Showing papers on "Photocatalysis published in 2006"
TL;DR: An advance in the catalysis of the overall splitting of water under visible light is described: the new catalyst is a solid solution of gallium and zinc nitrogen oxide, modified with nanoparticles of a mixed oxide of rhodium and chromium, which functions as a promising and efficient photocatalyst in promoting the evolution of hydrogen gas.
Abstract: Enhancing catalytic performance holds promise for hydrogen production by water splitting in sunlight.
2,537 citations
TL;DR: Co3O4/BiVO4 composite photocatalyst with a p-n heterojunction semiconductor structure has been synthesized by the impregnation method and exhibits enhanced photocatalytic activity for phenol degradation under visible light irradiation.
Abstract: Co3O4/BiVO4 composite photocatalyst with a p−n heterojunction semiconductor structure has been synthesized by the impregnation method. The physical and photophysical properties of the composite photocatalyst have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transimission electron microscopy (TEM), BET surface area, and UV−visible diffuse reflectance spectra. Co is present as p-type Co3O4 and disperses on the surface of n-type BiVO4 to constitute a heterojunction composite. The photocatalyst exhibits enhanced photocatalytic activity for phenol degradation under visible light irradiation. The highest efficiency is observed when calcined at 300 °C with 0.8 wt % cobalt content. On the basis of the calculated energy band positions and PL spectra, the mechanism of enhanced photocatalytic activity has been discussed.
820 citations
TL;DR: These results provide a characterization of the electronic states associated with N impurities in TiO2 and, for the first time, a picture of the processes occurring in the solid under irradiation with visible light.
Abstract: Nitrogen-doped titanium dioxide (N-TiO2), a photocatalytic material active in visible light, has been investigated by a combined experimental and theoretical approach. The material contains single-atom nitrogen impurities that form either diamagnetic (Nb-) or paramagnetic (Nb•) bulk centers. Both types of Nb centers give rise to localized states in the band gap of the oxide. The relative abundance of these species depends on the oxidation state of the solid, as, upon reduction, electron transfer from Ti3+ ions to Nb• results in the formation of Ti4+ and Nb-. EPR spectra measured under irradiation show that Nb centers are responsible for visible light absorption with promotion of electrons from the band gap localized states to the conduction band or to surface-adsorbed electron scavengers. These results provide a characterization of the electronic states associated with N impurities in TiO2 and, for the first time, a picture of the processes occurring in the solid under irradiation with visible light.
820 citations
TL;DR: In this paper, high-crystalline monoclinic scheelite BiVO4 powders are synthesized from aqueous Bi(NO3)3 and NH4VO3 solutions over a wide range of pH by a hydrothermal process.
Abstract: Highly crystalline monoclinic scheelite BiVO4 powders are synthesized from aqueous Bi(NO3)3 and NH4VO3 solutions over a wide range of pH by a hydrothermal process BiVO4 powders with various morphologies, surface textures, and grain shapes are selectively synthesized by adjusting the pH The dependence of the Raman peak position and intensity on the synthesis conditions indicates that the symmetry distortions in the local structure of the synthesized BiVO4 are affected by the preparation conditions These variations in the local structure result in the modification of the electronic structure of BiVO4, which results in a blue-shift in the UV-vis absorption spectrum of hydrothermally synthesized BiVO4 in comparison with a well-crystallized sample prepared by homogeneous coprecipitation The photocatalytic activities for O2 evolution from an aqueous AgNO3 solution under visible-light irradiation are strongly dependent on the pH used in the synthesis The differences in the photocatalytic activities between BiVO4 samples prepared under various conditions is attributed to the degree of structural distortion, leading to differences in the mobility of photogenerated holes formed in the valence band, which consists of Bi 6s and O 2p orbitals
810 citations
TL;DR: A rate equation for the degradation based on Langmuir-Hinshelwood (L-H) model has been proposed and results show that the adsorption constant and rate constant in L-H model are dependent to the light intensity, and increase with increasing the lightintensity.
784 citations
TL;DR: The morphology of the alpha-Fe2O3 was strongly influenced by the silicon doping, decreasing the feature size of the mesoscopic film, and the best performing photoanode would yield a solar-to-chemical conversion efficiency of 2.1% in a tandem device using two dye-sensitized solar cells in series.
Abstract: Thin, silicon-doped nanocrystalline α-Fe2O3 films have been deposited on F-doped SnO2 substrates by ultrasonic spray pyrolysis and chemical vapor deposition at atmospheric pressure. The photocatalytic activity of these films with regard to photoelectrochemical water oxidation was measured at pH 13.6 under simulated AM 1.5 global sunlight. The photoanodes prepared by USP and APCVD gave 1.17 and 1.45 mA/cm2, respectively, at 1.23 V vs RHE. The morphology of the α-Fe2O3 was strongly influenced by the silicon doping, decreasing the feature size of the mesoscopic film. The silicon-doped α-Fe2O3 nano-leaflets show a preferred orientation with the (001) basal plane normal to the substrate. The best performing photoanode would yield a solar-to-chemical conversion efficiency of 2.1% in a tandem device using two dye-sensitized solar cells in series.
754 citations
TL;DR: The results indicate that AgBr is the main photoactive species for the destruction of azodyes and bacteria under visible light.
Abstract: Ag/AgBr/TiO2 was prepared by the deposition-precipitation method and was found to be a novel visible light driven photocatalyst. The catalyst showed high efficiency for the degradation of nonbiodegradable azodyes and the killing of Escherichia coli under visible light irradiation (lambda>420 nm). The catalyst activity was maintained effectively after successive cyclic experiments under UV or visible light irradiation without the destruction of AgBr. On the basis of the characterization of X-ray diffraction, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, the surface Ag species mainly exist as Ag0 in the structure of all samples before and after reaction, and Ag0 species scavenged hVB+ and then trapped eCB- in the process of photocatalytic reaction, inhibiting the decomposition of AgBr. The studies of ESR and H2O2 formation revealed that *OH and O2*- were formed in visible light irradiated aqueous Ag/AgBr/TiO2 suspension, while there was no reactive oxygen species in the visible light irradiated Ag0/TiO2 system. The results indicate that AgBr is the main photoactive species for the destruction of azodyes and bacteria under visible light. In addition, the bactericidal efficiency and killing mechanism of Ag/AgBr/TiO2 under visible light irradiation are illustrated and discussed.
559 citations
558 citations
TL;DR: In this article, the effect of sulphuric and nitric acid on the photocatalytic properties of copper-doped TiO 2 was investigated and a comparison with undoped system was also made.
Abstract: Photocatalytic oxidation of phenol was performed over copper doped TiO 2 prepared by a sol–gel method. Different preparation methods were followed and a comparison with undoped system was also made. Wide structural and surface characterization of catalysts was carried out in order to establish a correlation between the effect of sulphuric and nitric acids present in the initial solution and the Cu–TiO 2 photocatalytic properties. The presence of sulphuric acid clearly stabilizes Cu–TiO 2 and TiO 2 structure and surface against sintering, maintaining anatase phase and relatively high surface area values with respect non sulphated Cu–TiO 2 or TiO 2 . Best photocatalytic behaviour is found for sulphated TiO 2 , as previously reported. In addition, incorporation of copper ions into the structure seems to enhance the photoactivity of the system for acidified systems, being the sulphated one the most favourable photocatalyst. The optimum metal loading is found for 0.5 M% of copper ion. A possible explanation of this photocatalytic improvement might be related to the stabilization of Cu 2 O species in doped TiO 2 prepared in the presence of sulphuric acid. This stabilization could be related to the presence of oxygen vacancies generated in the preparation procedure using sulphuric acid.
498 citations
TL;DR: In this paper, high surface area Ag-ZnO catalysts have been made by flame spray pyrolysis (FSP) and characterized by X-ray diffraction (XRD), nitrogen adsorption, UV-vis spectroscopy and electron microscopy (SEM) combined with TEM for elemental mapping.
Abstract: High surface area Ag-ZnO catalysts have been made by flame spray pyrolysis (FSP) and characterized by X-ray diffraction (XRD), nitrogen adsorption, UV–vis spectroscopy and electron microscopy (SEM and transmission electron microscopy (TEM)) combined with energy dispersive X-ray spectroscopy (EDXS) for elemental mapping. Silver metal clusters deposited directly on ZnO nanocrystals were obtained from this process. The Ag loading (1–5 at.%) controlled the Ag cluster size from 5 to 25 nm but did not influence the ZnO crystal size. Photodegradation of 10 ppm methylene blue (MB) solution was used to evaluate the performance of these FSP-made Ag-ZnO and was compared to wet-made Ag-ZnO and reference titania photocatalysts. The rate of photodegradation was optimal for Ag loading around 3 at.%. The best photocatalytic performance was exhibited by flame-made Ag-ZnO produced at the longest high-temperature residence times having high crystallinity as determined by XRD and UV–vis.
481 citations
TL;DR: In this paper, the authors describe the application of novel chemistry methods for the fabrication of robust nanostructured titanium oxide (TiO2) photocatalysts, which can be applied in the development of efficient photocATalytic systems for the treatment of water.
Abstract: This study describes the application of novel chemistry methods for the fabrication of robust nanostructured titanium oxide (TiO2) photocatalysts. Such materials can be applied in the development of efficient photocatalytic systems for the treatment of water. Mesoporous photocatalytic TiO2 films and membranes were synthesized via a simple synthesis method that involves dip-coating of appropriate substrates into an organic/inorganic sol composed of isopropanol, acetic acid, titanium tetraisopropoxide, and polyoxyethylenesorbitan monooleate surfactant (Tween 80) followed by calcination of the coating at 500 8C. Controlled hydrolysis and condensation reactions were achieved through in-taking of water molecules released from the esterification reaction of acetic acid with isopropanol. The subsequent stable incorporation of Ti–O–Ti network onto self-assembled surfactants resulted in TiO2 photocatalysts with enhanced structural and catalytic properties. The properties included high surface area (147 m 2 /g) and porosity (46%), narrow pore size distribution ranging from 2 to 8 nm, homogeneity without cracks and pinholes, active anatase crystal phase, and small crystallite size (9 nm). These TiO2 photocatalysts were highly efficient for the destruction of methylene blue and creatinine in water. High water permeability and sharp polyethylene glycol retention of the prepared photocatalytic TiO2/Al2O3 composite membranes evidenced the good structural properties of TiO2 films. In addition, the multi-coating procedure made it possible to effectively control the physical properties of TiO2 layer such as the coating thickness, amount of TiO2, photocatalytic activity, water permeability and organic retention. # 2005 Elsevier B.V. All rights reserved.
TL;DR: In this paper, the photocatalytic degradation of two Direct diazo dyes, Direct red 23 (DR 23) and Direct blue 53 (DB 53), was investigated under UV-A light irradiation.
Abstract: Silver nanoparticles doped TiO2 has been prepared and characterised by surface analytical methods such as BET surface area, scanning electron micrographs (SEM), X-ray diffraction (XRD), energy dispersive X-ray micro analysis (EDX), electron spin resonance (ESR) and diffuse reflectance spectroscopy (DRS). We have investigated the photocatalytic degradation of two Direct diazo dyes, Direct red 23 (DR 23) and Direct blue 53 (DB 53) in the aqueous suspensions of TiO2 and Ag deposited TiO2 nanoparticles under UV-A light irradiation in order to evaluate the various effects of silver deposition on the photocatalytic activity of TiO2. The presence of silver in TiO2 was found to enhance the photodegradation of DR 23 and DB 53. The higher activity of silver doped TiO2 is due to the enhancement of electron–hole separation by the electron trapping of silver particles.
TL;DR: In this article, the photocatalytic activity of Fe 3+ -doped anatase nanosized TiO 2 photocatalyst was investigated for the degradation of active yellow XRG dye.
Abstract: Fe 3+ -doped anatase nanosized TiO 2 photocatalysts have been prepared by combining sol–gel method with hydrothermal treatment. The samples were characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET)-specific surface area ( S BET ), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectroscopy and X-ray photoelectron spectroscopy (XPS). From results of UV–vis diffuse reflectance spectroscopy, Fe 3+ -doped TiO 2 extends its absorption to longer than 500 nm, which leads to an obvious photocatalatic activity under visible irradiation. From XRD, EPR, AAS and XPS, it was found that Fe exist in trivalent ionic state substituting Ti 4+ in TiO 2 lattice and its concentration decreases from the surface to the center of doped TiO 2 . The photocatalytic activity of prepared samples was investigated for the photocatalytic degradation of active yellow XRG dye. The photocatalytic activity of TiO 2 doped with appropriate content of Fe 3+ exceeded those of non-doped TiO 2 and P25 both under UV and visible light irradiation.
TL;DR: The TiO2/AC was shown high photoactivity for the photodegradation of methyl orange (MO) dyestuff in aqueous solution under UV irradiation and the kinetics of photocatalytic MO dyestUFF degradation was found to follow a pseudo-first-order rate law.
TL;DR: The special nanostep structure was observed at the surface of the sulfide photocatalyst, which was demonstrated to be crucial for the remarkable enhancement of photocatalytic hydrogen production.
Abstract: A novel method for the preparation of a CdS photocatalyst is presented. In this method, freshly prepared CdO obtained by decomposing cadmium acetate at a certain temperature was subjected to thermal treatment in the presence of H2S, which results in the formation of a highly stable and active CdS photocatalyst. In comparison to conventional preparation methods, CdS prepared by our method was found to be stable against both air oxidation and photocorrosion during a photocatalytic reaction. Most importantly, the special nanostep structure was observed at the surface of the sulfide photocatalyst, which was demonstrated to be crucial for the remarkable enhancement of photocatalytic hydrogen production. The apparent quantum yield at 420 nm and the energy conversion efficiency in the whole visible light region were determined to be 24.1% and 6.35%, respectively, in our experimental conditions.
TL;DR: In this paper, the photocatalytic activity of Cr-TiO2 was investigated for the degradation of XRG aqueous solution both under UV and visible light irradiation with an optimal doping concentration of 0.15% and 0.2%, respectively.
Abstract: Cr3+-doped anatase titanium dioxide photocatalysts were prepared by the combination of sol–gel process with hydrothermal treatment. The samples were characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area (SBET), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectroscopy and X-ray photoelectron spectroscopy (XPS). It was confirmed that Cr substitutes Ti4+ in TiO2 lattice in trivalent ionic state, and the concentrations of dopants Cr3+ decrease from the exterior to the interior of doped TiO2. The photocatalytic activity of Cr-TiO2 was investigated for the photocatalytic degradation of XRG aqueous solution both under UV and visible light irradiation. Due to the excitation of 3d electron of Cr3+ to the conduction band of TiO2, Cr-TiO2 shows a good ability for absorbing the visible light to degrade XRG. Doping of chromium ions effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.15% and 0.2%, respectively. The special distribution of dopants Cr3+ seems having a good effect on enhancing the photocatalytic activity of Cr-TiO2.
TL;DR: In this article, the photocatalytic activity of B-doped TiO2 nanoparticles was evaluated by the photoregeneration of reduced nicotinamide adenine dinucleotide (NADH).
Abstract: Boron-doped TiO2 nanoparticles were prepared by the sol−gel method and characterized by XRD, TEM, XPS, FT-IR, and UV−vis spectroscopy. XRD results showed that the doping of boron ions could efficiently inhibit the grain growth and facilitate the anatase-to-rutile transformation prior to the formation of diboron trioxide phase. FT-IR and XPS results revealed that the doped boron was present as the form of B3+ in B-doped TiO2 samples, forming a possible chemical environment like Ti−O−B. The lattice parameters at different boron contents and calcination temperatures indicated that B3+ was likely to weave into the interstitial TiO2 structure. The photocatalytic activity of the B-doped TiO2 nanoparticles was evaluated by the photoregeneration of reduced nicotinamide adenine dinucleotide (NADH). All B-doped TiO2 nanoparticles calcined at 500 °C showed higher photocatalytic activity than pure TiO2 sample in the photocatalytic reaction of NADH regeneration under UV light irradiation. When the molar ratio of B to ...
TL;DR: The photocatalytic activity of Fe-doped TiO(2) powders prepared by this method and calcined at 400 degrees 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.
TL;DR: Nanosized CdS coupled TiO2 nanocrystals were prepared by a microemulsion-mediated solvothermal method at relatively low temperatures as discussed by the authors, and the prepared samples were characterized by X-ray photoelectron spectroscopy (XPS), XPS, BET surface area analysis, XRD, and high-resolution transmission electron microscopy (HRTEM).
Abstract: Nanosized CdS coupled TiO2 nanocrystals were prepared by a microemulsion-mediated solvothermal method at relatively low temperatures The prepared samples were characterized by X-ray photoelectron spectroscopy (XPS), BET surface area analysis, X-ray diffraction (XRD), UV–vis absorption spectroscopy (UV–vis), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) It was found that the CdS coupled TiO2 materials consisted of uniform anatase TiO2 of 6–10 nm with highly dispersed cubic phase CdS nanocrystals The prepared samples exhibit strong visible light absorption at about 550 nm Meanwhile, they have high surface area in the range of 156–263 m2 g−1 and mesoporous character with the average pore diameter of ca 50–65 nm The coupling between the (1 0 1) crystal planes of anatase and (1 1 1) crystal planes of CdS was observed in the HRTEM image Ti3+ signal was observed in the electron paramagnetic resonance (EPR) spectrum of CdS coupled TiO2 nanocrystals under visible light irradiation It provided the evidence of an effective transfer of photo-generated electrons from the conduction band of CdS to that of TiO2 As expected, the nanosized CdS sensitized TiO2 nanocrystal materials showed enhanced activity in the oxidation of methylene blue in water or nitric oxide in air under visible light irradiation The mechanism of photocatalysis on CdS coupled TiO2 nanocrystals under visible light is also discussed
TL;DR: In this article, the authors address the various possibilities to couple heterogeneous photocatalysis with other technologies to photodegrade organic and inorganic pollutants dissolved in actual or synthetic aqueous effluents.
Abstract: Heterogeneous photocatalysis is a process of great potential for pollutant abatement and waste treatment. In order to improve the overall performance of the photoprocess, heterogeneous photocatalysis is being combined with physical or chemical operations, which affect the chemical kinetics and/or the overall efficiency. This review addresses the various possibilities to couple heterogeneous photocatalysis with other technologies to photodegrade organic and inorganic pollutants dissolved in actual or synthetic aqueous effluents. These combinations increase the photoprocess efficiency by decreasing the reaction time in respect to the separated operations or they decrease the cost in respect of heterogeneous photocatalysis alone, generally in terms of light energy. Depending on the operation coupled with heterogeneous photocatalysis, two categories of combinations exist. When the coupling is with ultrasonic irradiation, photo-Fenton reaction, ozonation, or electrochemical treatment, the combination affects the photocatalytic mechanisms thus improving the efficiency of the photocatalytic process. When the coupling is with biological treatment, membrane reactor, membrane photoreactor, or physical adsorption, the combination does not affect the photocatalytic mechanisms but it improves the efficiency of the overall process. The choice of the coupling is related to the type of wastewater to be treated. A synergistic effect, giving rise to an improvement of the efficiency of the photocatalytic process, has been reported in the literature for many cases.
TL;DR: It turned out that the visible-light absorption of this photocatalyst was due to the transition from the valence band consisting of O 2p orbitals to the conduction band, and the corner-sharing structure of the MoO(6) octahedra contributed to the visible light response and the photocatalytic performance.
Abstract: Aurivillius structure Bi2MoO6 (BG: 2.70 eV) that is a low-temperature phase showed an intense absorption band in the visible light region and photocatalytic activity for O2 evolution from an aqueous silver nitrate solution under visible light irradiation, among various bismuth molybdates (Bi2MoO6, Bi2Mo2O9, and Bi2Mo3O12) synthesized by solid-state and reflux reactions. Bi2Mo3O12 (BG: 2.88 eV) also showed photocatalytic activity for O2 evolution under full-arc irradiation of a Xe lamp (λ > 300 nm). The photocatalytic activity of the Aurivillius structure Bi2MoO6 prepared by the reflux method was dependent on the annealing temperature after the preparation. The crystallinity was the important factor for the activity. Calculation by the density functional method indicated that the conduction band of Aurivillius structure Bi2MoO6 was made up of Mo 4d orbitals. It turned out that the visible-light absorption of this photocatalyst was due to the transition from the valence band consisting of O 2p orbitals to...
TL;DR: An analysis of decomposition of methylene blue in an aerated aqueous solution by its action spectrum has shown that sulfur-doped titania (S-TiO 2 ) has activity under visible-light irradiation and that the decomposition mechanism depends on the excitation wavelength as discussed by the authors.
TL;DR: In this paper, the photocatalytic activity of as-prepared titanate nanotubes was evaluated by photocatalysis oxidation of acetone in air, and the effects of calcination temperature on the phase structure, crystallite size, morphology, specific surface area and pore structures of the titanate nano-blocks were investigated.
Abstract: Titanate nanotubes were prepared via a hydrothermal treatment of TiO2 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 TiO2 crystallites and the decrease of specific surface area and pore volume.
TL;DR: In this article, the photocatalytic performance of the nanocrystallite Bi2O3 was evaluated using methyl orange (MeO) as a model pollutant, and the results showed that such nanocrystite Bi 2O3 can effectively degrade 86% MeO within 100min under visible light illumination.
Abstract: The synthesis of Bi2O3 by a simple sonochemical route is investigated. Surfactant polyvinylpyrrolidone (PVP) has strong effects on the grain sizes and morphologies of Bi2O3. Bi2O3 single crystallite with grain size of 40–100 nm is obtained in the presence of 0.5 g PVP. X-ray diffraction (XRD) pattern shows that the nanocrystallite Bi2O3 is monoclinic and has a high degree of crystallinity. Optical characterizations show that the nanocrystallite Bi2O3 presents the photoabsorption properties from UV light region to visible light shorter than 470 nm and the band gap of the nanocrystallite Bi2O3 is 2.85 eV. The photocatalytic performance of the nanocrystallite Bi2O3 is evaluated using methyl orange (MeO) as a model pollutant. The photocatalytic results show that such nanocrystallite Bi2O3 can effectively degrade 86% MeO within 100 min under visible light illumination (λ > 400 nm). The action spectrum of MeO degradation over nanocrystallite Bi2O3 further confirms that the photocatalytic reaction can be driven by visible light. The photocatalytic mechanism is also studied based on electronic structure calculations using density functional theory (DFT).
TL;DR: The UV-A-induced photocatalytic oxidation over TiO2 suspensions was capable of decolorizing the effluent completely, as well as reducing chemical oxygen demand (COD) sufficiently, and it was found that ecotoxicity was fully eliminated following photocatallytic oxidation.
TL;DR: In this paper, a new group of photocatalyst materials for water splitting into H 2 and O 2 under ultraviolet light irradiation was described, including tantalates and alkali and alkaline earth tantalates.
TL;DR: The photoactivities of the as-prepared samples for the rhodamine-B photodegradation were investigated systematically in this paper, where the photoactivity of the catalyst in relationship with the hydrothermal temperature, the crystal and band structure were also discussed in detail.
Abstract: Nanosized Bi 2 WO 6 was synthesized by a hydrothermal crystallization process. The as-prepared samples were characterized by X-ray diffraction, Brunauer–Emmet–Teller surface area and porosity measurements, transmission electron microscopy, Raman spectra, and diffuse reflectance spectroscopy. The photoactivities of the as-prepared samples for the rhodamine-B photodegradation were investigated systematically. As a result, the sample prepared at 180 °C exhibited the highest photochemical activity under visible-light irradiation. The further experiments revealed that the catalyst was active in a wide spectral range. Density functional theory calculations suggested that the visible-light response was due to the transition from the valence band formed by the hybrid orbitals of Bi 6s and O 2p to the conduction band of W 5d. The photoactivity of the catalyst in relationship with the hydrothermal temperature, the crystal and band structure were also discussed in detail.
TL;DR: In this article, a chemically stable cubic spinel nanostructured CdIn2S4 prepared by a facile hydrothermal method is reported as a visible-light driven photocatalyst.
Abstract: Nanostructured photocatalysts with high activity are sought for solar production of hydrogen. Spinel semiconductors with different nanostructures and morphologies have immense importance for photocatalytic and other potential applications. Here, a chemically stable cubic spinel nanostructured CdIn2S4 prepared by a facile hydrothermal method is reported as a visible-light driven photocatalyst. A pretty, marigold-like morphology is observed in aqueous-mediated CdIn2S4, whereas nanotubes of good crystallinity, 25 nm in diameter, are obtained in methanol-mediated CdIn2S4. The aqueous- and methanol-mediated CdIn2S4 products show excellent photocatalytic activity compared to other organic mediated samples, and this is attributed to their high degree of crystallinity. The CdIn2S4 photocatalyst gives quantum yields of 16.8 % (marigold-like morphology) and 17.1 % (nanotubes) at 500 nm, respectively, for the H2 evolution reaction. The details of the characteristics of the photocatalyst, such as crystal and band structure, are reported. Considering the importance of hydrogen energy, CdIn2S4 will be an excellent candidate as a catalyst for “photohydrogen” production under visible light. Being a nanostructured chalcogenide semiconductor, CdIn2S4 will have other potential prospective applications, such as in solar cells, light-emitting diodes, and optoelectronic devices.
TL;DR: The results indicate that as-synthesized TiO2 nanostructures possessed higher photocatalytic activity than the commercial titania precursors from whence they were derived.
Abstract: A size- and shape-dependent morphological transformation was demonstrated during the hydrothermal soft chemical transformation, in neutral solution, of titanate nanostructures into their anatase titania counterparts. Specifically, lepidocrocite hydrogen titanate nanotubes with diameters of ∼10 nm were transformed into anatase nanoparticles with an average size of 12 nm. Lepidocrocite hydrogen titanate nanowires with relatively small diameters (average diameter range of ≤ 200 nm) were converted into single-crystalline anatase nanowires with relatively smooth surfaces. Larger diameter (>200 nm) titanate wires were transformed into analogous anatase submicron wire motifs, resembling clusters of adjoining anatase nanocrystals with perfectly parallel, oriented fringes. Our results indicate that as-synthesized TiO2 nanostructures possessed higher photocatalytic activity than the commercial titania precursors from whence they were derived.
TL;DR: X-ray photoelectron spectroscopy analysis results revealed that the Cr cations doped at the Sr2+ site were all trivalent state (Cr3+), while those doping at the Ti4+Site were mixed valent states (Cr2+ and Cr6+), and the different photocatalytic activities of H2 evolution are supposed to closely relate to the different valentStates in SrTiO3.
Abstract: Usually, SrTiO3 monodoped with Cr cations at the Ti4+ site hardly shows visible light photocatalytic activity. Revealing the origin of this issue is important for us to find an alternative approach to make SrTiO3 active under visible light irradiation. In this paper, two Cr-doped SrTiO3(Sr0.95Cr0.05)TiO3 and Sr(Ti0.95Cr0.05)O3were synthesized by a conventional solid-state reaction method, and their photophysical and photocatalytic properties were studied comparatively. It was found that both (Sr0.95Cr0.05)TiO3 and Sr(Ti0.95Cr0.05)O3 showed considerable absorption to visible light. However, their photocatalytic activities for H2 evolution from aqueous methanol solution under visible light irradiation were significantly different: the H2 evolution rate over (Sr0.95Cr0.05)TiO3 (∼21 μmol/h) was more than 100 times that over Sr(Ti0.95Cr0.05)O3 (∼0.2 μmol/h). X-ray photoelectron spectroscopy analysis results revealed that the Cr cations doped at the Sr2+ site were all trivalent state (Cr3+), while those doped ...