Ultraviolet-visible Diffuse Reflectance Spectra Research Articles

Ag/Tio2/AOF as an Easily Reused and Highly Active Catalyst for Dye Photo-Degradation

A novel TiO2 loaded with Ag photocatalyst covering on a modified fiber surface was prepared by coordination-hydrolysis combined with a photo-reduction process. Samples were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscope (SEM), X-ray photoelectron spectroscope (XPS) and ultraviolet visible diffuse reflectance spectra (UV-vis DRS). Compared with powder TiO2, the TiO2/amidoxime fiber (TiO2/AOF) and Ag/TiO2/amidoxime fiber (Ag/TiO2/AOF) exhibited a significant absorption edge of red-shift from ultraviolet to visible light region. The samples’ visible-light photodegradation activities were investigated and the results showed that the Ag/TiO2/AOFs exhibit excellent photocatalytic activities-about 99% decomposition rate of Rhodamine B with 100 minutes of visible light irradiation. The catalyst exhibits excellent catalytic activity and is easily recovered and reused.

The effects of Gd3+ doping on the physical structure and photocatalytic performance of Bi2MoO6 nanoplate crystals

Gd3+ doped Bi2MoO6 nanoplate crystals were fabricated by solvothermal combined calcination method. The effects of Gd3+ doping with different concentrations on the texture, crystal and optical properties of Bi2MoO6 were investigated by N2 physical adsorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet–visible diffuse reflection spectrum (UV–vis DRS), photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Under simulated solar light irradiation, the influences of Gd3+doping on photocatalytic activity of Bi2MoO6 were evaluated by photocatalytic degradation of Rhodamine B. The characterization results showed that with Gd3+ doping, a contraction of lattice and a decrease in crystallite size occurred. Meanwhile, an increase in surface area over Gd3+ doped Bi2MoO6 was observed. Moreover, Gd3+ doping could obviously enhance the visible light harvesting of Bi2MoO6 and promoted the separation of photogenerated electrons and holes. With optimum Gd3+(6wt%) doping, Gd/Bi2MoO6 exhibited the best activity and stability in degradation of Rhodamine B.

A P/N type compounded Cu2O/TiO2 photo-catalytic membrane for organic pollutant degradation

A heterojunction thin film consisting of n-type titanium dioxide (TiO2) and p-type cuprous oxide (Cu2O) was fabricated on an FTO conducting glass. The TiO2 films were grown on the FTO glass by sol–gel and spray pyrolysis methods, and Cu2O was deposited on it via the hydrothermal method. The morphology, crystalline structure, and optical absorption characteristics were studied by scanning electron microscopy, X-ray diffraction, and ultraviolet–visible diffuse reflectance spectrum, respectively. The results show that the surface of the Cu2O/TiO2 film was composed of net and large grains, which contributed to a large specific surface area. The crystal phase of the TiO2 in the Cu2O/TiO2 film remained anatase. The crystal phase of the Cu2O could not be detected as it is found in traces. The Cu2O/TiO2 film had a stronger optical absorption ability than the pure TiO2 film. To investigate catalytic activity, a photocatalytic degradation experiment of the Cu2O/TiO2 film was performed in a homemade thin-layer micro-reactor. The photocatalytic degradation of methylene blue increased with increasing amounts of deposited Cu2O until a maximum limit was reached. The photocatalytic activity might have declined with an increase in Cu2O content. The metallic oxide has the potential to screen other photocatalysts from the UV source.

Preparation of point-line Bi2WO6@TiO2 nanowires composite photocatalysts with enhanced UV/visible-light-driven photocatalytic activity

Bi2WO6@TiO2 nanowires composite photocatalysts (BWO-TNWS) with point-line structures have been successfully fabricated by hydrothermalsynthesis method, and characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectra (UV–vis DRS), photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The effects of coupling narrow-band-gap semiconductor Bi2WO6 (BWO) to photocatalytic activity for degrading Rhodamine B (RhB) and Phenol under UV–vis light irradiation were investigated. The results demonstrate that the photocatalytic activities of the prepared photocatalysts are associated with the content of Bi2WO6 (BWO). 20% BWO-TNWS (containing 20wt% BWO) composite exhibits the highest degradation rate for RhB and Phenol up to 78% and 33%, respectively. It can be concluded that the improved photocatalytic performance of the BWO-TNWS composite is mainly ascribed to its high photoinduced charge separation rate resulting from the effective heterojunction structure of BWO and TNWS, as well as the enlarged optical response range owing to coupling narrow-band-gap semiconductor BWO.

橄榄状BiVO<sub>4</sub>的制备及其可见光催化性能研究

本文以柠檬酸钠为络合剂，丙二酸为形貌控制剂，通过一步水热法制备了橄榄状BiVO4光催化剂。采用X-射线衍射(XRD)、扫描电子显微镜(SEM)以及紫外–可见漫反射(UV-Vis DRS)对材料的晶型、形貌以及吸收光谱进行表征，并以罗丹明B(RhB)为模拟降解污染物，测试BiVO4的可见光催化活性。结果表明：所制备的样品纯度高，为单斜晶相BiVO4，柠檬酸钠及丙二酸都对材料的形貌产生重要的影响。合成出的橄榄状BiVO4具有很强的可见光吸收能力，禁带宽度为2.36 eV，表现出最强的光催化活性。在500 W的氙灯激发下，2 h后，对罗丹明的降解率达到94%，并且所制备的样品具有良好的抗光腐蚀性，三次循环降解后，仍保持了92%的降解率。 Olive-like BiVO4 crystals were synthesized via a one-step hydrothermal method by using sodium citrate as the chelating agent and propane diacid as the shape control agent. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible diffuse reflectance spectrum (UV-Vis DRS) were employed to elucidate the structures, morphologies and the light absorption properties of the as-prepared BiVO4 samples. The photo-catalytic activities of BiVO4 crystals were evaluated by using rhodamine B (RhB) as simulative degradation pollutant. The results showed that all the samples possessed monoclinic structure and containing no any impurities. Both sodium citrate and propane acid have great influence on the morphologies of BiVO4 samples. The as-prepared olive-like BiVO4 samples had strong visible-light absorption abilities with the band gap value around 2.36 eV, and showed the highest photo-catalytic activities. The degradation rate of RhB could reach 94% after 2 h of irradiation with a 500 W Xe-illuminator. After three cycles of photo-catalytic degradation experiments, degradation rate still maintained 92%, which indicated that the olive-like samples had good resistant abilities to photocorrosion.

Preparation of Anatase TiO$lt;inf$gt;2$lt;/inf$gt; Nanocube with Exposed (001) Facet and Its Photocatalytic Properties

Anatase TiO2 single crystals with exposed (001) facets were successfully synthesized by a one-step hydro- thermal route using TiF4 as raw material. The crystal phase, morphology, microstructure, and photoabsorption of the samples were analyzed by field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS). The influences of hydrothermal temperature and pH of solution on morphology of TiO2 and exposure of (001) facets were also investi- gated. Photocatalytic catalysts was evaluated by degradation of acid red dye. Experimental results demonstrated that exposure of (001) facets was beneficial for improving photocatalytic performance. Under ultraviolet light irradiation, TiO2 nanocube with exposure of (001) facets ca. 33% exhibited significantly higher activity than the common TiO2 without exposed (001) facets. The photocatalytic efficiency of the former was 1.6 times as high as that of the latter. The sample with the highest exposure of (001) facets was obtained at hydrothermal temperature of 180 and pH of ℃

Novel visible-light-responsive Ag/AgCl@MIL-101 hybrid materials with synergistic photocatalytic activity

In this paper, a novel visible-light responsive photocatalyst of Ag/AgCl@MIL-101 was synthesized via vapor diffusion-photoreduction strategy. The as-prepared composite material was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, ultraviolet–visible diffuse reflection spectra and X-ray photoelectron spectroscopy. Due to the synergistic effect between Ag/AgCl and MIL-101, the composite photocatalyst exhibited an enhanced and stable photoactivity for the degradation of Rhodamine B under visible light irradiation. The relationship between the photocatalytic activity and the structure of Ag/AgCl@MIL-101 hybrid material was discussed and the possible reaction mechanism was proposed.

New method to synthesize mesoporous titania by photodegradation of surfactant template

Mesoporous titania has been successfully synthesized by photodegradation removal of cetyltrimethylammonium bromide as the surfactant, after slow hydrolyzation of titanium(IV) isopropoxide. Fourier transform infrared spectra proved that photodegradation has successfully decreased the peak areas of the alkyl groups from the template. The nitrogen adsorption analysis showed that the pore size and the specific surface area of the mesoporous titania were 3.7 nm and 203 m2 g−1, respectively, proving the mesoporosity of the titania obtained with the existence of the interparticle mesoporosity which was confirmed by transmission electron microscopy. Based on X-ray diffraction results, the mesoporous titania obtained was in the form of crystalline anatase phase. Furthermore, results from the diffuse reflectance ultra violet-visible spectra showed that the composition of tetrahedral titanium(IV) was more than the octahedral titanium(IV). When the mesoporous titania obtained was used as a catalyst in the oxidation of styrene, an improvement in the conversion of styrene (38%) was observed when compared to those obtained using Degussa P25 TiO2 (14%) as the catalyst.

Preparation of W and N, S-codoped titanium dioxide with enhanced photocatalytic activity under visible light irradiation

In this work, the preparation and physiochemical characterization of tungsten, nitrogen and sulfur codoping TiO2 photocatalysts (W, N, S-TiO2) was undertaken. W, N, S-TiO2 nanoparticles were synthesized via the precipitation-impregnation method. To investigate the structural, optical, and electronic properties, the as-prepared W, N, S-TiO2 photocatalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflection spectrum (DRS). W, N, S-TiO2 samples showed photo-absorption in the visible light region and higher visible light photocatalytic activity than TiO2. 0.011W, 0.030(N, S)-TiO2 exhibited the highest visible light photocatalytic activity, and the photocatalyic degradation activity of 0.011W,0.030(N,S)-TiO2 is nearly 10 times higher than that of TiO2. Compared with the undoped TiO2, the improved photocatalytic activity of W, N, S-TiO2 samples under visible light irradiation is attributed to the increase of the visible light absorption and the reduction in photogenerated electron-hole recombination.

Structure, morphology and opto-magnetic properties of Bi2MoO6 nano-photocatalyst synthesized by sol–gel method

Bismuth molybdate (Bi2MoO6) nano-particles (NPs) were synthesized using bismuth nitrate, ammonium molybdate, citric acid and ethyl cellulose by a simple sol–gel method. The structure, morphology, opto-magnetic and photocatalytic properties of the obtained powder were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, high resolution scanning electron microscopy (HRSEM), energy dispersive X-ray (EDX), ultraviolet–visible diffuse reflectance spectra (DRS), photoluminescence (PL) spectra and vibrating sample magnetometer (VSM) techniques. The XRD, FT-IR and EDX results indicate that the resultant powder is pure and single phase crystalline Bi2MoO6 with orthorhombic structure. The HRSEM image shows that the morphology of obtained powder consists with well defined nano-particles structure. The VSM results show superparamagnetic behavior of the obtained nano-particles. The photocatalytic activity of Bi2MoO6 nano-particles was performed. The addition of TiO2 catalyst enhances the photocatalytic activity of Bi2MoO6 nano-particles. The catalysts Bi2MoO6, TiO2 and mixed oxide catalyst Bi2MoO6–TiO2 nano-composites (NCs) were tested for the photocatalytic degradation (PCD) of 4-chlorophenol (4-CP). It is found that the PCD efficiency of Bi2MoO6–TiO2 NCs is higher than that of pure Bi2MoO6 and TiO2 catalysts.

Hydrothermal synthesis and characterization of In3+ modified BiVO4 nanoparticles with enhanced photocatalytic activity

In3+-doped BiVO4 nanoparticles with enhanced visible light activity have been successfully synthesized by a hydrothermal method. The synthesized materials were characterized by X-ray diffraction, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy, BET surface areas analysis, and ultraviolet–visible diffuse reflectance spectra. In comparison with pure BiVO4, the In3+-doped BiVO4 displayed greater photocatalytic activity in the degradation of methyl blue under visible light illumination. All samples possessed a single monoclinic structure. The introduction of In ions resulted in structural distortion and the decreased band gap energy, producing more electrons and holes for photocatalytic reaction. In the meantime, the doping In ions entails a red shift in the absorption edge and an increase in the intensity of light absorption. The best photocatalytic performance was obtained with the BiVO4 sample containing 5.0 mol% In ions.

HgI2: A novel photocatalyst with high performance in degradation of rhodamine B dyes under visible-light irradiation

A new photocatalyst, HgI2, was successfully developed. The HgI2 sample was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectrum (UV–vis DRS) and photoluminescence (PL) techniques. Its activity is as high as that of the highly efficient photocatalyst Ag3PO4 in degradation of rhodamine B (RhB) dyes under irradiation of visible light. It can be reused for at least three cycles without obvious loss of its activity in the degradation experiments. The main active species of HgI2 for the RhB degradation are superoxide anion radicals. The high photocatalytic activity of HgI2 may be attributed to its low recombination rate of the photogenerated carriers.

Broadband sensitized white light emission of g-C3N4/Y2MoO6:Eu3+ composite phosphor under near ultraviolet excitation

The g-C3N4/Y2MoO6:Eu3+ composite phosphors were synthesized and characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, ultraviolet visible diffuse reflection spectra, photoluminescence spectra and luminescence decay curves. Under the excitation of 360nm near ultraviolet light, these composite phosphors show tunable emission from blue to red region, in which white light emission can be obtained in term of appropriate quality proportion of Y2MoO6:Eu3+ relative to g-C3N4/Y2MoO6:Eu3+. In addition, the emission color can be also dependent on the excitation wavelength in g-C3N4/Y2MoO6:Eu3+ composite phosphor.

Preparation of titanium dioxide/tungsten disulfide composite photocatalysts with enhanced photocatalytic activity under visible light

Titanium dioxide/tungsten disulfide (TiO2/WS2) composite photocatalysts were fabricated via a one-step hydrothermal synthesis process, using TiCl4 as titanium source and bulk WS2 as sensitizer. The morphology, structure, specific surface area and optical absorption properties of the composite photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), specific surface area analyzer and ultraviolet-visible diffuse reflection spectrum (UV-vis DRS), respectively. The photocatalytic activity of as-prepared photocatalysts was evaluated by the degradation of methyl orange (MO) under illumination of 500W Xenon lamp. The results indicated that TiO2/WS2 composite photocatalysts possessed excellent photocatalytic activity, and ∼95% of the degradation rate for MO was reached when molar ratio of WS2 to TiO2 was 0.004 and the irradiation time was 60 min. Moreover, the carrier trapping experiment and fluorescence spectra showed that ·O 2 − was the key component in the photocatalytic degradation process and O2 was reduced to be ·O 2 − by the electrons from the conduction band of TiO2 and WS2 for the degradation of MO.

Photocatalytic hydrogen evolution and decomposition of glycerol over Cd0.5Zn0.5S solid solution under visible light irradiation

Cd0.5Zn0.5S solid solutions were prepared by hydrothermal method and co‐precipitation method. The synthesized materials were characterized by means of X‐ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area measurement and ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS). The photocatalytic activity was tested in the reaction of hydrogen evolution from aqueous solutions of glycerol under visible light irradiation (λ ≥ 420 nm). Zn0.5Cd0.5S‐G prepared by co‐precipitation method with glycerol as solvent exhibits higher photocatalytic activity. This can be due to Zn0.5Cd0.5S‐G possessing higher surface area, which is beneficial to the adsorption of electron donor on catalyst surface. Glycerol improves notably photocatalytic hydrogen evolution with its simultaneous degradation. The possible mechanism of photocatalytic reaction for hydrogen evolution with simultaneous glycerol degradation was discussed preliminary. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 141–148, 2016

CuS/MoS2 nanocomposite with high solar photocatalytic activity

Two-dimensional CuS/MoS2 heterostructure with high photocatalytic activity had been successfully obtained by a simple combination of wet chemical method and hydrothermal process. CuS nanosheets had been successfully grown on the two-dimensional MoS2 nanosheets uniformly and tightly. The obtained heterostructures were well characterized through X-ray diffraction patterns, transmission electron microscopy, Fourier transform infrared spectra, ultraviolet–visible diffuse-reflectance spectra, and Zeta potential measurement. Photocatalytic performance of the CuS/MoS2 nanocomposite was evaluated toward the decomposition of methylene blue solution under natural light. The as-prepared nanocomposite showed remarkably enhanced photocatalytic activity compared with pure CuS and MoS2. This could be attributed to the enhanced dyestuff absorption and charge transport after the conjugation between CuS and MoS2.

Hydrothermal synthesis of Graphene-TiO2 nanowire with an enhanced photocatalytic activity

The hydrothermal method was used to synthesize TiO2 nanowire (NW) and then fabricate graphene-TiO2 nanowire nanocomposite (GNW). Graphene oxide (GO) was prepared via improved Hummers’method. GO reduction to graphene and hybridization between NW and graphene by forming chemical bonding. The as-prepared composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM), and ultraviolet visible (UV-Vis) diffuse reflectance spectra. The photocatalytic activity was evaluated by the photodegradation of methylene blue (MB). The prepared GNW nanocomposite has superior photocatalytic activity in the degradation test, showing an impressive photocatalytic enhancement over NW. At the same time, in comparison with Graphene-TiO2 nanoparticle (NP) nanocomposite (GNP), GNW have a better activity which because NW have more uniform dispersion on graphene with less agglomeration.

Facile hydrothermal-carbonization preparation of carbon-modified Sb2S3 composites for photocatalytic degradation of methyl orange dyes

A series of carbon-modified antimony sulfide (Sb2S3) composites were prepared by facile hydrothermal-carbonization method using glucose as carbonaceous resource. The composites were characterized by X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectrum (UV–vis DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) techniques. The photocatalytic activity of the composites was tested in degradation of methyl orange (MO) dye under irradiation of visible light. The carbon content of the composites plays an important role in the photocatalytic degradation. The photocatalytic activity of carbon-modified Sb2S3 composites is higher than that of pure Sb2S3. The higher photocatalytic activity of the carbon-modified Sb2S3 photocatalysts can be attributed to their higher adsorption capacity and higher separation efficiency of photogenerated carriers.

Facile Synthesis of Ag@AgCl Plasmonic Photocatalyst and Its Photocatalytic Degradation under Visible Light

A facile synthesis for [email protected] plasmonic photocatalysts with high photocatalytic efficiency of organic pollutants under visible light was done by the precipitation-visible light irradiation method. The sample was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectra (DRS), and X-ray photoelectron spectroscopy (XPS). Photocatalytic degradation of methyl orange (MO) was carried out to evaluate the photocatalytic activity of [email protected] under visible light irradiation. It is found that the [email protected] photocatalyst shows a strong absorption in the visible region, which is attributed to the plasmon resonance of silver NPs deposited on AgCl particles. The photocatalytic reaction parameters, such as photoreduction time, dosage of catalyst and pH value were studied and optimized, and the highest activity for the degradation of methyl orange is up to 83% in 120 min under visible light irradiation. The excellent visible light photocatalytic activity can be attributed to the surface plasmon resonance effect of Ag NPs anchored on AgCl particles. The mechanism of separation of the photogenerated electrons and holes at the [email protected] photocatalyst were discussed.

Facile hydrothermal-carbonization approach to carbon-modified BiVO4 composites with enhanced photocatalytic activity

In this study, a series of carbon-modified BiVO4 composites were prepared by hydrothermal-carbonization method using glucose as carbonaceous resource. The composites were characterized by X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectrum (UV–vis DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) techniques. The photocatalytic activity of the composites was evaluated in degradation of methylene blue (MB) dye under irradiation of visible light. It was found that the carbon content of the composites plays an important role in the photocatalytic degradation, and the photocatalytic activity of carbon-modified BiVO4 composites is higher than that of pure BiVO4. The higher photocatalytic activity of the composites can be attributed to their higher adsorption capacity and higher separation efficiency of photogenerated carriers.