2O3 Photocatalyst Research Articles

Photocatalytic oxidative-extractive desulfurization of dibenzothiophene under simulated solar light with MoS2-CeO2/Al2O3-SiO2 nano photocatalyst: effect of CeO2 content

In this paper, a visible light-driven nanophotocatalyst of MoS2 with different amounts of CeO2 (0%, 8%, 16%, 24%, and 32% wt.) was impregnated on SiO2-Al2O3. The physicochemical properties of synthesized photocatalysts were investigated by XRD, FESEM, TEM, UV-Vis DRS, PL, BET-BJH, ICP-OES, EDX, and FTIR analyses. While the size of particles in all samples was in the nanoscale range, the sample with 8% wt. of CeO2 indicated the narrowest particle size distribution. UV-Vis DRS and PL analyses confirmed that adding CeO2 to the MoS2/SiO2-Al2O3 photocatalyst increased the amount of light absorption and decreased the recombination rate of charge carriers. Among CeO2-containing samples, the sample with 8% wt. of CeO2 illustrated the lowest recombination rate and the narrowest bandgap energy of 2.9 eV. The MoS2-CeO2/SiO2-Al2O3 photocatalyst with 8% wt. of CeO2 had the highest adsorption of DBT in dark conditions (29.93%), the highest photodegradation (96.9%) after 3 h of visible light irradiation and good stability after five consecutive runs. Meanwhile, total sulfur measurement indicated that using this sample and the extraction afterward, the model fuel has lost 96% of its sulfur content which confirms the excellent ability of acetonitrile-assisted extraction in gathering desulfurization products from the fuel.

Enhanced photo-degradation of diclofenac using a new and effective composite (O-g-C3N4/TiO2/α-Fe2O3): Degradation pathway, toxicity evaluation and application for real matrix

Removing persistent pharmaceutical compounds from wastewater, such as sodium diclofenac (DCF), has become challenging in recent years. This study aimed to introduce a simple and navel method for synthesizing a new O-g-C3N4/TiO2/α-Fe2O3 (OCNTF) photocatalyst and examine its performance in DCF degradation from aqueous solutions. During 60 min reaction time, a complete of 10 mg/L DCF was removed by a 1.0 g/L catalyst in a 40 ml DCF solution at pH 6.75 while 41.75% of total organic carbon (TOC) was removed under the same conditions. In the same situation, the photocatalytic efficiency for natural wastewater was 97.36% in 3 h. CO32- and HPO42- were the most to cause diclofenac degradation inhibited.A Mott-Schottky analysis, measurements of band edge location, and active species trapping were used to predict the mechanism of the S Scheme. •OH played an essential role in the photo-degradation of DCF by OCNTF and displayed excellent photocatalytic reactivity for DCF over 5 cycles. LC-MS was used to identify various intermediates formed during photocatalysis, and degradation pathways were investigated. In addition, the ECOSAR program predicted that UVA/OCNTF could be classified as an eco-friendly process. It has been shown that this catalyst can be considered for eliminating emerging pollutants from water environment.

A novel nano-heterojunction MoS2/α-Fe2O3 photocatalysts with high photocatalytic and photoelectrochemical performance under visible light irradiation

In this research successfully synthesized a novel heterojunction of MoS2 and α-Fe2O3 by hydrothermal method with special adjustments to the nanostructure for photocatalytic and photoelectrochemical (PEC) performance. The nano MoS2/α-Fe2O3 (nano MF) has an excellent surface area and great intrinsic edges, which can produce more active reaction sites. The advantage of this nanocomposite has certified by spectroscopic and characterizations approach. The results presented that for methylene blue (MB), nano MF photocatalysts revealed rather improved photocatalytic capability (∼98.5%) and the optimal transient photocurrent density (∼0.45 μA/cm2) with visible-light irradiation. These two analyses were three and nine folds larger than those displayed by the Fe2O3 sample, respectively. The photocatalytic degradation performance of nano-heterojunction photocatalysts improved due to increase reactive sites of the photocatalyst and reduced recombination of photo-induced carriers. The results reveal that the formation of a strong heterojunction between two semiconductors leads to the formation of the active photocatalyst. In this system, the generated superoxide radicals, holes and hydroxyl radicals with potential oxidation were operated to obtain superior efficient photodegradation of organic dyes. The fabricated nano MF samples indicated good stability, high reusability and wide utilization potential in photocatalytic and PEC processes. The present work has demonstrated the promising potential of nanocomposites for efficient photoelectrochemical and environmental remediation.

Novel pure α-, β-, and mixed-phase α/β-Bi2O3 photocatalysts for enhanced organic dye degradation under both visible light and solar irradiation

Combining the pure α- and β-phases of bismuth oxide enhances its photocatalytic activity under both visible and solar irradiation. α-Bi2O3, β-Bi2O3, and α/β-Bi2O3 were synthesized by a solvothermal calcination method. The structural, optical, and morphological properties of the as-synthesized catalysts were analyzed using XRD, UV-DRS, XPS, SEM, TEM, and PL. The bandgaps of α/β-Bi2O3, α-Bi2O3, and β-Bi2O3 were calculated to be 2.59, 2.73, and 2.34 eV, respectively. The photocatalytic activities of the catalysts under visible and solar irradiation were examined by the degradation of carcinogenic reactive blue 198 and reactive black 5 dyes. The kinetic plots of the degradation reactions followed pseudo-first-order kinetics. α/β-Bi2O3 exhibited higher photocatalytic activity (∼99%) than α-Bi2O3 and β-Bi2O3 under visible and solar irradiation. The TOC and COD results confirmed the maximum degradation ability of α/β-Bi2O3, and the decolorization percentage remained above 90%, even after five cycles under visible irradiation. The photocatalytic dye degradation mechanism employed by α/β-Bi2O3 was proposed based on active species trapping experiments.

Cascade electron transfer in ternary CuO/α-Fe2O3/γ-Al2O3 nanocomposite as an effective visible photocatalyst

Highly efficient ternary heterojunction of CuO/α-Fe2O3/γ-Al2O3 was effectively fabricated by a facile and cost effective chemical route. The structural, chemical composition, morphology, optical and photocatalytic properties of as-prepared CuO/α-Fe2O3/γ-Al2O3 photo catalyst were compared to pristine and binary samples by various characterization. Existence of all the dominant peaks of CuO, α-Fe2O3 and γ-Al2O3 are noticeable in XRD spectrum of CuO/α-Fe2O3/γ-Al2O3 ternary photo catalyst which confirms the successful formation of the photocatalyst. SEM and HRTEM results revealed the spherical shape CuO nanoparticles with distorted α-Fe2O3 agglomerated plates which led to complete diffusion with γ-Al2O3. The band gap of ternary nanocomposite was found to be 1.9 eV elucidated by UV-DRS. Brunauer-Emmett-Teller (BET) analysis showed that as-fabricated ternary CuO/α-Fe2O3/γ-Al2O3 nanocomposite exhibited the porous structure with large surface area and small pore volume as compared to pristine γ-Al2O3.due to the unique ternary nanocomposite structure and synergistic effect among various components. The photocatalytic activity was examined by monitoring the deterioration of methyl orange under simulated solar light irradiation. CuO/α-Fe2O3/γ-Al2O3 exhibited superior photocatalytic efficacy as compared to CuO/γ-Al2O3 and α-Fe2O3/γ-Al2O3 binary and pure oxides of γ-Al2O3, CuO and α-Fe2O3. The marvelous photocatalytic activity of CuO/α-Fe2O3/γ-Al2O3 ternary nanocomposite samples can be ascribed to their close contact, strong interfacial hybridization and proficient charge transfer capacity. The electrochemical studies such as linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were carried out to explore the charge transfer behavior and support the high photo activity of ternary nanocomposite CuO/α-Fe2O3/γ-Al2O3. LSV measurements manifested that CuO/α-Fe2O3/γ-Al2O3 exhibited 4.3 folds higher current density than bare γ-Al2O3 which confirmed the faster electron transfer from CuO to γ-Al2O3 via mediated α-Fe2O3 through the interfacial potential gradient in conduction band. Cyclic voltammetry (CV) results showed that pair of anodic and cathodic peaks in CuO/α-Fe2O3/γ-Al2O3 appeared which affirm the efficient increase in photo-induced e−/h+ separation and suppress recombination rate of electron-hole pair. This work demonstrated that CuO/α-Fe2O3/γ-Al2O3 ternary nanocomposite is found to be a promising candidate as an efficient adsorbent for organic dye removal from waste water.

Development of Cuboidal KNbO3@α-Fe2O3 Hybrid Nanostructures for Improved Photocatalytic and Photoelectrocatalytic Applications.

Monophasic and hybrid nanostructures of KNbO3 and α-Fe2O3 have been prepared using a hydrothermal process for photoelectrocatalytic and photocatalytic applications. Powder X-ray diffraction studies showed the formation of KNbO3, α-Fe2O3, and KNbO3/α-Fe2O3 with average grain sizes of 18.3, 11.5, and 26.1 nm and Brunauer–Emmett–Teller (BET) specific surface areas of 4, 100, and 20 m2/gm, respectively. Under simulated solar irradiation, the as-prepared heterostructure shows enhanced photoelectrocatalytic oxygen evolution reaction (OER) activity compared to pristine KNbO3 and α-Fe2O3. Significant photocatalytic activity of as-synthesized KNbO3/α-Fe2O3 heterostructure photocatalyst was obtained for removal of methylene blue organic dye under visible light, and the percentage activity was found to be 11, 49, and 89% for KNbO3, α-Fe2O3, and KNbO3/α-Fe2O3 photocatalysts, respectively. The dielectric constant was found to be 250.2, 65.2, and 251.5 for KNbO3, α-Fe2O3, and KNbO3/α-Fe2O3 heterostructure, respectively, at 50 °C and 500 kHz frequency.

Rational design of α-Fe2O3 nanocubes supported BiVO4 Z-scheme photocatalyst for photocatalytic degradation of antibiotic under visible light

The Z-scheme BiVO4/α-Fe2O3 photocatalyst was synthesized by a simple hydrothermal method. The photocatalyst is composed of α-Fe2O3 nanocubes with a regular cubic structure and the BiVO4 particles distributed on the surface of the α-Fe2O3 nanocubes. The photocatalytic performance of Z-scheme BiVO4/α-Fe2O3 photocatalyst was investigated in terms of its capacity for photodegradation of tetracycline hydrochloride. Improved photocatalytic activity was observed for Z-scheme BiVO4/α-Fe2O3 photocatalyst compared with pure BiVO4 and α-Fe2O3 nanocubes under visible light irradiation. Studies of its morphology, physicochemical properties and photoelectrochemical behaviors demonstrated that BiVO4 loading on the surface of α-Fe2O3 nanocubes forms a Z-scheme heterojunction, which increases the specific surface area and significantly promotes the separation of photoinduced carriers. The main active species were determined to be OH and h+ by ESR technique and trapping experiments. We propose a possible photocatalytic mechanism of Z-scheme BiVO4/α-Fe2O3 photocatalyst system. This study may also provide a novel and eco-friendly demonstration of a useful strategy for the design and preparation of special structure photocatalytic materials.

A novel immobilized Z-scheme P3HT/α-Fe2O3 photocatalyst array: Study on the excellent photocatalytic performance and photocatalytic mechanism

The Z-scheme photocatalyst is valuable for use in polluted water purification. To improve the practical application value of the Z-scheme, in this study, a nano α-Fe2O3 and P3HT composite photocatalyst array was synthesized by electrophoretic deposition for the first time. This material was named F1P. The EPR, VBXPS and in situ illumination XPS analyses indicated that the charge transfer path of F1P conforms to the Z-scheme, and F1P array has a high light energy conversion efficiency. Due to the advantages of the Z-scheme system and the good light harvesting ability, F1P exhibited a good degradation effect on different types of pollutants under visible light irradiation. The degradation efficiency of tetracycline and bisphenol A by F1P can reach 97 % and 99 %, respectively. Moreover, F1P showed a certain resistance to water quality changes. After four cycles, F1P can maintain the structural stability and good pollutant treatment effect. Due to the high redox ability of F1P, the complex structure of pollutants can be destroyed and the degradation path of pollutants in F1P system was also analyzed. This study provides a new way of synthesizing Z-scheme systems and immobilizing Z-scheme photocatalysts. F1P is a new material with high practicability.

Enriched silver plasmon resonance activity on the sonochemical synthesis of ZnO flowers with α-Fe2O3 as an efficient catalyst for photo-Fenton reaction and photo-oxidation of ethanol

We report the preparation of flower-shaped ZnO bunches with the α-Fe2O3 photocatalyst using the sonochemical method followed by the photodeposition of Ag nanoparticles. The Ag-ZnO/α-Fe2O3 photocatalyst was utilized for the removal of the environmental pollutant Methylene Blue (MB) dye. From our results, it was found that the Ag-ZnO/α-Fe2O3 photocatalyst exhibited higher photocatalytic activity when compared to ZnO/α-Fe2O3 with the addition of H2O2. Moreover, the higher plasmon resonance activity of the Ag with a photocatalyst degraded the MB dye within 30 min in the presence of H2O2. The different pH and the molar ratio of H2O2 were influenced by the degradation performance. In addition, the ZnO@α-Fe2O3 and Ag-ZnO/α-Fe2O3 photocatalysts were used for the generation of the OH radicals and the formation of formaldehyde and CO2 as analyzed by diffuse reflectance infra-red transmission (DRIFT) spectroscopy.

Plasmon Sensitized Heterojunction 2D Ultrathin Ag/AgI-δ-Bi2O3 for Enhanced Photocatalytic Nitrogen Fixation.

A novel 2D ultrathin Ag/AgI-δ-Bi2O3 photocatalyst was constructed by a facile hydrothermal and in situ photodeposition method, which presented a uniform nanosheet structure with an average height of 6 nm. Its composition, morphology and light-harvesting properties were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectrophotometer (UV–vis) and photoluminescence (PL) measurements in detail. The Ag/AgI-δ-Bi2O3 nanocomposites showed an excellent photocatalytic nitrogen fixation performance of 420 μmol L−1 g−1 h−1 in water without any sacrificial agent. The introduction of Ag/AgI nanoparticles caused the morphology modification of δ-Bi2O3, a higher concentration of oxygen vacancy, and the construction of a plasmon sensitized heterojunction, resulting in enhanced light absorption, improved separation efficiency of charge carriers and strong N2 absorption and activation ability, which are responsible for the superior photocatalytic performance of Ag/AgI-δ-Bi2O3.

Influence of ferroelectric dipole on the photocatalytic activity of heterostructured BaTiO3/a-Fe2O3

Using BaTiO3 as a model ferroelectric material we investigated the influence of the ferroelectric dipole on the photocatalytic activity of a heterogeneous BaTiO3/α-Fe2O3 photocatalyst. Two distinct BaTiO3 samples were used: BTO and BTO-A. The latter consists more ferroelectric tetragonal phase and thus stronger ferroelectricity. It was found that under identical experimental conditions, the photodecolourisation rate of a target dye using BTO-A/α-Fe2O3 under visible light was 1.3 times that of BTO/α-Fe2O3. Photoelectrochemical and photoluminescence analysis confirmed a more effective charge carrier separation in BTO-A/α-Fe2O3. Considering solely the photoexcitation of α-Fe2O3 in the composite photocatalysts under visible light and the similar microstructures of the two catalysts, we propose that the enhanced decolourisation rate when using BTO-A/α-Fe2O3 is due to the improved charge carrier separation and extended charge carrier lifetime arising from an interaction between the ferroelectric dipole and the carriers in α-Fe2O3. Our results demonstrate a new process to use a ferroelectric dipole to manipulate the charge carrier transport, overcome recombination, and extend the charge carrier lifetime of the surface material in a heterogeneous catalyst system.

In-situ fabrication of atomic charge transferring path for constructing heterojunction photocatalysts with hierarchical structure

The efficiencies of photocatalytic solar energy conversion systems are significantly limited by the challenging charge separation process, which can be improved via some commonly-used interfacial modulating strategies, e.g., introducing heterojunctions at the interfaces of different semiconductors. However, in many cases, the constructed heterojunctions not always work well mainly due to the serious mismatching of surface and energy structures between different components. In this study, inspired by the similarities in crystalline structures and elemental compositions, a novel heterojunction photocatalyst with hierarchical structure was first fabricated between bismuth-based semiconductors (Bi2Ti2O7 and γ-Bi2O3) possessing identical cubic phase via a simple in-situ transformation method. The resulted Bi2Ti2O7/γ-Bi2O3 heterojunction photocatalyst (denoted as BT/γ-Bi2O3) shows extremely high photocatalytic activities in photocatalytic removal of various high concentration environmental pollutants, e.g., phenol, dyes and sulfur containing compounds. An enhancement of more than two orders of magnitude in photocatalytic performances can be achieved for the BT/γ-Bi2O3 photocatalyst than the single composite, which is possibly attributable to the co-sharing of Bi-O tetrahedra units for the composites in heterojunction structures to provide an atomic charge transferring pathway for facilitating the spatial charge separation. This work provides an effective strategy for rationally constructing charge separation and transfer pathway in semiconductor-based photocatalysts for solar energy conversion.

Assembled composite of hematite iron oxide on sponge-like BiOCl with enhanced photocatalytic activity

Herein, sponge-like bismuthoxychloride (BiOCl) and hematite iron oxide (α-Fe2O3) were synthesized by simple and inexpensive method via two-step process, including hydrothermal and solution combustion method. The BiOCl/α-Fe2O3 composite photocatalysts were prepared by incorporating various weight ratios of α-Fe2O3 on BiOCl by a low-cost wet chemical process. The chemical interaction, phase and crystalline nature of the samples were ascertained by Fourier transform infrared spectroscopy (FT-IR) and x-ray diffraction (XRD). Further, the surface morphology and optical properties of the fabricated materials was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis diffuse reflection spectroscopy (DRS). Photocatalytic activities of the fabricated samples towards the photocatalytic degradation of direct red 81 (DR81) was evaluated under ultraviolet light illumination. The BiOCl/α-Fe2O3 composites showed remarkably enhanced photo-induced catalytic performances. The photocatalyst with optimal content of α-Fe2O3 with the highest photocatalytic performance was observed to 1%-BiOCl/α-Fe2O3. The synergistic improvement in the photodegradation of BiOCl/α-Fe2O3 sample may be because of an expansion in the noticeable light absorption efficiency as well as fast photo-generated charge separation. A probable mechanism for the photocatalytic degradation has been proposed for the catalytic performance of BiOCl/α-Fe2O3 photocatalyst.

Facile fabrication of multi-walled carbon nanotubes (MWCNTs)/α-Bi2O3 nanosheets composite with enhanced photocatalytic activity for doxycycline degradation under visible light irradiation

In this work, multi-walled carbon nanotubes (MWCNTs)/α-Bi2O3 nanosheets nanocomposites were firstly fabricated and used for photocatalytic degradation of doxycycline (DOX) under visible light. These nanocomposites were characterized by a series of techniques. XRD patterns illustrated α-Bi2O3 and MWCNTs/α-Bi2O3 composites were successfully synthesized. The nanotubular structure of MWCNTs and the nanosheet structure of α-Bi2O3 were determined by SEM and TEM. The compositional analysis of as-synthesized materials was obtained by XPS, and the results showed that MWCNTs and α-Bi2O3 were tightly combined. DRS spectra indicated that the introduction of MWCNTs broadened the light absorption range of the photocatalysts. The BET tests and photocatalysis experiments confirmed that the introduction of MWCNTs not only increases the specific surface area of the photocatalyst, but also increases its photocatalytic activity. When mass ratio of MWCNTs to α-Bi2O3 was 0.15, the catalyst showed the best degradation ability with 91% DOX was degraded at 120 min. The trapping experiments and electron spin resonance tests demonstrated that the ·O2− and ·OH radicals were the main reactive species in DOX degradation process. This work has prepared an economical MWCNTs/α-Bi2O3 photocatalyst by a simple solvothermal–calcination method, which has the potential application of pharmaceutical pollutants removal in water.

Photocatalytic Reduction of Chromium (VI) in a Typical Hides and Skin Industrial Wastewater using ZnO/γ-Al2o3 Photocatalyst under Visible LIGHT

Photocatalysis is an advanced oxidation process that can degrade and mineralize organic pollutants in wastewater to carbon dioxide and water which was employed in this study. Tannery effluent was treated via batch photoreduction using Zinc oxide photocatalyst supported on y-Al2O3 and irradiated under visible light at the ambient condition of temperature. Zinc oxide obtained from Zinc ore and y-Al2O3 prepared from local kaolin were used to synthesize the ZnO/y-Al2O3. The synthesized photocatalyst was characterized by Brunnaer Emmett Teller (BET), X-ray Diffraction Spectroscopy (XRD), Scanning Electron Microscope (SEM), and X-ray Fluorescence (XRF). The result of the analysis reveals that the total surface area, total pore volume and mean pore size of the photocatalyst prepared were 65.452 m2g-1, 0.151 cm3g-1 and 9.892 nm respectively. The photocatalyst is crystalline and the SEM image shows the presence of pores. The ZnO/y-Al2O3 was used as a photocatalyst to reduce Chromium (VI) of a typical tannery wastewater. 96% reduction of 20 mg/L of Cr (VI) was achieved at 60 min, pH of 3, and a photocatalyst dosage of 2.5 g/L under visible light of 400 W intensity. The kinetic study revealed that the photoreduction was fitted into the pseudo-first-order Lagmuir-Hinshelwood kinetic model. This research demonstrated that ZnO/y-Al2O3 photocatalyst was effective in the photoreduction of the selected response for the treatment of tannery wastewater.

Comparison of importance between separation efficiency and valence band position: The case of heterostructured Bi3O4Br/α-Bi2O3 photocatalysts

Heterostructured Bi3O4Br/α-Bi2O3 nanocomposites are prepared via in situ one-step self-combustion of ionic liquids. Tetrabutylammonium bromide (TBAB) is employed to be fuel, complexing agent for ionic liquids, as well as the reactant supplying Br for the objective material. The ratio of Bi3O4Br/α-Bi2O3 can be easily adjusted by controlling the amount of TBAB. The heterojunctions show higher photocatalytic ability towards both azo dye methyl orange (MO) and colorless pollutant phenol. The electron spin resonance (ESR) test and p-nitro blue tetrazolium chloride (NBT) degradation result indicate that generation amounts of superoxide anion radicals (O2−) over heterojunctions are less than that over pure Bi3O4Br. Photoelectrochemical measurements show that separation efficiencies of photo-generated electrons and holes are decreased after the combination of Bi3O4Br and α-Bi2O3. Work function test and scavenger experiments display that holes play key role for pollutant degradation and the position of holes on α-Bi2O3 is lowered via hybridization. Thus, the enhanced photocatalytic activity over composites can be attributed to the position decline of α-Bi2O3 valence band, thus improving the reactivity of holes in direct oxidation of pollutants. In this case, valence band position is confirmed to be more important than separation efficiency of charge carriers in affecting photocatalytic performance.

Enhanced Photocatalytic Activity of Heterostructured Ferroelectric BaTiO3/α-Fe2O3 and the Significance of Interface Morphology Control.

We have used a ferroelectric BaTiO3 substrate with a hematite (α-Fe2O3) nanostructured surface to form a heterogeneous BaTiO3/α-Fe2O3 photocatalyst. In this study we show that varying the mass ratio of α-Fe2O3 on BaTiO3 has a significant influence on photoinduced decolorization of rhodamine B under simulated sunlight. The highest photocatalytic activity was obtained for BaTiO3-Fe2O3-0.001M, with the lowest mass ratio of α-Fe2O3 in our study. This catalyst exhibited a 2-fold increase in performance compared to pure BaTiO3 and a 5-fold increase when compared to the higher-surface-area pure α-Fe2O3. The increases in performance become more marked upon scaling for the lower surface area of the heterostructured catalyst. Performance enhancement is associated with improved charge-carrier separation at the interface between the ferroelectric surface, which exhibits ferroelectric polarization, and the hematite. Increasing the mass ratio of hematite increases the thickness of this layer, lowers the number of triple-point locations, and results in reduced performance enhancement. We show that the reduced performance is due to a lack of light penetrating into BaTiO3 and to relationships between the depolarization field from the ferroelectric and carriers in the hematite. Our findings demonstrate that it is possible to use the built-in electric field of a ferroelectric material to promote charge-carrier separation and boost photocatalytic efficiency.

Synthesis and characterization of α/β-Bi2O3 with enhanced photocatalytic activity for 17α-ethynylestradiol

The α/β-Bi2O3 photocatalyst was successfully synthesized by a novel solvothermal-calcination method. The physical and chemical properties of as-prepared samples were characterized based on XRD, XPS, SEM, TEM, EDS, BET, UV–vis DRS and PL techniques. The synthesized α/β-Bi2O3 photocatalyst exhibited enhanced photocatalytic activity for 17α-ethinylestradiol (EE2), and 96.9% of EE2 was degraded after only 24min of visible-light irradiation using α/β-Bi2O3 as photocatalyst. The reaction rate constant over α/β-Bi2O3 photocatalyst was 1.42, 2.23, 9.22 and 54.1 times higher than pure β-Bi2O3, α-Bi2O3+β-Bi2O3, α-Bi2O3 and P25 respectively. Effect of catalyst dosage and pH value was investigated. The possible photocatalytic mechanism has been discussed on the basis of the theoretical calculation and the experimental results. α/β-Bi2O3 was a fairly stable and efficient photocatalyst under the studied experimental conditions, proving that the α/β-Bi2O3 photocatalyst was a promising photocatalyst for the practical application.

NOx abatement from stationary emission sources by photo-assisted SCR: Lab-scale to pilot-scale studies

In developing a higher activity for NOx abatement from stationary emission sources, photo-assisted selective catalytic reduction (photo-SCR) was systematically investigated over TiO2 supported on a spherical α-Al2O3/γ-Al2O3. The formation of NO2 was virtually suppressed in the reaction temperature range of 110–200°C. The NOx removal efficiencies of TiO2/γ-Al2O3 photocatalyst at 120°C for real flue gas (in pilot-scale photoreactor) and simulated flue gas (in lab-scale photoreactor) were 68–75% and 43.5%, respectively, in the presence of reducing reagent (C4H10). SEM and XPS techniques revealed that sulfur temporarily occupied the active sites of the photocatalyst, causing deactivation. Spent TiO2/γ-Al2O3 photocatalyst was regenerated via desulfurization by either air or hydrogen at 400–500°C. The effects of regeneration temperature and regeneration time on the photocatalytic activity are methodically investigated, demonstrating that using hydrogen at 500°C in 1h could completely regenerate the spent photocatalyst.

The synthesis, activity, stability and the charge transfer identification of Ag:AgBr/γ-Al2O3 photocatalyst for organic pollutant decomposition in water

Highly stable Ag:AgBr/γ-Al2O3 photo-catalyst was obtained by dispersing AgBr sol on hollow γ-Al2O3 microsphere. Metallic Ag nanoparticles were in situ generated on AgBr crystals by a photo-reduction method. The activity of catalyst was characterized by MO and phenol decomposition. The light irradiation response, the life times of the photo-induced charges, and the charge separation and transition were determined by the UV–vis diffuse reflection spectra, open circuit voltage decay spectra and transient photocurrent responses. The as-prepared Ag:AgBr/γ-Al2O3 catalyst can response to visible light irradiation. Charge separation was clarified to correlate with electrons transferring from Ag to AgBr surface and the consequent reaction with ads-O2 to generate O2− species. It was found that the O2− rather than OH played a dominant role in the photocatalytic oxidation of MO and phenol in water. However, the electrons trended to transfer from AgBr to Ag intrinsically without light irradiation. Therefore, the electron transfer between Ag and AgBr reaching the dynamic equilibrium was the key factor for obtaining a high stable Ag/AgBr catalyst which can be obtained by optimizing the Ag:AgBr ratio. Loading amount of Ag:AgBr on γ-Al2O3 was optimized to 30wt.% and the metallic Ag content was stabilized at 9wt.% of Ag:AgBr catalyst.