Oxidation Of Acetone In Air Research Articles

Catalytic oxidation of acetone in air over Ag modified CeO2 catalysts under VUV irradiation: Comparison of different treatment process, performance, and mechanism studies

In this study, the performance of different treatment processes, including UV photolysis, ozonation, UV photolysis + ozonation, and vacuum ultraviolet (VUV) photolysis for oxidation of acetone in the presence and absence of Ag modified CeO2 photocatalysts was investigated. The as-synthesized catalysts were characterized using XRD, XPS, Raman Spectroscopy, BET, SEM, HRTEM, and EDX techniques. The attained data showed that by introducing Ag nanoparticles into the CeO2 network, the oxygen storage capability of the catalyst increases, which facilitates the generation of oxygen vacancies leading to the activation of lattice oxygen. The mechanism of the acetone oxidation and the contribution of each participating reaction mechanism were determined. The obtained results indicated that the VUV treatment system shows the best performance among different treatment processes, leading to more than 40% acetone conversion at room temperature. Moreover, the addition of Ag/CeO2 photocatalysts to the VUV treatment process not only increases the acetone conversion up to 76% but also, by involving the catalytic ozonation as a participating acetone oxidation pathway, can eliminate the generated ozone during the treatment process. The results revealed that adding Ag to CeO2 photocatalyst under VUV irradiation oxidized the produced CO, significantly improving the reaction selectivity and leading the acetone degradation reactions to total oxidation level of up to 96%. The stability of the Ag/CeO2 photocatalysts under VUV irradiation was investigated, and an in-situ regeneration process was employed for suppressing the catalyst deactivation process. The durability tests showed more than 73% acetone oxidation even after three consecutive runs and 990 min irradiation.

Highly photoreactive TiO2 hollow microspheres with super thermal stability for acetone oxidation

TiO2 hollow microspheres (TiO2-HMSs) have attracted much attention because of their high photoreactivity, low density, and good permeability. However, anatase TiO2-HMSs have poor thermal stability. In this study, surface-fluorinated TiO2-HMSs were assembled from hollow nanoparticles by the hydrothermal reaction of the mixed Ti(SO4)2–NH4HF–H2O2 solution at 180 °C. The effect of the calcination temperature on the structure and photoreactivity of the TiO2-HMSs was systematically investigated, which was evaluated by photocatalytic oxidation of acetone in air under ultraviolet irradiation. We found that after calcination at 300 °C, the photoreactivity of the TiO2-HMSs decreases from 1.39 × 10−3 min−1 (TiO2-HMS precursor) to 0.82 × 10−3 min−1 because of removal of surface-adsorbed fluoride ions. With increasing calcination temperature from 300 to 900 °C, the building blocks of the TiO2-HMSs evolve from truncated bipyramidal shaped hollow nanoparticles to round solid nanoparticles, and the photoreactivity of the TiO2-HMSs steady increases from 0.82 × 10−3 to 2.09 × 10−3 min−1 because of enhanced crystallization. Further increasing the calcination temperature to 1000 and 1100 °C results in a decrease of the photoreactivity, which is ascribed to a sharp decrease of the Brunauer–Emmett–Teller surface area and the beginning of the anatase–rutile phase transformation at 1100 °C. The effect of surface-adsorbed fluoride ions on the thermal stability of the TiO2-HMSs is also discussed.

Low-temperature hydrothermal synthesis of highly photoactive mesoporous spherical TiO 2 nanocrystalline

TiO 2 microspheres with mesoporous textural microstructures and high photocatalytic activity were prepared by hydrothermal treatment of mixed solution of titanium sulfate and urea with designed time. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N 2 adsorption–desorption measurements. The photocatalytic activity was evaluated via the photocatalytic oxidation of acetone in air at room temperature. The results show that the hydrothermal time significantly influences on the morphology, microstructure and photocatalytic activity of the as-prepared samples. With increasing hydrothermal time, specific surface areas and pore volumes decrease, contrarily, the crystallite size and relative anatase crystallinity increase. The photocatalytic efficiency of the as-prepared samples is obviously higher than that of commercial Degussa P25 (P25) powders. Especially, the as-prepared TiO 2 powders by hydrothermal treatment for 7 h shows the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2 times.

Preparation, characterization and visible-light-driven photocatalytic activity of Fe-doped titania nanorods and first-principles study for electronic structures

Fe-doped TiO2 (Fe-TiO2) nanorods were prepared by an impregnating-calcination method using the hydrothermally prepared titanate nanotubes as precursors and Fe(NO3)3 as dopant. The as-prepared samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption–desorption isotherms and UV–vis spectroscopy. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air under visible-light irradiation. The results show that Fe-doping greatly enhance the visible-light photocatalytic activity of mesoporous TiO2 nanorods, and when the atomic ratio of Fe/Ti (RFe) is in the range of 0.1–1.0%, the photocatalytic activity of the samples is higher than that of Degussa P25 and pure TiO2 nanorods. At RFe=0.5%, the photocatalytic activity of Fe-TiO2 nanorods exceeds that of Degussa P25 by a factor of more than two times. This is ascribed to the fact that the one-dimensional nanostructure can enhance the transfer and transport of charge carrier, the Fe-doping induces the shift of the absorption edge into the visible-light range with the narrowing of the band gap and reduces the recombination of photo-generated electrons and holes. Furthermore, the first-principle density functional theory (DFT) calculation further confirms the red shift of absorption edges and the narrowing of band gap of Fe-TiO2 nanorods.

Operando FTIR study of the photocatalytic oxidation of acetone in air over TiO 2–ZrO 2 thin films

Operando FTIR spectroscopy has been used to study the photocatalytic oxidation of acetone vapors over semiconductors films containing TiO 2 and ZrO 2. Preparation of these coatings was carried out by dipping a silicon wafer in stable sols containing particles of TiO 2, Ti 1− x Zr x O 2, or a mixture of ZrO 2 and TiO 2. These differences in chemical composition and phase homogeneity were selected in order to determine their effect on the photocatalytic performance. A transmission cell specifically designed for in situ studies of photocatalytic coatings was utilized for the FTIR experiments under reaction conditions. In contrast with investigations with powdered photocatalysts, the use of thin films guarantees that the whole semiconductor is irradiated, and for that reason purely photochemical reactions are monitored. Acetone adsorption takes place molecularly and is higher on the Ti 1− x Zr x O 2 coating. This fact is very likely related to the higher specific surface of the samples containing Zr. However, the maximum photocatalytic rate for acetone degradation corresponds to the films composed by a binary mixture of TiO 2 and ZrO 2. On the other hand, remarkable differences on the type and concentration of intermediates appearing as a result of the photocatalytic oxidation of acetone are found for the coatings studied. A simple kinetic model was applied to analyze the evolution of both gas phase and surface species. The parameters obtained indicate that each specific surface process is affected in a different way by the variation in the composition of the photoactive films.

Template‐Free Fabrication and Enhanced Photocatalytic Activity of Hierarchical Macro‐/Mesoporous Titania

AbstractHierarchical macro‐/mesoporous titania is prepared without the addition of templates or auxiliary additives at room temperature by the simple dropwise addition of tetrabutyl titanate to pure water, and then calcined at various temperatures. The products are characterized by X‐ray diffraction, N2‐adsorption–desorption analysis, scanning electron microscopy, and the corresponding photocatalytic activity is evaluated by measuring the photocatalytic oxidation of acetone in air. The results reveal that hierarchical macro‐/mesoporous structures of titania can spontaneously form by self‐assembly in alkoxide–water solutions in the absence of organic templates or auxiliary additives. The calcination temperature has a strong effect on the structures and photocatalytic activity of the prepared titania. At 300 °C, the calcined sample shows the highest photocatalytic activity. At 400 and 500 °C, the photocatalytic activity slightly decreases. When the calcination temperature is higher than 500 °C, the photocatalytic activity greatly decreases because of the destruction of the hierarchical macro‐/mesoporous structure of the titania and the drastic decrease of specific surface area. The hierarchically macro‐/mesostructured titania network with open and accessible pores is well‐preserved after calcination at 500 °C, indicating especially high thermal stability. The macroporous channel structures are even preserved after calcination at 800 °C. This hierarchical macro‐/mesostructured titania is significant because of its potential applications in photocatalysis, catalysis, solar‐cell, separation, and purification processes.

Photocatalytic activity of the calcined H-titanate nanowires for photocatalytic oxidation of acetone in air

Hydrogen titanate (H-titanate) nanowires were prepared via a hydrothermal reaction of TiO 2 powders (P25) in KOH solutions and then calcined at various temperatures. The phase structure, crystallite size, morphology, specific surface area, and pore structures of the calcined H-titanate nanowires at various temperatures were characterized with field emission scanning electron microscope, X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption isotherms, and their photocatalytic activities were evaluated by photocatalytic oxidation of acetone in air. With increasing calcination temperature, the specific surface area and porosity of the calcined samples steadily decreased. At a calcination temperature range of 400–600 °C, the calcined H-titanate nanowires showed higher photocatalytic activity than P25 powders for photocatalytic oxidation of acetone. Especially, at 500 °C, the calcined H-titanate nanowires showed the highest photocatalytic activity, which exceeded that of P25 by a factor of about 1.8 times. This can be attributed to the synergetic effect of larger specific surface area, higher pore volume and the presence of brookite TiO 2. With further increase in the calcination temperature (700–900 °C), the photocatalytic activity of the samples decreased obviously owing to the growth of TiO 2 crystallites.

Effects of Fe-doping on the photocatalytic activity of mesoporous TiO 2 powders prepared by an ultrasonic method

Highly photoactive nanocrystalline mesoporous Fe-doped TiO 2 powders were prepared by the ultrasonic-induced hydrolysis reaction of tetrabutyl titanate (Ti(OC 4H 9) 4) in a ferric nitrate aqueous solution (pH 5) without using any templates or surfactants. The as-prepared samples were characterized by thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), N 2 adsorption–desorption measurements, UV–visible adsorbance spectra (UV–vis) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by the photocatalytic oxidation of acetone in air. The results showed that all the Fe-doped TiO 2 samples prepared by ultrasonic methods were mesoporous nanocrystalline. A small amount of Fe 3+ ions in TiO 2 powders could obviously enhance their photocatalytic activity. The photocatalytic activity of Fe-doped TiO 2 powders prepared by this method and calcined at 400 °C exceeded that of Degussa P25 (P25) by a factor of more than two times at an optimal atomic ratio of Fe to Ti of 0.25. The high activities of the Fe-doped TiO 2 powders could be attributed to the results of the synergetic effects of Fe-doping, large BET specific surface area and small crystallite size.

Preparation and photocatalytic activity of mesoporous anatase TiO 2 nanofibers by a hydrothermal method

Mesoporous anatase TiO 2 nanofibers were prepared by a simple hydrothermal post-treatment of titanate nanotubes. The as-prepared samples were characterized with transmission electron microscopy (TEM), thermogravimetry (TG), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and N 2 adsorption–desorption measurement. The photocatalytic activity of the mesoporous TiO 2 nanofibers was evaluated by photocatalytic oxidation of acetone in air. The effects of hydrothermal post-treatment time on the structures and photocatalytic activity of the mesoporous TiO 2 nanofibers were discussed. The results showed that the photocatalytic activity of the TiO 2 nanofibers prepared by this method exceeded that of Degussa P25 when the hydrothermal post-treatment time was kept at 200 °C for 3–24 h. This could be attributed to the fact that the former had smaller crystallite size, larger specific surface area, and higher pore volume.

Effects of calcination temperature on the microstructures and photocatalytic activity of titanate nanotubes

Titanate nanotubes were prepared via a hydrothermal treatment of TiO 2 powders (P25) in a 10 M NaOH solution at 150 °C for 48 h and then calcined at various temperatures. The as-prepared titanate nanotubes before and after calcination were characterized with XRD, TEM, HRTEM, SEM, FESEM, and nitrogen adsorption–desorption isotherms. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic oxidation of acetone in air. The effects of calcination temperature on the phase structure, crystallite size, morphology, specific surface area, pore structures and photocatalytic activity of the titanate nanotubes were investigated. The results indicated that at 400 to 600 °C, the calcined nanotube samples showed a higher photocatalytic activity than Degussa P25. Especially, at 400 and 500 °C, the photocatalytic activity of the calcined nanotubes exceeded that of P25 by a factor of about 3.0 times. This could be attributed to the fact that the former had a larger specific surface area and pore volume. With further increase in the calcination temperature from 700 to 900 °C, the photocatalytic activity of the calcined nanotube samples greatly decreased due to the formation of rutile phase, the sintering and growth of TiO 2 crystallites and the decrease of specific surface area and pore volume.

Low-temperature preparation of nanocrystalline TiO 2 photocatalyst with a very large specific surface area

A facile method for obtaining highly photoactive bi-phase TiO 2 photocatalyst with a small crystalline size and very large specific surface area was developed. This was simply done by hydrolysis of titanium tetraisopropoxide (TTIP) in pure water at 70 °C and followed by drying at 100 °C. The prepared TiO 2 powder samples were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of the prepared TiO 2 powder slightly exceeded that of Degussa P25. This might be attributed to the fact that the prepared TiO 2 powder had a very large specific surface area (750 m 2 g −1) and small crystallite size (about 5 nm), but relative low crystallinity, comparing with Degussa P25 photocatalyst.

Preparation and photocatalytic activity of Fe-doped mesoporous titanium dioxide nanocrystalline photocatalysts

Fe-doped mesoporous titanium dioxide nanocrystalline photocatalysts were prepared by the sol–gel method. The as-prepared samples were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N 2 adsorption–desorption measurements. The photocatalytic activities were evaluated by photocatalytic oxidation of acetone in air. It was found that a small amount of Fe dopant in mesoporous TiO 2 powders could obviously enhance the photocatalytic activity, and when the atomic ratio of Fe/Ti was in the range of 0.05–0.25%, the photocatalytic activity of the samples was higher than that of Degussa P25 and un-doped mesoporous TiO 2 powders. This was ascribed to the fact that a small amount of Fe dopant reduced the recombination of photo-generated electrons and holes in the mesoporous TiO 2 powders during heterogeneous photocatalytic reaction.

Low Temperature Solvent Evaporation‐induced Crystallization Synthesis of Nanocrystalline TiO2 Photocatalyst

AbstractA novel and efficient methodology for obtaining highly active photocatalyst of bi‐phase TiO2 with small particle size and high specific surface area was developed by solvent evaporation‐induced crystallization (SEIC) method at low temperature. The prepared TiO2 powder was characterized with X‐ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of the TiO2 powder prepared by this method approached that of Degussa P25. This may be attributed to the fact that the prepared TIO2 powder had larger specific surface areas (265 nr2. g−1) and smaller crystallite size (about 5 nm), but relatively low crystallinity, as compared with Degussa P25.

Effects of acidic and basic hydrolysis catalysts on the photocatalytic activity and microstructures of bimodal mesoporous titania

Bimodal mesoporous titania powders with high photocatalytic activity were prepared by hydrolysis of titanium tetraisopropoxide in the presence of HNO 3 or NH 4OH under ultrasonic irradiation. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface areas, and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The effects of catalysts added during hydrolysis on the microstructure and photocatalytic activity of the TiO 2 powders were investigated. The results showed that HNO 3 enhanced the growth of brookite, while NH 4OH not only retarded phase transformation of the TiO 2 powders from amorphous to anatase and anatase to rutile but also suppressed the growth of brookite. All TiO 2 powders calcined from 400 to 600 °C showed bimodal pore-size distributions in the mesoporous region: one was intraaggregated pores with maximum pore diameters of ca. 4–9 nm and the other interaggregated ones with maximum pore diameters of ca. 35–50 nm. At 700 °C, the pore-size distributions of all samples exhibited monomodal distribution of the interaggregated pores due to the collapse of the intraaggregated pores. The photocatalytic activity of the TiO 2 powders prepared by this method and calcined at 400 °C exceeded that of Degussa P-25 when the molar ratio of HNO 3 or NH 4OH to H 2O was less than 0.05.

Preparation and characterization of highly photoactive nanocrystalline TiO2 powders by solvent evaporation-induced crystallization method

Highly photoactive bi-phase nanocrystalline TiO2 photocatalyst was prepared by a solvent evaporation-induced crystallization (SEIC) method, and calcined at different temperatures. The obtained TiO2 photocatalyst was characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results show that solvent evaporation can promote the crystallization and phase transformation of TiO2 at 100℃. When calcination temperatures are below 600℃, the prepared TiO2 powders show bimodal pore size distributions in the mesoporous region. At 700℃, the pore size distributions exhibit monomodal distribution of the inter-aggregated pores due to the collapse of the intra-aggregated pores. At 100℃, the obtained TiO2 photocatalyst by this method shows good photocatalytic activity, and at 400℃, its photocatalytic activity exceeds that of Degussa P25. This may be attributed to the fact that the prepared TiO2 photocatalyst has higher specific surface areas, smaller crystallite size and bimodal pore size distribution.

BASF incorporates sunblocker-grade TiO 2 in nylon fabric

A preliminary optical fiber reactor (OFR) that employs bare quartz fibers as a light-transmitting support of TiO2 was tested for gas treatment by investigating photocatalytic oxidation of acetone in air (50–750 ppmv). Using one or four TiO2-coated fibers in a continuous flow photoreactor, a steady-state conversion up to 80% was achieved at ambient temperature and pressure. The kinetic behavior of the acetone conversion in this study could be described by zero-order kinetics. The characteristics of coated-optical fibers were quantitatively analyzed and their use in photocatalytic gas treatment was discussed in detail. All the acetone molecules degraded was quantitatively converted to CO2 with no intermediates detected. No noticeable deactivation was observed within a few hours’ operation under the present experimental conditions. The conversion of acetone linearly increased with the incident light intensity without showing any sign of saturation. The transmitted light intensity through a TiO2-coated optical fiber exponentially decreased along the fiber, showing 90% extinction within 30 cm. The photocatalytic conversion measured as a function of the coated-fiber length showed a similar trend. An optimal coating thickness was found at around 1.5 μm above which the photocatalytic efficiency was reduced. The presence of water vapor reduced the reactivity due to the competitive adsorption on active surface site with acetone. While a measurable conversion of acetone was observed in the absence of O2, increasing O2 concentration up to 15% effectively enhanced the conversion.

Effects of F- Doping on the Photocatalytic Activity and Microstructures of Nanocrystalline TiO2 Powders

A novel and simple method for preparing highly photoactive nanocrystalline F--doped TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in a mixed NH4F−H2O solution. The prepared F--doped TiO2 powders were characterized by differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV−vis absorption spectroscopy, photoluminescence spectra (PL), transmission electron microscopy (TEM), and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the crystallinity of anatase was improved upon F- doping. Moreover, fluoride ions not only suppressed the formation of brookite phase but also prevented phase transition of anatase to rutile. The F--doped TiO2 samples exhibited stronger absorption in the UV−visible range with a red shift in the band gap transition. The photocatalytic activity of F--doped TiO2 powders prep...

Light-induced super-hydrophilicity and photocatalytic activity of mesoporous TiO 2 thin films

Transparent mesoporous TiO 2 (MTiO 2) and TiO 2 nanometer thin films were prepared on fused quartz via the modified reverse micellar and sol–gel methods. The MTiO 2 and TiO 2 films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray diffraction (XRD), BET surface area and UV–Vis spectrophotometry. The photoinduced super-hydrophilicity and photocatalytic activity of the films were evaluated by the water contact angle measurement and photocatalytic oxidation of acetone in air, respectively. It was found that MTiO 2 thin films at 500 °C showed higher photocatalytic activity and better light-induced hydrophilicity than the TiO 2 thin films. This is attributed to the following reasons: (1) MTiO 2 thin films are composed of smaller monodisperse spherical particles about 15 nm diameter, and possess more mesopores between spherical particles and higher surface areas and surface roughness, (2) the monodispersity of MTiO 2 particles was beneficial to the transfer and separation of photo-generated electrons and holes inside of and on the surface of TiO 2 particles, and reduced the recombination of photo-generated electrons and holes. At 900 °C, the MTiO 2 and TiO 2 films appeared to be in the rutile phase, but showed photoinduced hydrophilicity and no photocatalytic activity. This confirmed that the mechanism of photoinduced super-hydrophilicity of the films is different from that of photocatalytic oxidation.

Enhancing effects of water content and ultrasonic irradiation on the photocatalytic activity of nano-sized TiO 2 powders

A simple method for preparing highly photoactive nano-sized TiO 2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in pure water or the EtOH/H 2O mixed solution under ultrasonic irradiation. The prepared TiO 2 powders were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of TiO 2 powders prepared by this method from pure water or the EtOH/H 2O mixed solutions with the molar ratio of EtOH/H 2O=1 exceeded that of Degussa P-25. The molar ratios of EtOH/H 2O obviously influenced the crystallization, crystallite size, BET surface areas and photocatalytic activity of the prepared TiO 2 powders. Ultrasonic irradiation obviously enhanced the photocatalytic activity of TiO 2 powders whether the solvent is pure water or the EtOH/H 2O mixed solutions. This may be ascribed to the fact that ultrasonic irradiation enhances hydrolysis of titanium alkoxide and crystallization of TiO 2 gel.

Rapid synthesis of mesoporous TiO2 with high photocatalytic activity by ultrasound-induced agglomeration

Three-dimensional and thermally stable mesoporous TiO2 was synthesized without the use of any surfactants via treatment with high intensity ultrasound irradiation for a short period of time. Monodispersed TiO2 sol particles were formed initially by ultrasound-assisted hydrolysis of acetic acid-modified titanium isopropoxide. Then, the mesoporous spherical or globular particles, which have a narrow pore size distribution, were produced by controlled condensation and agglomeration of these sol nanoparticles under high intensity ultrasound irradiation. The mesoporous TiO2 was characterized by XRD, TEM, nitrogen adsorption, TGA/DTA and FTIR. Low-angle XRD and TEM show the mesoporous TiO2 has a wormhole-like structure and a lack of long-range order. Nitrogen adsorption results indicate that the mesoporous TiO2 retains mesoporosity with a narrow pore size distribution and high surface area to at least 673 K. The thermal stability of mesoporous TiO2 is attributed to its thick inorganic walls, consisting of TiO2 nanoparticles. TGA study shows that this synthetic method is environmentally friendly. The photocatalytic activity of mesoporous TiO2 for the oxidation of acetone in air was measured. As-prepared mesoporous TiO2 has negligible activity due to its amorphous structure. Calcined mesoporous TiO2 shows better activity than commercial photocatalyst P25. The reasons for the high activity of mesoporous TiO2 are discussed.