Photocatalytic Activity Of Mesoporous TiO Research Articles

Physical Adsorption and Photocatalytic Activity of Titanium Dioxide Nanotube and Graphene Oxide Composite

In this study, we synthesized graphene oxide (GO) by modified low temperature Hummer’s method and in situ hydrothermally grown TiO­2 nanotube (TNT) onGO sheet. Transmission electron microscopic (TEM) images showed the homogeneous formation of TNT with the mean diameter of ~8 nm and the co-existence of TNT and GO in the composite sample. X-ray differaction pattern of GO indicated the successful fabrication. The UV-vis measurement with methylene blue indicated the improvement of physical adsorption of the composite samples.
 Keywords
 TNTs, GO, physical adsorption, composite
 References
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Preparation and Photocatalytic Activity of Mesoporous TiO2 Photocatalyst Co‐doped with Fe and H3PW12O40

AbstractThe mesoporous titanium dioxide (MTiO2) photocatalysts co‐doped with Fe and H3PW12O40 were synthesized by template method using tetrabutyl titanate (Ti(OC4H9)4), Fe(NO3)k39H2Oand H3PW12O40 as precursors and Pluronic P123 as template. The as‐prepared photocatalyst was characterized by N2 adsorption‐desorption measurements, X‐ray diffraction (XRD), scanning electron microscopy (SEM) and UV‐vis adsorption spectroscopy, and the photocatalytic activities of the prepared samples under UV and visible light were estimated by measuring the degradation rate of methyl blue (MB) (50 mg/L) in an aqueous solution. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of ca. 10 nm with high surface area of ca. 150 m2/g. The results of MB photodecomposition showed that co‐doped mesoporous TiO2 exhibited higher photocatalytic activities than un‐doped, single‐doped mesoporous TiO2 under UV and visible light irradiation. It was shown that the co‐doped MTiO2 could be activated by visible light and could thus be used as an effective catalyst in photo‐oxidation reactions. The synergistic effect of Fe and H3PW12O40 co‐doping played an important role in improving the photocatalytic activity.

Synthesis, Characterizations and Photocatalytic Activity of Mesoporous TiO<sub>2</sub> Using Typha Latifolia as Template

Typha latifolia were successfully used as template to synthesize mesoporous titania and silica with efficient photocatalytic activity under solar and visible light. Both two titania and silica samples were characterized by a combination of various physicochemical techniques, such as, N2 adsorption/ desorption isotherm, diffuse reflectance UV-vis, and X-ray diffraction. It was found that both two synthesized samples exhibited similar morphologies to the original templates. The presence of the residual carbon species of mesoporous titania and silica strongly affects their photocatalytic activity. The photoactivity of P25 TiO2 could not almost exhibit while both mesoporous titania and silica samples exhibited varied photoactivities for dyes under visible light, due to the presence of the residual carbon species. Moreover, as a whole the titania sample enhanced the higher photocatalytic activity than the silica sample under both solar and visible light.

Preparation, Characterization, and Photocatalytic Activity of Mesoporous TiO<SUB>2</SUB> Thin Films

Cubic-based ordered mesoporous TiO2 thin films were prepared by an evaporation-induced self-assembly method through a carefully controlling the hydrolysis/condensation conditions. The obtained sample exhibits mesoporous structure with a narrow pore size distribution. The TiO2 thin films have thick inorganic walls composed of nanocrystalline anatase. A reasonable explanation is also proposed to elucidate the formation of thick and stable mesoporous TiO2 films. The mesoporous TiO2 exhibits good photocatalytic activity. Nearly all the methyl orange has been degraded by the mesoporous TiO2 calcined at 500 degrees C.

Improving the visible light photocatalytic activity of mesoporous TiO 2 via the synergetic effects of B doping and Ag loading

B-doped together with Ag-loaded mesoporous TiO 2 (Ag/B–TiO 2) was prepared by a two-step hydrothermal method in the presence of boric acid, triblock copolymer surfactant, and silver nitrate, followed by heat treatment. The obtained samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption. It was revealed that all samples consist of highly crystalline anatase with mesoporous structure. For Ag/B–TiO 2, B was doped into TiO 2 matrix in the form of both interstitial B and substitutional B while Ag was deposited on the surface of B–TiO 2 in the form of metallic silver. Compared with the single B-doped or Ag-loaded TiO 2 one, mesoporous Ag/B–TiO 2 exhibits much higher visible light photocatalytic activity for the degradation of Rhodamine 6G, which can be ascribed to the synergistic effects of B doping and Ag loading by narrowing the band gap of the photocatalyst and preventing the fast recombination of the photogenerated charge carriers, respectively.

Enhanced photocatalytic activity of mesoporous TiO2aggregates by embedding carbon nanotubes as electron-transfer channel

Mesoporous multiwalled carbon nanotubes/titanium dioxide (CNTs/TiO(2)) nanocomposites with low loading amounts (0-0.5 wt%) of CNTs embedded inside mesoporous TiO(2) aggregates has been prepared by a simple one-pot hydrothermal method using titanium sulfate as titanium source. The as-prepared CNTs/TiO(2) samples are carefully characterized, analyzed and discussed. In contrast to previous reports with high CNT loading, our results indicate that a low CNT loading slightly influences the textural properties (including crystallite size, degree of crystallinity, specific surface areas, and pore volume etc.) and UV-light absorption of the mesoporous TiO(2) aggregates. The SEM and TEM results demonstrate that the CNTs are mostly embedded in the mesoporous TiO(2) aggregates. Moreover, chemical bonds are formed at the interface between CNTs and TiO(2), which is confirmed by the Raman, IR and XPS analyses. Significantly, we point out that PL analysis in terms of intensity of PL signals seems to not be a reliable way to monitor the recombination rate in the CNTs/TiO(2) composite, due to the quenching effect of CNTs. Instead, the analysis of transient photocurrent responses is introduced, which definitely reflects CNTs as fast electron transfer channels in chemically-bonded CNTs/TiO(2) composites with low CNT loading. Notably, the positive synergy effects of CNTs and TiO(2) depend on both the CNT loading amount and the state of interfacial contacts. In our study, only these chemically bonded CNTs/TiO(2) nanocomposites with appropriate loading amounts (<0.1 wt%) favor the separation of photogenerated electron-hole pairs and decrease their recombination rate and thus display significantly enhanced photocatalytic activity for degrading acetone in air under UV irradiation, as compared with pristine TiO(2) counterparts and commercial P25 photocatalyst. In contrast, a high CNT loading (>0.1 wt%) results in a decrease in photocatalytic activity; a simple mechanical mixing of CNTs and TiO(2) without forming chemical bonds at the interface also results in inferior photocatalytic performance.

Synthesis of mesoporous TiO 2 in aqueous alcoholic medium and evaluation of its photocatalytic activity

Mesoporous TiO 2 was synthesized using triblock copolymer as the structure directing template in ethanol/water, isopropanol/water or 1-butanol/water medium by sol–gel method. The presence of intense peak at low angle in the XRD patterns confirmed the orderly arrangement of mesopores in the material. Among the three different alcohols, ethanol had influenced better in controlling the particle size than others. The enhanced specific surface area also revealed the formation of mesopores. Aggregates of particles were clearly seen in the TEM images and the size of the particles was approximately 10 nm. The photocatalytic activity of mesoporous TiO 2 was evaluated using aqueous alachlor as a model pollutant. The activity of mesoporous TiO 2 synthesized in ethanol/water mole ratio of 50 was higher than other mesoporous TiO 2 and commercial TiO 2 (Degussa P-25). The transport of excited electrons from one particle to its neighboring nanoparticles of mesoporous TiO 2 is suggested to be the cause for enhanced photocatalytic activity.

Microstructure and photocatalytic activity of mesoporous TiO 2 film coated on an aluminum foam

A TiO 2 film was synthesized via a surfactant assisted sol–gel process and dip-coated on the surface of an open-celled aluminum foam. The film shows a typical mesoporous structure composed of anatase crystalline grains with the average size of 10 nm, and has the thickness of about 3.5 μm as well as the BET surface area of 78.1 m 2/g. It exhibits high photocatalytic efficiency toward the decomposition of formaldehyde at continuous flow mode. The relatively small grain size of TiO 2 and relatively thick mesoporous structure, which is favorable for high photochemical activity and the mass transfer of the reactants, should be responsible for the properties.

Synthesis of hollow microcapsules using SBA-15 sol and their evaluation as a photocatalyst in the decomposition of methyleneblue

A simple and useful route to synthesize mesoporous TiO 2 microcapsules with a hollow macro-core structure was studied. The deposition of hydrophilic precursor sol containing surfactants in the hydrophobic solvents onto the monodispersed polymer surfaces has been applied to produce the mesoporous shells after calcination. Photocatalytic activity of mesoporous TiO 2 was evaluated in aqueous phase degradation of methyleneblue as a test reaction.

Enhanced photocatalytic activity of mesoporous TiO 2 with MgO coating

To improve the photocatalytic activity of TiO 2 on decomposing anionic surfactants, MgO-coated mesoporous TiO 2 was fabricated by evaporation induced self-assembly (EISA) combined with impregnation method. MgO was uniformly dispersed on the surface of TiO 2, which played the role of stabilizing the ordered mesostructure of TiO 2 and improving the adsorption of anion surfactants, while inhibiting the crystallization of TiO 2. The powders coated with 5 wt.% MgO showed the highest photocatalytic activity for the decomposition of sodium dodecylbenzenesulfonate-6 ( DBS).

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.

Synergistic Effects of B/N Doping on the Visible‐Light Photocatalytic Activity of Mesoporous TiO2

Die Autoren dieser Zuschrift möchten nachträglich zwei zusätzliche Beiträge zitieren. Sowohl Fornasiero et al.23a als auch Sun et al.23c haben B,N-dotiertes TiO2 beschrieben. Die Stickstoffdotierung wurde dabei aber nicht durch thermische Behandlung in einer Ammoniakatmosphäre, sondern auf nasschemischem Weg erzielt, und es wurden keine B-N-Bindungen gebildet. Das vollständige Literaturzitat 23 ist hier aufgeführt.

Synergistic Effects of B/N Doping on the Visible‐Light Photocatalytic Activity of Mesoporous TiO2

Add an N: The visible-light absorption of boron-doped mesoporous TiO2 depends strongly on the state of the dopant (see picture), although the activity can be substantially enhanced by additional doping of nitrogen. The new O-Ti-B-N structure formed on the surface of the photocatalyst is highly active in collecting and separating the charge carriers, thereby greatly enhancing the visible light photocatalytic activity.

Synergistic Effects of B/N Doping on the Visible‐Light Photocatalytic Activity of Mesoporous TiO2

N zusetzen: Die Absorption von bordotiertem mesoporösem TiO2 im sichtbaren Bereich hängt stark vom Dotierungszustand ab und kann durch gleichzeitige Dotierung mit Stickstoff erhöht werden. Durch die neuen O-Ti-B-N-Oberflächenstrukturen (siehe Bild) kann der Photokatalysator Ladungsträger hoch aktiv sammeln und separieren, und die photokatalytische Aktivität bei Bestrahlung mit sichtbaren Licht ist deutlich verbessert. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2008/z705633_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The structural, physical and photocatalytic properties of the mesoporous Cr-doped TiO 2

A visible-light-active mesoporous Cr-doped TiO 2 photocatalyst with worm-like channels was synthesized using an evaporation-induced self-assembly approach and characterized by X-ray powder diffraction, nitrogen adsorption–desorption, X-ray photoelectron spectroscopy, transmission electron microscope, and UV–vis diffuse reflectance, respectively. The effect of Cr 3+ doping concentration on the photocatalytic activity of mesoporous TiO 2 was investigated from 0.1 to 1 mol%. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of about 8 nm with high surface area of 117 m 2/g and a crystalline anatase pore wall doped by Cr 3+. Compared with pure mesoporous TiO 2, the Cr-doped TiO 2 extended the photoabsorption edge into the visible light region. The results of gaseous acetaldehyde photodecomposition showed that mesoporous Cr-doped TiO 2 exhibited higher photocatalytic activities than pure mesoporous TiO 2 and nonporous Cr-doped TiO 2 under visible light irradiation.

Microstructure characterization and photocatalytic activity of mesoporous TiO 2 films with ultrafine anatase nanocrystallites

A series of mesoporous TiO 2 films on borosilicate glass with ultrafine anatase nanocrystallites were successfully synthesized using a non-acidic sol gel preparation route, which involves the use of nonionic surfactant Tween 20 as template through a self assembly pathway. The microstructure of these TiO 2 films was characterized by XRD, SEM, HR-TEM, UV–Vis spectroscopy, and N 2 adsorption–desorption isotherm analysis. Their photocatalytic activities were investigated by using creatinine as a model organic contaminate in water. It was found that all mesoporous TiO 2 films prepared with Tween 20 exhibited a partially ordered mesoporous structure. The photocatalytic activity of the TiO 2 films could be remarkably improved by increasing Tween 20 loading in the sol at the range of 50% (v/v), which yielded large amount of catalyst (anatase) on the glass support and enhanced specific surface area. The optimum Tween 20 loading was 50% (v/v) in the sol, above which good adhesion between TiO 2 films and borosilicate glass could not be maintained. The final TiO 2 film (Tween 20: final sol = 50%,v/v) exhibits high BET surface area (∼ 120 m 2/g) and pore volume (0.1554 cm 3/g), ultrafine anatase nanocrystallinity (7 nm), uniform and crack free surface morphology, and improved photocatalytic activity.

Synthesis and photocatalytic activity of mesoporous TiO 2 with the surface area, crystallite size, and pore size

Mesoporous TiO 2 materials with various pore-size distributions were synthesized by using diblock copolymers via a sol–gel process in aqueous solution. The properties of these materials were characterized by FE-SEM, HR-TEM, XRD, DRS, BET, and BJH analysis. All particles have spherical morphology with a diameter range of 1–3 μm. The mesoporous TiO 2 materials calcined at 400 °C were found to have different specific surface areas—186, 210, and 192 m 2 g −1—and average pore sizes depending on the type of diblock copolymer—5.1, 6.1, and 6.4 nm—and their crystallite sizes were found to be 8.1, 8.3, and 8.8 nm. The photocatalytic activity of each sample was investigated by measuring the photodecomposition of methylene blue (MB), and the small crystallite size, large surface area, and small pore size were found to exhibit better photocatalytic activities. In addition, the photocatalytic activities of all the mesoporous TiO 2 materials were found to be better than that of commercial TiO 2.

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.

Preparation and photocatalytic activity of mesoporous TiO 2 derived from hydrolysis condensation with TX-100 as template

Mesoporous titania powder was prepared by hydrolysis condensation process using a non-ionic surfactant Triton X-100 (TX-100) as template. The template could be easily removed by washing the precipitation with water and ethanol at room temperature as confirmed by FT-IR. XRD pattern demonstrates that as-synthesized product had a framework of anatase phase. TEM image shows the product possessed disordered nanopore channels and HRTEM shows the framework consisted of crystalline particles. N 2 adsorption–desorption analysis indicates that the as-synthesized sample had a BET surface area of 241 m 2/g and a narrow pore size distribution centered at 4.9 nm. The mesoporous titania could efficiently degrade methyl orange under UV irradiation and showed a stronger photocatalytic activity than commercial titania P25. Effects of calcination on crystallinity, pore structure and photocatalytic activity were also studied.