Mesoporous Titania Photocatalysts Research Articles

Preparation, Characterization, Photocatalytic Activity of S and Ag co-Doped Mesoporous Titania Photocatalysts

In order to improve the photocatalytic performance of mesoporous titania under visible light, a series of photocatalysts of S and Ag co-doped mesoporous titania have been successfully prepared by template method using thiourea, AgNO3 and tetrabutyl titanate as precursors and Pluronic P123 (EO20PO70EO20) as template. Scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption measurements, and UV-visible spectroscopy were employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The microcrystal of the photocatalysts consisted of anatase phase and was approximately present in the form of spherical particle. The photocatalytic performance was studied by photodegradation methyl orange in water under UV and visible light irradiation. The calcination temperature and the doping content influenced the photoactivity. In addition, the possibility of cyclic usage of co-doped mesoporous titania was also confirmed, the photocatalytic activity of mesoporous titania remained above 89% of the fresh sample after being used four times. It was shown that the co-doped mesoporous titania could be activated by visible light and could thus be potentially applied for the treatment of water contaminated by organic pollutants. The synergistic effect of sulfur and silver co-doping played an important role in improving the photocatalytic activity.

Understanding the role of cyclodextrins in the self-assembly, crystallinity, and porosity of titania nanostructures.

A series of mesoporous titania photocatalysts with tailorable structural and textural characteristics was prepared in aqueous phase via a colloidal self-assembly approach using various cyclodextrins (CDs) as structure-directing agents. The photocatalysts and the structure-directing agents were characterized at different stages of the synthesis by combining X-ray diffraction, N2-adsorption, field emission scanning electron microscopy, transmission electron microscopy, UV-visible spectroscopy, dynamic light scattering, and surface tension measurements. The results demonstrate that the cyclic macromolecules efficiently direct the self-assembly of titania colloids, resulting in a fine-tuning of the crystal phase composition, crystallite size, surface area, particle morphology, pore volume, and pore size. Depending on the chemical nature of the substituents in the cyclodextrin ring, synergistic or competitive effects arising from the adsorption capacity of these cyclic oligosaccharides onto titania surface, surface-active properties, and ability to aggregate in water by intermolecular interactions were found to substantially impact the characteristics of the final material. We propose that, in contrast to the native cyclodextrins, which tend to favor the local agglomeration of titania nanoparticles due to the strong intermolecular interactions, the substitution of hydroxyl groups by a relatively large number of methoxyl or 2-hydropropoxyl ones in the β-CD derivatives allows for creating smoother interfaces, thus facilitating the self-assembly of the colloids in a more homogeneous network. The photocatalytic activity of those titania materials was evaluated in the photodegradation of a toxic herbicide, phenoxyacetic acid, and was correlated to the structural and textural characteristics of the photocatalysts.

Preparation and photocatalytic activity of visible-light-driven mesoporous titania photocatalyst co-doped with B and S

Preparation and photocatalytic activity of visible-light-driven mesoporous titania photocatalyst co-doped with B and S

Visible-Light Degradation of Dyes and Phenols over Mesoporous Titania Prepared by Using Anthocyanin from Red Radish as Template

Heterogeneous photocatalysis is able to operate effectively to eliminate organic compounds from wastewater in the presence of semiconductor photocatalyst and a light source. Although photosensitization of titania by organic dyes is one of the conventional ways for visible-light utilization of titania, previous studies have not yet addressed the use of natural food coloring agents as templates in the synthesis of mesostructured materials, let alone the simultaneous achievement of highly crystalline mesoscopic framework and visible-light photocatalytic activity. In this work, anthocyanin, a natural pigment from red radish was directly used as template in synthesis of highly crystalline mesoporous titania. The synthesized mesoporous titania samples were characterized by a combination of various physicochemical techniques, such as XRD, SEM, HRTEM, nitrogen adsorption/desorption, and diffuse reflectance UV-Vis. The prepared mesoporous titania photocatalyst exhibited significant activity under visible-light irradiation for the degradation of dyes and phenols due to its red shift of band-gap-absorption onset and visible-light response as a result of the incorporation of surface carbon species.

Co-doped mesoporous titania photocatalysts prepared from a peroxo-titanium complex solution

In this study, nitrogen doped and nitrogen/silver co-doped TiO2 photocatalsysts were fabricated using a sol–gel method at room temperature. The obtained gels were neutralized, washed with pure water, and calcined at 400°C for 4h. The photocatalysts were characterized by scanning and transmission electron microscopy, X-ray diffraction, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and BET specific surface area. The results showed that spherical particles with anatase structure were produced after annealing at 400°C.N 1s (400eV) and Ag 3d (367.3eV) states indicated that nitrogen doping and silver co-doping were in the form of NO bonds and AgO, respectively. The photocatalytic activity of photocatalysts was investigated using a batch reactor system exposed to artificial solar irradiation. Both nitrogen and silver/nitrogen co-doped materials were effective in the photocatalytic degradation of hexamethyl pararosaniline chloride.

Preparation and characterization of sulfur-modified mesoporous titania photocatalyst

Sulfur-modified mesoporous titania (S-MTiO2) was investigated as a potential photocatalyst under visible light. The photocatalyst was prepared by template method using thiourea and tetrabutyl titanate (Ti(OC4H9)4) as precursors and Pluronic P123 as template. The photoabsorbance of as-prepared photocatalyst was measured by UV-vis absorption spectroscopy, which confirmed the extension of absorption into the visible region. The microstructure of S-MTiO2 was characterized using X-ray diffraction (XRD) and N2 adsorption-desorption measurements. The micro crystal of the S-doped photocatalyst consisted of anatase phase and no significant influence on the nature of crystal formation. X-ray photoelectron spectroscopy (XPS) measurements indicated the presence of C in the prepared photocatalyst in addition to S. The photo-catalytic performance was studied by photodegradation methyl orange (MO) in water under visible light irradiation. The calcination temperature and the doping content influenced the photoactivity.

Soft-chemical synthesis of mesoporous nitrogen-modified titania with superior photocatalytic performance under visible light irradiation

Exploring novel titania-based semiconductor photocatalysts with both high specific surface area and expanded visible light response is still a challenge. In this work, we report the first synthesis of mesoporous nitrogen-modified titania by a facile and convenient exfoliation–reassembling strategy. Ethylamine is used for the delamination of layered titanate, and meanwhile, also serves as a source of nitrogen. X-ray diffraction patterns and transmission electron microscopy images reveal that the random reassembling between titanate nanosheets and anatase nanoparticles give rise to its porous structure. N2 adsorption–desorption isotherms demonstrate that the obtained photocatalyst is fairly high in specific surface area and in mesoporosity (SBET of ∼215m2g−1 and pore size of ∼5.6nm) for effective photocatalysis. The mesoporous titania photocatalyst possesses an extended absorption in the visible region due to the successful modification by NHx species, which is confirmed using the X-ray photoelectron spectroscopic analysis, combined with the Fourier-transform infrared spectra. Photocatalytic tests reveal that the mesoporous nitrogen-modified titania material show an excellent catalytic performance for the degradation of organic compounds under visible light irradiation, which is much higher than those of the commercial P25, pristine protonic titanate, and N-doped mesoporous titania photocatalyst prepared from a template-free route. The present work provides a new way to develop efficient nitrogen-modified oxides materials with high specific surface area and enhanced visible light absorption for solar energy utilization.

Mesoporous titania photocatalyst: effect of relative humidity and aging on the preparation of mesoporous titania and on its photocatalytic activity performance

Mesoporous TiO2 has been synthesized by the sol–gel method, using a nonionic triblock copolymer P123 as surfactant template under acidic conditions. The as-prepared samples were characterized by thermogravimetry–differential thermal analysis (TG–DTA), nitrogen absorption–desorption (BET), field emission scanning electron microscopy, and transmission electron microscopy. The photocatalytic activity of the mesoporous TiO2 was evaluated by degradation of methylene blue under high-intensity UV light irradiation; the amount of methylene blue was measured by UV–visible spectroscopy. TG–DTA analysis revealed that the surfactant had been removed partly in as-synthesized samples. BET analysis proved that all the samples retained mesoporosity with a narrow pore-size distribution (4.5–6.3 nm) and high surface area (103–200 m2/g). All calcined mesoporous TiO2 had high photocatalytic activity in the photodegradation of methylene blue.

Preparation and characterization of visible-light-driven europium doped mesoporous titania photocatalyst

Pure and different content europium (Eu) doped mesoporous titania were prepared by template method using Eu(NO 3) 3·6H 2O and Ti(OC 4H 9) 4 as precursors and Pluronic P123 as template and characterized with X-ray diffraction (XRD), N 2 adsorption-desorption measurements, and ultraviolet-visible diffuse absorption spectra. Their photocatalytic activities were studied by photodegradation phenol in water under visible light irradiation. The results showed that Eu doping restrained the growth of grain size and extended the photoabsorption edge of mesoporous titania into the visible light region, which made Eu-doped mesoporous titania possess high photocatalytic activity under visible light. In the experiment condition, the photocatalytic activity of 0.2 mol.% Eu doped mesoporous titania was optimal of all the prepared samples.

Mesoporous titania photocatalysts: preparation, characterization and reaction mechanisms

Titanium dioxide is a very important semiconductor with a high potential for applications in photocatalysis, solar cells, photochromism, sensoring, and various other areas of nanotechnology. Increasing attention has recently been focused on the simultaneous achievement of high bulk crystallinity and the formation of ordered mesoporous TiO2 frameworks with high thermal stability. Mesoporous TiO2 has continued to be highly active in photocatalytic applications because it is beneficial for promoting the diffusion of reactants and products, as well as for enhancing the photocatalytic activity by facilitating access to the reactive sites on the surface of photocatalyst. This steady progress has demonstrated that mesoporous TiO2 nanoparticles are playing and will continue to play an important role in the protection of the environment and in the search for renewable and clean energy technologies. This review focuses on the preparation and characterisation of mesoporous titania, noble metals nanoparticles, transition metal ions, non-metal/doped mesoporous titania networks. The photocatalytic activity of mesoporous titania materials upon visible and UV illumination will be reviewed, summarized and discussed, in particular, concerning the influence of preparation and solid-state properties of the materials. Reaction mechanisms that are being discussed to explain these effects will be presented and critically evaluated.

Preparation of mesoporous titania particles using ionic liquid dissolving starch as templates

A mesoporous titania photocatalyst was prepared via calcining the solution of ionic liquid (1-methyl-3-butyl imidazolium bromide, [BMIM]Br) containing tetrabutyl titanate (TBT) and starch. The microstructure of the prepared mesoporous titania was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption/desorption isotherm. The results indicate that the resulting mesoporous titania has a grain size of about 13.9 nm, a special surface area of 106 m2/g, and a pore volume of 0.22 cm3/g, and the pore size can be adjusted by the concentration of starch in ionic liquid. The photocatalytic activity of mesoporous titania in the degradation of methyl orange solution was determined. The effect of the specific surface area of mesoporous titania on the photocatalytic activity was also studied. The prepared mesoporous titania exhibits a high catalytic activity.

Preparation and characterization of nano silver-doped mesoporous titania photocatalysts for dye degradation

Photodegradation of Methyl orange is done over TiO 2 and nano silver-doped TiO 2. Sol–gel method of preparation is used to get improved structural properties as well as photocatalytic activity for environmental pollutant degradation. Glucose takes the role of the reductant for nano silver preparation together with urea as a stabilizer of nanoparticles. Both of these are working as templates and lead to mesoporous TiO 2 formation . Ag doping is found to be very effective in increasing the photoactivity of TiO 2 in dye degradation. Present work introduces a new route for nano Ag-doped mesoporous TiO 2 preparation which eliminates the presence of sodium which is a catalytic poison. Efficient dispersion of the inserted metal within the TiO 2 matrix is proved from various characterization techniques such as XRD (X-ray Diffraction), TEM (Transmission Electron Microscope), etc.

UV and solar light degradation of dyes over mesoporous crystalline titanium dioxides prepared by using commercial synthetic dyes as templates

Although photosensitization of titania by organic dyes is one of the conventional ways for visible-light utilization of titania, previous studies have not yet addressed the use of dyes as templates in the synthesis of mesoporous materials, let alone the simultaneous achievement of highly crystalline mesoscopic ordering and visible-light photocatalytic activity. In this work, fourteen commercial synthetic dyes were directly used as structure-directing agents which convert to carbonaceous materials after 400 °C calcination in synthesis of thermally stable mesostructured titania. This in situ carbon enhanced the visible light photocatalytic activities for the degradation of aqueous dyes. The synthesized mesoporous titania samples were characterized by a combination of various physicochemical techniques, such as XRD, SEM, HRTEM, nitrogen adsorption/desorption, TGA–DSC, XPS, diffuse reflectance UV–vis and FT–IR. Most of prepared mesoporous titania photocatalysts exhibited better activity under outside solar light than under artificial UV light, due to the presence of carbonaceous species which were transferred from the dye templates. The reported strategies combine sol-gel chemistry and self-assembly routes directly using dye templates that tune the material's architecture, texture and particularly function, visible-light photocatalysis.

3‐D Molecular Assembly of Function in Titania‐Based Composite Material Systems

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3-D Molecular Assembly of Function in Titania-Based Composite Material Systems

Various examples of composite titania-based nanostructured materials exhibiting cooperative functionalities between different active components are presented. The fabrication of these integrated composite materials is based on one-pot supramolecular templating techniques combined with acidic sol-gel chemistry. The defined 3-D nanoscale organization and integration of various functional components results in advanced optoelectronic and photonic applications such as visible light sensitization of mesoporous titania photocatalysts with cadmium sulfide nanocrystals acting as sensitizing integral part of the mesopore wall structure, narrow bandwidth emission from rare earth ion activated nanocrystalline mesoporous titania films, and mirrorless lasing in dye-doped hybrid organic/inorganic mesostructured titania waveguides.