping, Cu K-edge XANES, EXAFS, photocatalytic activity
Published: 22.08.2017; Views: 12199; Downloads: 0
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6. Correlations between photocatalytic activity and chemical structure of Cu-modified TiO2-SiO2 nanoparticle compositesT. Čižmar, doctoral dissertation Abstract: The objective of this dissertation was to examine how copper modification can improve the photocatalytic activity of TiO2-SiO2 and to explain the correlation between Cu concentration and chemical state of Cu cations in the TiO2-SiO2 matrix, as well as the photocatalytic activity under the UV/solar irradiation.
The Cu-modified TiO2-SiO2 photocatalysts were prepared by a low temperature sol-gel method based on organic copper, silicon and titanium precursors with varied Cu concentrations (from 0.05 to 3 mol%). The sol-gels were dried at 150 °C to obtain the photocatalysts in the powder form. To test thermal stability, additional set of photocatalysts was obtained by calcinating dried samples in air at 500 °C for 1 h.
The photocatalytic activity was determined by a fluorescence-based method of terephthalic acid decomposition. Up to three times increase in photocatalytic activity of air-dried samples is obtained when TiO2-SiO2 matrix is modified with Cu in a narrow concentration range from 0.05 to 0.1 mol%. At higher Cu loadings the photocatalytic activity of Cu-modified photocatalyst is smaller than in the unmodified reference TiO2-SiO2 photocatalyst. Calcined samples showed significantly reduced photocatalytic activity compared to air-dried samples.
XRD analysis showed that all Cu-modified TiO2-SiO2 nanocomposites with different Cu concentrations have the same crystalline structure as unmodified TiO2-SiO2 nanocomposites (air-dried or calcined). The addition of Cu does not change the relative ratio between the anatase and brookite phase or unit cell parameters of the two TiO2 crystalline structures. TEM analysis showed that the addition of Cu does not change the morphology of TiO2-SiO2 catalyst dried at 150 °C.
The Cu K-edge XANES and EXAFS analysis were used to determine valence state and local structure of Cu cations in Cu-modified TiO2-SiO2 photocatalyst. The results elucidate the mechanism responsible for the improved or hindered photocatalytic activity. In the air-dried samples with low Cu content, which exhibit largest activity, Cu-O-Ti connections are formed, suggesting that the activity enhancement is due to Cu(II) cations attachment on the surface of the photocatalytically active TiO2 nanoparticles, so Cu(II) cations may act as free electron traps, reducing the intensity of recombination between electrons and holes at the TiO2 photocatalyst’s surface. At higher Cu loadings no additional Cu-O-Ti connections are formed, instead only Cu-O-Cu connections are established, indicating the formation of amorphous or nanocrystalline Cu(II) oxide, which hinders the photocatalytic activity of TiO2. Calcination of Cu-modified TiO2-SiO2 photocatalysts at 500 °C induces significant structural changes: Cu-O-Ti connections are lost, Cu partially incorporates into the SiO2 matrix and amorphous copper oxides, which again reduce the photocatalytic activity of the material, are formed.
Found in: ključnih besedah
Keywords: titanium dioxide, Cu-modified TiO2-SiO2 photocatalyst, photocatalytic activity, Cu K-edge XANES, EXAFS.
Published: 17.12.2018; Views: 2235; Downloads: 85
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7. Improved photocatalytic activity of anatase-rutile nanocomposites induced by low-temperature sol-gel Sn-modification of TiO2Ksenija Maver, Iztok Arčon, Urška Lavrenčič Štangar, Mattia Fanetti, Saim Emin, Matjaž Valant, 2020, original scientific article Abstract: The Sn-modified TiO2 photocatalysts are prepared by low-temperature sol-gel processing based on organic titanium
and tin precursors with varied Sn concentrations (from 0.1–20 mol .%). The role of Sn dopant as the
promotor of the formation of TiO2 rutile crystalline phase is explained and the optimal Sn concentration for
preparation of efficient Sn-modified titania photocatalyst is determined. Up to 40 % increase in photocatalytic
activity is achieved in Sn-modified TiO2 photocatalytic thin films dried at 150 °C with low Sn concentrations in
the range from 0.1 to 1 mol .%. At low Sn concentrations optimal ratio between anatase and rutile (nano)crystals
is obtained, which facilitates charge separation at the TiO2 photocatalyst’s surface. When the concentration of Sn
increases above 5 mol.% or when the films are calcined at 500 °C, the relative amount of rutile phase with
inferior photocatalytic activity, increases and the nanocrystals of titania grow, leading to fewer active sites per
unit mass and the reduction of activity in comparison to unmodified TiO2.
Found in: ključnih besedah
Keywords: Anatase-rutile
Sn-modified TiO2
XAS analysis
Photocatalytic activity
Published: 10.02.2020; Views: 1232; Downloads: 0
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8. Sn-modified TiO[sub]2 thin film photocatalysts prepared by low-temperature sol-gel processingKsenija Maver, 2021, doctoral dissertation Abstract: Due to many advantageous physiochemical properties, titanium dioxide (TiO2) is the most widely used photocatalyst in numerous applications, such as wastewater treatment and air purification, self-cleaning surfaces and energy conversion (H2 generation). However, one of its disadvantages is the high electron-hole recombination rate, and coupling with other semiconductors is one of the strategies to improve it. The objective of this dissertation was to investigate how the photocatalytic activity of pure TiO2 can be improved by tin modification and to explain the mechanism of increased or hindered photoactivity in correlation with the structural properties of the modified TiO2 photocatalysts.
A new low-temperature sol-gel synthesis route was developed to prepare Sn- or SnO2-modified TiO2 photocatalysts. In both cases, organic tin and titanium precursors were used. Tin in the form of Sn cations was used to prepare Sn-modified TiO2. In this case, the precursors went through the sol-gel reaction together to form a Sn-TiO2 sol. In the case of SnO2 modification, the SnO2 sol was prepared separately and additionally mixed with the TiO2 sol to form a TiO2/SnO2 bicomponent semiconductor system. Different molar ratios of tin to titanium were prepared to investigate the correlation between the tin concentration and the photocatalytic properties of the photocatalysts in the form of thin films. The results were used to optimize the synthesis conditions to obtain an improved activity of the modified TiO2 photocatalysts under UV-irradiation.
The photocatalytic activity of the thin films was determined by measuring the degradation rate of an azo dye. An increase of up to 40 % in the photocatalytic activity of the dried samples (at 150 °C) was achieved when the TiO2 was modified with the Sn or SnO2 in a concentration range of 0.1 to 1 mol.%. At higher Sn or SnO2 loadings and after calcination of the samples at 500 °C, the photocatalytic activity of the photocatalyst was reduced compared to the unmodified TiO2.
Different characterization techniques (UV-Vis, XRD, nitrogen physisorption, TEM, SEM and XAS) were employed to clarify the mechanism responsible for the enhanced and hindered photocatalytic performance of the Sn- and SnO2-modified TiO2 photocatalysts. The results showed that a nanocrystalline structure is already achieved in the samples by the low-temperature film treatment (drying at 150 °C) and that the photocatalytic efficiency is mainly influenced by the crystalline phase composition: anatase/rutile in the case of Sn-modified and TiO2/SnO2 in the case of SnO2-modified TiO2. The crystal size and specific surface area differ insignificantly between the equally thermally treated samples and partly explain the differences in photoefficiency of the calcined samples compared to the dried samples. The structural study at the atomic level, using the Sn K-edge EXAFS, revealed that Sn cations act as nucleation sites for the anatase to rutile transformation in the Sn-modified TiO2 photocatalysts, while in the SnO2-modified TiO2 samples the nanocrystalline cassiterite SnO2 is bound to the TiO2 nanocrystallites via the Sn-O-Ti bond. In both cases, the advantage of coupling the two semiconductors was achieved by separating the charge carriers and thus prolonging their lifetime for accessibility to participate in the redox reactions. The maximum activity enhancement was achieved in the low concentration range (0.1–1 mol.%), which means that an optimal ratio and contact of the two phases are obtained for the given physical parameters, such as particle size, shape and specific surface area of the catalyst.
Found in: ključnih besedah
Summary of found: ...this dissertation was to investigate how the photocatalytic activity of pure TiO2 can be improved...
Keywords: Sn-modified TiO2, SnO2-modified TiO2, low-temperature sol-gel, thin films, photocatalytic activity, anatase/rutile system, Sn K-edge EXAFS, dissertations
Published: 09.06.2021; Views: 592; Downloads: 42
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9. Improved photocatalytic activity of SnO[sub]2-TiO[sub]2 nanocomposite thin films prepared by low-temperature sol-gel methodUrška Lavrenčič Štangar, Giovanni Palmisano, Matjaž Valant, Mattia Fanetti, Samar Al Jitan, Iztok Arčon, Ksenija Maver, 2021, original scientific article Abstract: The objective of this research was to investigate how the photocatalytic activity of pure TiO2 can be improved by
SnO2 modification. Different molar ratios of tin to titanium were prepared. The correlation between tin concentration
and structural properties was investigated to explain the mechanism of photocatalytic efficiency and
to optimize the synthesis conditions to obtain enhanced activity of the SnO2-modified TiO2 photocatalysts under
UV-irradiation. The SnO2-modified TiO2 photocatalysts were prepared by a low-temperature sol-gel method
based on organic tin and titanium precursors. The precursors underwent sol-gel reactions separately to form
SnO2-TiO2 sol. The sol-gels were deposited on a glass substrate by a dip-coating technique and dried at 150 ◦C to
obtain the photocatalysts in the form of a thin film. To test the thermal stability of the material, an additional set
of photocatalysts was prepared by calcining the dried samples in air at 500 ◦C. The photocatalytic activity of the
samples was determined by measuring the degradation rate of an azo dye. An increase of up to 30% in the
photocatalytic activity of the air-dried samples was obtained when the TiO2 was modified with the SnO2 in a
concentration range of 0.1–1 mol.%. At higher SnO2 loadings, the photocatalytic activity of the photocatalyst
was reduced compared to the unmodified TiO2. The calcined samples showed an overall reduced photocatalytic
activity compared to the air-dried samples. Various characterization techniques (UV-Vis, XRD, N2-physisorption,
TEM, EDX, SEM, XAS and photoelectrochemical characterization) were used to explain the mechanism for the
enhanced and hindered photocatalytic performances of the SnO2-modified TiO2 photocatalysts. The results
showed that the nanocrystalline cassiterite SnO2 is attached to the TiO2 nanocrystallites through the Sn-O-Ti
bonds. In this way, the coupling of two semiconductors, SnO2 and TiO2, was demonstrated. Compared to
single-phase photocatalysts, the coupling of semiconductors has a beneficial effect on the separation of charge
carriers, which prolongs their lifetime for accessibility to participate in the redox reactions. The maximum increase
in activity of the thin films was achieved in the low concentration range (0.1–1 mol.%), which means that
an optimal ratio and contact of the two phases is achieved for the given physical parameters such as particle size,
shape and specific surface area of the catalyst.
Found in: ključnih besedah
Keywords: photocatalytic activity, Sn-modified TiO2, low-temperature, thin films, XAS analysis
Published: 05.07.2021; Views: 292; Downloads: 0
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