Co-doped Mesoporous TiO2 Research Articles

Enhancement of Visible-Light Photocatalytic Degradation of Tetracycline by Co-Doped TiO2 Templated by Waste Tobacco Stem Silk.

In this study, Co-doped TiO2 was synthesized using waste tobacco stem silk (TSS) as a template via a one-pot impregnation method. These samples were characterized using various physicochemical techniques such as N2 adsorption/desorption analysis, diffuse reflectance UV-visible spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and electron paramagnetic resonance spectroscopy. The synthesized material was used for the photodegradation of tetracycline hydrochloride (TCH) under visible light (420-800 nm). No strong photodegradation activity was observed for mesoporous TiO2 synthesized using waste TSS as a template, mesoporous Co-doped TiO2, or TiO2. In contrast, Co-doped mesoporous TiO2 synthesized using waste TSS as a template exhibited significant photocatalytic degradation, with 86% removal of TCH. Moreover, owing to the unique chemical structure of Ti-O-Co, the energy gap of TiO2 decreased. The edge of the absorption band was redshifted, such that the photoexcitation energy for generating electron-hole pairs decreased. The electron-hole separation efficiency improved, rendering the microstructured biotemplated TiO2 a much more efficient catalyst for the visible-light degradation of TCH.

Facile Preparation of N/F Co-Doped Mesoporous TiO2 vis-Photocatalyst based on a Bi-Functional Template

Developing nonmetal-doped mesoporous TiO2 is highly attractive for preparing semiconductor visible photocatalyst with high activities. Here, we prepare N/F co-doped mesoporous TiO2 with high vis-photocatalytic activities by a simple liquid phase deposition process followed by annealing in air using C[Formula: see text]TAB as a bi-functional template (forming mesoporous and providing dopants). N2 adsorption isotherms, low-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate the formation of wormhole-like mesoporous structure. Wide-angle XRD and high-resolution TEM demonstrate the presence of anatase TiO2 mesopore wall. XPS analyses reveal that N is doped into TiO2 lattice in the forms of substitutional and interstitial N species, and that F is doped into the TiO2 lattice in the form of interstitial F. The mesopore-forming and doping mechanisms are thoroughly discussed based on the bi-function of C[Formula: see text]TAB template. Mesoporous structure results in a high BET surface area of TiO2. High-concentration nitrogen species in anatase lattice and mesoporous structure remarkably increase the visible absorption of TiO2. As a result, the reaction rate constant of MB degradation catalyzed by N/F co-doped mesoporous TiO2 photocatalysts is about 7 times that by P25.

Zn and Sr co-doped TiO2 mesoporous nanospheres as photoanodes in dye sensitized solar cell

Mesoporous TiO2 nanospheres that were co-doped with Zn and Sr were synthesized via a simple hydrothermal method. These materials were used as the photoanode in dye-sensitized solar cells (DSSCs). Field-emission electron microscopy showed that the nanospheres were monodisperse and interconnected, while transmission electron microscopy (TEM) showed that the nanospheres were composed of different nanostructures (nanotubes, diamond and sheet-like structures). Scanning TEM showed a homogeneous distribution of Sr, Ti, Zn and O throughout the nanospheres. When the Zn, Sr co-doped mesoporous TiO2 nanospheres were incorporated into DSSCs, a device efficiency of 4.6%, a short circuit photocurrent density of 8.63 mA cm−2 and an open circuit voltage 0.72 V were achieved. The efficiencies of these devices were higher than that of a comparison device (2.9%) that contained TiO2 (P25).

Preparation and Photocatalytic Properties of Co and N Co-doped Mesoporous TiO2

Preparation and Photocatalytic Properties of Co and N Co-doped Mesoporous TiO2

Enhanced photocatalytic degradation of rhodamine B under visible light irradiation on mesoporous anatase TiO2 microspheres by codoping with W and N

Mesoporous anatase TiO2 microspheres were prepared via solvothermal method. Ammonium tungstate was used as the W source, and ammonia gas flowing in an ammonothermal reactor as the N source for codoping. TiO2:(W,N) mesoporous microspheres, which were prepared from solvothermal treatment at 160 °C for 16 h and thermal ammonolysis at 500 °C for 2 h after calcination, have high specific surface area of 106 m2 g−1. XPS results indicate the presence of NO, Ni and W6+ in the codoped mesoporous TiO2 microspheres. Monodoping with N shifts the absorption band edge of anatase TiO2 from ultraviolet region to visible region. Although codoping with W makes the visible light absorbance decrease a little, the photocatalytic degradation of a cationic dye rhodamine B (RhB) on mesoporous TiO2:(W,N) microspheres is increased to 1.7 times of that on mesoporous TiO2:N microspheres. This may due to decreasing recombination centers by W-doping charge compensation.

Enhanced photocatalytic activity of nitrogen and indium co-doped mesoporous TiO2 nanocomposites for the degradation of 2,4-dinitrophenol under visible light

Mesoporous N/In2O3–TiO2 nanocomposite photocatalysts were synthesized by sol-gel route using Pluronic P123 as the structure directing template. The synthesized composite materials were successfully characterized by X-ray powder diffraction, high resolution transmission electron microscopy, N2 adsorption–desorption studies, X-ray photoelectron spectroscopy, diffuse reflectance UV–vis spectroscopy, Fourier transform infrared spectroscopy and photoluminescence spectroscopy. The photocatalytic activities of all the synthesized catalysts were evaluated for the degradation of 2,4-dinitrophenol under visible light irradiation. The results demonstrated that the mesoporous N/In2O3–TiO2 showed higher efficiency than meso TiO2, N-TiO2 and In2O3–TiO2 under visible light irradiation and the optimum molar ratio of N and In to Ti is 0.3wt%. DRUV–vis revealed that the substitution of N− and In3+ dopants on TiO2 lattice shifted the light absorption to the longer wavelength and reduced the band gap energy. The enhanced •OH radicals formation during the photocatalytic reaction was revealed by photoluminescence spectra. The photoluminescence spectra of synthesized catalysts revealed that the efficient charge separation of photo induced charge carriers for 0.3wt% N/In2O3–TiO2 nanocomposite. The enhanced surface area, large pore volume and large pore diameter for 0.3wt% N/In2O3–TiO2 improved the photocatalytic efficiency. In3+ ions can easily trap and transfer the excited electrons to the adsorbed O2 molecules, hence efficiently extending the life time of electron–hole pair.

Indium and cerium co-doped mesoporous TiO2 nanocomposites with enhanced visible light photocatalytic activity

Indium and cerium co-doped mesoporous TiO2 nanocomposites with different weight percentage were synthesized by sol–gel route using Pluronic P123 as the structure directing template. The synthesized materials were characterized by X-ray powder diffraction, high resolution transmission electron microscopy, scanning electron microscope with energy dispersive X-ray spectroscopy, N2 adsorption–desorption studies, X-ray photoelectron spectroscopy, diffuse reflectance UV–vis absorption spectroscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy and electron paramagnetic resonance spectroscopy. Indium and cerium co-doped on TiO2 nanocomposites shifted the light absorption band-edge position to visible region and showed high surface area with large pore diameter. The optimum loading of In2O3 and CeO2 on TiO2 was 0.2wt%. Ce4+ is good electron scavengers, which easily trapped the exited electrons and transferred the electrons to the adsorbed O2 molecules to produce O2−•. Hence the electron–hole recombination was efficiently suppressed, which was revealed by the photoluminescence spectroscopy. The large number of structural defects by the substitution of In3+ for Ti4+ enhanced the surface Brønsted acidity and the adsorption of cationic methylene blue. Consequently, In2O3/CeO2-TiO2 exhibited promising photocatalytic activity in the degradation of methylene blue under visible light irradiation due to the formation of large number of O2−• and •OH radicals.

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.

Preparation and Properties of Co-doped TiO$lt;inf$gt;2$lt;/inf$gt; with Assistance of Ionic Liquid

Co-doped mesoporous TiO2 photocatalysts were prepared by an ionic liquid 1-butyl-3-methylimida-zolium tetrafluoroborate ((C4MIM)BF4) modified Sol-Gel method. The effects of Co doping on the surface area, crystalline phase, chemical binding states and compositions, and absorbance of the Co-doped mesoporous TiO2 photocatalysts were studied by N2 adsorption-desorption measurements (BET), X-ray diffraction (XRD), X-ray photoelectron spec- troscopy (XPS), and UV-Vis diffuse reflectance absorption spectra (UV-Vis DRS). BET analysis showed that Co/TiO2 photocatalyst was mesoporous structure with large surface area. XRD patterns indicated that the Co-doped mesoporous TiO2 photocatalysts was anatase structure. XPS spectra indicated that the Co 2+ replaced Ti 4+ and entered into TiO2 lat- tice, which reduced the band gap of TiO2 and thereby extending the light response range to the visible region (UV-Vis spectra). Photocatalytic activity of the Co/TiO2 mesoporous photocatalysts was evaluated by photodegradation of me- thylene blue (MB) under visible light (λ>420 nm). Co-doped TiO2 exhibited obvious visible light activity for MB photodegradation, and 0.3%Co/TiO2 exhibited the highest photocatalytic activity.

Preparation, characterization and photocatalytic activity of lanthanum and vanadium co-doped mesoporous TiO2 for azo-dye degradation

Titanium dioxide photocatalysts co-doped with lanthanum and vanadium were prepared by a facile microwave-assisted hydrothermal method and characterized by XRD, SEM, N2 physisorption at 77K and DRS. The characterization showed that co-doped TiO2 samples have a high degree of crystallinity and existence of fully anatase phase. It was found that all the synthesized catalysts have the mesoporous structure. The co-doped TiO2 samples have larger BET surface areas and the mesopores volume than pure TiO2 and La doped samples. The vanadium co-doping contributes to the extension of absorption into the visible region. The photocatalytic activity of the samples was evaluated by the decolorization of textile dye Reactive Blue 52 in aqueous solutions under sun-like radiation. Compared with La singly doped TiO2, the co-doped catalysts showed an important improvement of photoactivity. The photocatalyst with 2% (w/w) La and 0.02% (w/w) V appeared to be the most photoactive. Optimal catalyst loading and the kinetics of degradation were also studied. Demonstrating higher photodegradation efficiency for RB than commercially available TiO2 Evonik P25, easy separation from suspension by spontaneous sedimentation and reusability of the catalyst, make this photocatalyst suitable for wastewater treatment.

Photocatalytic Activity of Fe and Ce Co‐doped Mesoporous TiO2 Catalyst under UV and Visible Light

AbstractThe catalysts of un‐doped, single‐doped and co‐doped mesoporous titanium dioxide (MTiO2) were prepared by a template method with tetrabutyltitanate (Ti(OC4H9)4) as a Ti source material and Pluronic P123 as a template. The photo‐absorbance of the obtained catalysts was measured by UV‐vis absorption spectroscopy, and the photocatalytic activities of the prepared samples under UV and visible light were estimated by measuring the degradation rate of methyl orange (MO) (50 mg/L) in an aqueous solution. 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 effect of Fe and Ce co‐dopants on the material properties was investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption‐desorption isotherm measurement. 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 photocatalytic activity of MTiO2 co‐doped with Fe and Ce was markedly improved due to the synergistic actions of the two dopants.

Photocatalytic activity of (sulfur, nitrogen)-codoped mesoporous TiO2 thin films

Nitrogen and sulfur co-doped mesoporous TiO2 thin films were fabricated using thiourea as a doping resource by the combination of the sol–gel and evaporation-induced self-assembly (EISA) processes. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, and UV–vis spectra were performed to characterize the as-synthesized mesoporous TiO2 materials. The XPS result shows that O–Ti–N and O–Ti–S bonds in the (S, N)-codoped mesoporous TiO2 were formed. The resultant mesoporous (S, N)-codoped TiO2 exhibited anatase framework with a high porosity and a narrow pore distribution. After being illuminated for 3 h, methyl orange (MO) could be degraded completely by the co-doped sample under the ultraviolet irradiation, whereas mesoporous TiO2 film without doping could only degrade 60% MO. After being illuminated by visible light, the water contact angles of the mesoporous co-doped TiO2 samples decreased slightly, but the pure TiO2 mesoporous film exhibited no change in the hydrophilicity.