Showing papers on "Photocatalysis published in 2007"
TL;DR: In this article, the up-to-date development of the above-mentioned technologies applied to TiO 2 photocatalytic hydrogen production is reviewed, based on the studies reported in the literature, metal ion-implantation and dye sensitization are very effective methods to extend the activating spectrum to the visible range.
Abstract: Nano-sized TiO 2 photocatalytic water-splitting technology has great potential for low-cost, environmentally friendly solar-hydrogen production to support the future hydrogen economy. Presently, the solar-to-hydrogen energy conversion efficiency is too low for the technology to be economically sound. The main barriers are the rapid recombination of photo-generated electron/hole pairs as well as backward reaction and the poor activation of TiO 2 by visible light. In response to these deficiencies, many investigators have been conducting research with an emphasis on effective remediation methods. Some investigators studied the effects of addition of sacrificial reagents and carbonate salts to prohibit rapid recombination of electron/hole pairs and backward reactions. Other research focused on the enhancement of photocatalysis by modification of TiO 2 by means of metal loading, metal ion doping, dye sensitization, composite semiconductor, anion doping and metal ion-implantation. This paper aims to review the up-to-date development of the above-mentioned technologies applied to TiO 2 photocatalytic hydrogen production. Based on the studies reported in the literature, metal ion-implantation and dye sensitization are very effective methods to extend the activating spectrum to the visible range. Therefore, they play an important role in the development of efficient photocatalytic hydrogen production.
3,714 citations
1,265 citations
TL;DR: In this article, Nitrogen-doped TiO2 nanocatalysts with a homogeneous anatase structure were successfully synthesized through a microemulsion−hydrothermal method by using some organic compounds such as triethylamine, urea, thiourea, and hydrazine hydrate.
Abstract: Nitrogen-doped TiO2 nanocatalysts with a homogeneous anatase structure were successfully synthesized through a microemulsion−hydrothermal method by using some organic compounds such as triethylamine, urea, thiourea, and hydrazine hydrate. Analysis by Raman and X-ray photoemission spectroscopy indicated that nitrogen was doped effectively and most nitrogen dopants might be present in the chemical environment of Ti−O−N and O−Ti−N. A shift of the absorption edge to a lower energy and a stronger absorption in the visible light region were observed. The results of photodegradation or the organic pollutant rhodamine B in the visible light irradiation (λ > 420 nm) suggested that the TiO2 photocatalysts after nitrogen doping were greatly improved compared with the undoped TiO2 photocatalysts and Degussa P-25; especially the nitrogen-doped TiO2 using triathylamine as the nitrogen source showed the highest photocatalytic activity, which also showed a higher efficiency for photodecomposition of 2,4-dichlorophenol. T...
961 citations
TL;DR: In this paper, a carbon-doped TiO2 photocatalyst was obtained by using glucose as a carbon source and was characterized by XRD, XPS, TEM, nitrogen adsorption, and UV-vis diffuse reflectance spectroscopy.
Abstract: A visible-light-active TiO2 photocatalyst was prepared through carbon doping by using glucose as carbon source. Different from the previous carbon-doped TiO2 prepared at high temperature, our preparation was performed by a hydrothermal method at temperature as low as 160 °C. The resulting photocatalyst was characterized by XRD, XPS, TEM, nitrogen adsorption, and UV–vis diffuse reflectance spectroscopy. The characterizations found that the photocatalyst possessed a homogeneous pore diameter about 8 nm and a high surface area of 126 m2/g. Comparing to undoped TiO2, the carbon-doped TiO2 showed obvious absorption in the 400–450 nm range with a red shift in the band gap transition. It was found that the resulting carbon-doped TiO2 exhibits significantly higher photocatalytic activity than the undoped counterpart and Degussa P25 on the degradation of rhodamine B (RhB) in water under visible light irradiation (λ > 420 nm). This method can be easily scaled up for industrial production of visible-light driven photocatalyst for pollutants removal because of its convenience and energy-saving.
898 citations
TL;DR: Polycrystalline BiFeO3 nanoparticles (size 80-120 nm) are prepared by a simple sol-gel technique as discussed by the authors, which are very efficient for photocatalytic decomposition of organic contaminants under irradiation from ultraviolet to visible frequencies.
Abstract: Polycrystalline BiFeO3 nanoparticles (size 80-120 nm) are prepared by a simple sol-gel technique. Such nanoparticles are very efficient for photocatalytic decomposition of organic contaminants under irradiation from ultraviolet to visible frequencies. The BiFeO3 nanoparticles also demonstrate weak ferromagnetism of about 0.06 mu(B)/Fe at room temperature, in good agreement with theoretical calculations.
819 citations
TL;DR: The percentage reduction of MO and R6G was estimated under UV/solar system and it was found that COD reduction takes place at a faster rate under solar light as compared to UV light.
780 citations
758 citations
668 citations
TL;DR: In this paper, the 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.
Abstract: Hierarchical 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, N 2 -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.
632 citations
TL;DR: In this article, the authors have focused on the mechanisms of the one-electron redox reactions of organic compounds during the TiO2 photocatalytic reactions and on the development of TiO 2-based materials.
Abstract: Titanium dioxide (TiO2) has been extensively investigated for the photocatalytic purification of air and water. In this article, we have focused on the mechanisms of the one-electron redox reactions of organic compounds during the TiO2 photocatalytic reactions and on the development of TiO2-based materials. It was clearly demonstrated that the adsorption dynamics of substrates and intermediates, the electronic interaction between TiO2 and adsorbates, and the band structure and morphology of TiO2 nanomaterials are crucial factors for establishing efficient photocatalytic reaction systems. The TiO2-based hybrid nanoparticles with various functional materials, such as polyoxometalates (POMs) and cyclodextrins (CDs), have been fabricated on the basis of the mechanistic aspects. New experimental methods, such as two-color two-laser flash photolysis and single-molecule fluorescence techniques, for the investigation of the TiO2 photocatalytic reactions have been demonstrated.
609 citations
TL;DR: In this article, the authors presented a systematic study on two different preparation methods for titanium dioxide with silver, and found that the latter produces a more effective photocatalytic material (6-50% improvement in catalytic efficiency), which is attributed to the fact that the silver is homogeneously dispersed throughout the material.
Abstract: This paper presents a systematic study on two different preparation methods for titanium dioxide with silver. The silver can be incorporated by irradiating the reaction mixture during preparation to reduce silver ion to silver metal or by direct calcination of the sol–gel material to decompose silver nitrate to silver. Of the two methods, we found the latter produces a more effective photocatalytic material (6–50% improvement in catalytic efficiency), which is attributed to the fact that the silver is homogeneously dispersed throughout the material. The efficiency of the materials were examined using a Q-Sun solar simulator (visible light) and in Dublin summer sunlight (latitude 54°N). In both cases, the addition of increasing amounts of silver, for both batches of samples, significantly increases the rate of degradation of a model dye, rhodamine 6G (R6G), increasing the rate of degradation from 0.06 min−1 for TiO2 to 0.34 min−1 for 5 mol% Ag–TiO2. This is attributed to the increasing visible absorption capacity due to the presence of silver nanoparticles.
TL;DR: A significant decrease in the COD values was observed, which clearly indicates that both photocatalytic and adsorption methods offer good potential to remove Rhodamine B from industrial effluents.
TL;DR: The photocatalytic activity of the as-prepared nanocrystalline mesoporous TiO2 powders was evaluated by the degradation of acetone (CH3COCH3) under UV-light irradiation at room temperature in air as mentioned in this paper.
Abstract: Bimodal nanocrystalline mesoporous TiO2 powders with high photocatalytic activity were prepared by a hydrothermal method using tetrabutylorthotitanate (TiO(C4H9)4, TBOT) as precursor. The as-prepared TiO2 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption measurements. The photocatalytic activity of the as-prepared TiO2 powders was evaluated by the photocatalytic degradation of acetone (CH3COCH3) under UV-light irradiation at room temperature in air. The effects of hydrothermal temperature and time on the microstructures and photocatalytic activity of the TiO2 powders were investigated and discussed. It was found that hydrothermal treatment enhanced the phase transformation of the TiO2 powders from amorphous to anatase and crystallization of anatase. All TiO2 powders after hydrothermal treatment showed bimodal pore-size distributions in the mesoporous region: one was intra-aggregated pores with maximum pore diameters of ca. 4–8 nm and the other with inter-aggregated pores with maximum pore diameters of ca. 45–50 nm. With increasing hydrothermal temperature and time, the average crystallite size and average pore size increased, in contrast, the Brunauer-Emmett-Teller (BET) specific surface areas, pore volumes and porosity steadily decreased. An optimal hydrothermal condition (180 °C for 10 h) was determined. The photocatalytic activity of the prepared TiO2 powders under optimal hydrothermal conditions was more than three times higher than that of Degussa P25.
TL;DR: In this paper, carbon and nitrogen co-doped TiO2 nanoparticles with different nitrogen and carbon contents were obtained by a sol−gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-Ray photoelectron spectroscopy (XPS), and UV−vis spectroscopic analysis.
Abstract: To utilize visible light more efficiently in photocatalytic reactions, carbon-doped TiO2 (C−TiO2), nitrogen-doped TiO2 (N−TiO2), and carbon and nitrogen co-doped TiO2 (C−N−TiO2) nanoparticles with different nitrogen and carbon contents were prepared by a sol−gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV−vis spectroscopy. XRD results showed that the doping of C and N atoms could suppress the crystal growth of TiO2, and the effect of C doping was more pronounced than that of N doping. XPS, UV−vis spectroscopy, and lattice parameter analysis revealed that N atoms could incorporate into the lattice of anatase through substituting the sites of oxygen atoms, while most C atoms could form a mixed layer of deposited active carbon and complex carbonate species at the surface of TiO2 nanoparticles. The photocatalytic activities of obtained C−TiO2, N−TiO2, and C−N−TiO2 samples with different C and N contents were evalua...
TL;DR: In this paper, the structure and properties of the co-doped particles were studied by XRD, XPS, Raman, FL, and UV-diffuse reflectance spectra.
Abstract: Nanoparticles of titanium dioxide co-doped with nitrogen and iron (III) were first prepared using the homogeneous precipitation-hydrothermal method. The structure and properties of the co-doped were studied by XRD, XPS, Raman, FL, and UV-diffuse reflectance spectra. By analyzing the structures and photocatalytic activities of the undoped and nitrogen and/or Fe3+-doped TiO2 under ultraviolet and visible light irradiation, the probable mechanism of co-doped particles was investigated. It is presumed that the nitrogen and Fe3+ ion doping induced the formation of new states closed to the valence band and conduction band, respectively. The co-operation of the nitrogen and Fe3+ ion leads to the much narrowing of the band gap and greatly improves the photocatalytic activity in the visible light region. Meanwhile, the co-doping can also promote the separation of the photogenerated electrons and holes to accelerate the transmission of photocurrent carrier. The photocatalyst co-doped with nitrogen and 0.5% Fe3+ sho...
TL;DR: In this article, the authors reviewed the development in the highly dispersed titanium oxide photocatalysts prepared on or within zeolites and the visible light-responsive TiO 2 catalysts.
Abstract: Recent development in titanium oxide-based photocatalysts was reviewed concerning the development in the highly dispersed titanium oxide photocatalysts prepared on or within zeolites and the visible light-responsive TiO 2 photocatalysts. The unique and high reactivities of titanium oxide species anchored or incorporated in the zeolite for various photocatalytic reactions such as reduction of CO 2 with H 2 O and direct decomposition of NO x into N 2 and O 2 were discussed focusing on the relationship between the reactivity and local structures of the catalysts. Moreover, the preparation of the visible light-responsive TiO 2 photocatalysts by applying ion-engineering techniques such as an ion-implantation and an RF magnetron sputtering deposition method was discussed focusing on its unique reactivity for the decomposition of water into H 2 and O 2 with a separate evolution under sunlight irradiation.
TL;DR: The systematic approach presented in this study demonstrates that a substantial improvement of the photocatalytic activity of TiO2 can be achieved by a careful design of the particle morphology and the control of the surface chemistry.
Abstract: The possibility of controlling the photocatalytic activity of TiO2 nanoparticles by tailoring their crystalline structure and morphology is a current topic of great interest. In this study, a broad variety of well-faceted particles with different phase compositions, sizes, and shapes have been obtained from concentrated TiOCl2 solutions by systematically changing temperature, pH, and duration of the hydrothermal treatment. The guide to select the suitable experimental conditions was provided by thermodynamic modeling based on available thermochemical data. By combining the results of TEM, HRTEM, XRD, density, and specific surface area measurements, a complete structural and morphological characterization of the particles was performed. Correlation between the photocatalytic activity in the UV photodegradation of phenol solutions and the particle size was established. Prismatic rutile particles with length/width ratio around 5 and breadth of 60−100 nm showed the highest activity. The surface chemistry of t...
TL;DR: It is found that under the influence of TiO2 as catalyst the colored solution of the dye Safranin-T becomes colorless and the process follows first-order reaction kinetics, which implies that the photodegradation throughTiO2 is a safer technique.
TL;DR: In this article, the formation of one-dimensional CdS nanowires was investigated by a solvothermal method in ethylenediamine as a single solvent at different temperatures and times.
Abstract: To investigate the formation of one-dimensional CdS nanowires, we synthesized them by a solvothermal method in ethylenediamine as a single solvent at different temperatures and times. The sample synthesized at 160 °C for 72 h had an average diameter of ca. 50 nm and a length of ca. 3−4 μm and hexagonal phase with high crystallinity. It was revealed that the formation of CdS nanowires followed three-step processes during the solvothermal synthesis; the seed formation process yielded nanosheets emanating from a mirosphere followed by the nanorod formation and growth of nanorods to nanowires. The CdS nanowires with higher crystallinity showed a higher rate of photocatalytic hydrogen production from water containing 0.1 M Na2S and 0.0 2M Na2SO3 as sacrificial reagents under visible light irradiation (λ ≥ 420 nm). A high and stable photocurrent generation was also observed from the CdS nanowire film under visible light.
TL;DR: In this paper, the formation mechanism and effect of reaction time on the products were investigated and the photocatalytic property demonstrated that the as-synthesized Bi2WO6 structures showed excellent photocatalysis activity exposure to visible light irradiation.
Abstract: Bismuth tungstate hierarchical nest-like structures built by higher order nanoplate alignment have been successfully synthesized by a facile and economical method in the presence of polyvinyl pyrrolidone. The formation mechanism and effect of reaction time on the products were investigated. In addition, studies of the photocatalytic property demonstrate that the as-synthesized Bi2WO6 structures show excellent photocatalytic activity exposure to visible light irradiation. Furthermore, we first explored the electrochemical property of the Bi2WO6 nanostructure as an electrode in a lithium ion battery. Therefore, the preparation and properties studies of Bi2WO6 structures suggest potential future applications in photocatalysis by sunlight and as an electrode candidate in lithium ion batteries.
TL;DR: A dye-sensitized CuO incorporated TiO 2 catalyst was found to be an active photocatalyst for the photocatalytic hydrogen production from water under visible light (> 420nm) irradiation in the presence of electron donors such as triethanolamine, acetonitrile and triethylamine as mentioned in this paper.
TL;DR: Results demonstrate that UVA-TiO(2) photocatalysis can be a very effective approach for degrading sulfonamide micropollutants, particularly in natural waters exhibiting either alkaline pH or low concentrations of NOM, or both conditions.
TL;DR: In this article, a multi-walled carbon nanotube (MWCNT) supported TiO2 composite catalysts were prepared by sol-gel and hydrothermal methods.
TL;DR: In this paper, the average crystallite size of prepared ZnO nanopowder was determined from XRD pattern using Debeye-Scherrer equation in the range of 14nm.
TL;DR: The results indicated preparation method was the decisive factor rather than size and morphology in the final degradation efficiency of ZnO powders.
TL;DR: In this article, X-ray diffraction, transmission electron microscopy and Xray photoelectron spectroscopy were used to characterize as-prepared composites of titanium dioxide (anatase, TiO 2 ) nanoparticles.
TL;DR: In this paper, a milling-annealing method was used for the preparation of Bi2O3/BaTiO3, which exhibited better photocatalytic properties than the single-phase BaTiOO3 or Bi 2O3 and was attributed mainly to the electric field driven electron−hole separations both at the interface and in the semiconductors.
Abstract: The heterojunction semiconductors Bi2O3/BaTiO3 were prepared by a milling-annealing method. The powders were characterized by X-ray diffraction (XRD), the Brunauer−Emmett−Teller (BET) method, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and UV−vis diffuse reflection spectroscopy (DRS). Their UV-induced photocatalytic activities were evaluated by the degradations of methyl orange and methylene blue. The results generally show that the heterojunction semiconductors Bi2O3/BaTiO3 exhibit better photocatalytic properties than the single-phase BaTiO3 or Bi2O3. The obviously increased performance of Bi2O3/BaTiO3 is ascribed mainly to the electric-field-driven electron−hole separations both at the interface and in the semiconductors. A strategy for the design of efficient heterojunction photocatalysts was proposed. That is, an electron-accepting semiconductor and a hole-accepting semiconductor with matching band potentials, which respectively possess high electron and hole c...
TL;DR: In this article, pure rutile nanorods were synthesized by hydrolysis of TiCl4 ethanolic solution in water at 50 °C and the resulting samples were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscope, high-resolution transmission electron microscope, nitrogen sorption, and UV−vis diffuse reflectance spectrum.
Abstract: Pure rutile nanorods were synthesized by hydrolysis of TiCl4 ethanolic solution in water at 50 °C. The assembly of rutile nanorods could be controlled through simply changing the molar ratios of TiCl4, ethanol, and water, resulting in different superstructures with flower- or urchinlike morphologies. The resulting samples were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, nitrogen sorption, and UV−vis diffuse reflectance spectrum. A possible mechanism for the growth and assembly of rutile nanorod superstructures was proposed on the basis of characterization results. More importantly, we found that those low temperature synthesized superstructures showed significantly higher photocatalytic activities than commercial photocatalyst P25 on degradation of rhodamine B in water under artificial solar light. This study provides a simple and inexpensive way to prepare high active rutile nanorods superstructure...
TL;DR: A transmission electron microscopy image illustrated that catalyst nanoparticles adhere to the outer membrane of the cell and act as an inhibitor to the nourishment of bacteria from aqueous media.
Abstract: Apatite-coated Ag/AgBr/TiO2 was prepared by deposition of Ag as novel metal to generate electron−hole pairs by extending the excitation wavelength to the visible-light region, AgBr, and hydroxy apatite as photosensitive material and adsorption bioceramic, respectively. The energy dispersive X-ray spectrometry clearly showed the presence of Ti, Ag, Ca, and P elements on the surface of catalyst. The bactericidal experiments in dark media indicated that only the novel catalyst shows inhibiting growth of bacteria in this case. A transmission electron microscopy image illustrated that catalyst nanoparticles adhere to the outer membrane of the cell and act as an inhibitor to the nourishment of bacteria from aqueous media. The novel catalyst also showed higher photocatalytic activity compared to Ag/AgBr/TiO2 photocatalyst under visible-light irradiation. The inactivation of E. coli is due to the ability of the catalyst to adhere to the outer cell in addition to destruction of the cell wall by various reactive sp...