磁性光催化剂BiVO_4/Fe_3O_4降解亚甲基蓝的研究

本文用超声法将磁基体Fe3O4与BiVO4复合,制备了易于固液分离的磁性可见光催化剂BiVO4/Fe3O4,采用X射线衍射(XRD)、透射电子显微镜(TEM)等手段对样品的结构和形貌进行表征。以亚甲基蓝为降解对象,考察了BiVO4/Fe3O4的可见光催化活性,并研究了光催化体系中光催化剂用量、亚甲基蓝初始浓度、溶液的pH值、电子受体的存在对光催化过程的影响。结果表明,催化剂的最佳用量为2.0g/L,亚甲基蓝最佳初始浓度为10mg/L,溶液的最佳pH值为11,加入电子受体K2S2O8时,亚甲基蓝几乎完全降解。催化剂回收后连续使用3次,降解率仍然大于80%。     

Fe3O4／TiO2磁性催化剂的制备及在污水治理中的应用

以纳米Fe3O4为载体,以钛酸四丁酯为前躯体,用溶胶-凝胶法在Fe3O4表面包覆TiO2层,制备Fe3O4／TiO2光催化材料．透射电镜（TEM）、X射线衍射（XRD）、X射线光电子能谱（XPS）和红外光谱（IR）分析表明,TiO2在纳米Fe3O4颗粒表面形成很好的包覆层．用Fe3O4／TiO2光催化材料对工业上难处理...     

梯型BiVO4/Ag3VO4光催化剂的构建及其可见光光催化性能

近年来,有机污染物的问题变得越来越严重.为了解决该问题,人们研究和开发了许多有效的光催化剂.本工作采用水热法和化学沉积法合成了BiVO4/Ag3VO4梯型半导体材料,该复合材料在可见光下具有很强的氧化还原能力.其中40%BiVO4/Ag3VO4具有最佳的光催化降解性能,其降解速率为0.05588 min^-1,分别是BiVO4和Ag3VO4的22.76和1.76倍.并且其性能稳定,经过四次循环后其降解率仍可保持90%以上.BiVO4和Ag3VO4复合后,其催化性能得到增强,归因于形成了新型的梯型光催化机制,该方法促进了光生电荷的分离并延长了电荷的寿命,且通过PL测试和瞬态光电流响应证明了电荷的有效转移.X射线衍射(XRD)可以观察到Ag3VO4和BiVO4物相,没有其他成分.用扫描电子显微镜(SEM)和透射电子显微镜(TEM)进一步观察了该催化剂的结构和形貌,从SEM可以看出,Ag3VO4生长在BiVO4的上面,能谱分析也证明该催化剂仅包含Ag3VO4和BiVO4的各种元素,而不含其他杂质,TEM进一步证明了两种物质复合在一起,而不是机械混合.通过紫外-可见光漫反射光谱(UV-vis)测试可以得到BiVO4和Ag3VO4的吸收带边,进一步计算BiVO4的带隙和导带分别为2.41和0.455 eV,Ag3VO4的带隙和导带分别为2.20和0.04 eV,二者组成的异质结的带隙满足降解的条件.用荧光光谱(PL)和光电流研究了样品的光电特征,结果表明BiVO4/Ag3VO4光催化剂具有很高的载流子分离效率和很低的光电流电阻,这有助于光生载流子的运输.光催化降解甲基蓝实验表明,BiVO4/Ag3VO4具有很强的光催化降解速率(0.05588 min^-1),是BiVO4的22.6倍,Ag3VO4的1.76倍,而且经过四次循环后仍能保持很高的活性.通过XRD发现使用后的催化剂并没有发生变化,说明该催化剂具有良好的稳定性.高分辨X射线光电子能谱(XPS)不仅进一步说明了该催化剂成功复合后没有其他杂质元素,而且从各元素的结合能变化可以看出构成异质结后电子的流向,证实了光催化机制为梯型机制.光照射后,BiVO4和Ag3VO4产生电子空穴对,当催化剂受光激发后,电子从价带被激发到导带,并在价带留下空穴.当BiVO4和Ag3VO4复合后,在接触界面形成内电场,由于库仑相互作用,能带边缘弯曲等作用加速了Ag3VO4价带上某些空穴和BiVO4导带上电子的复合,从而阻止了Ag3VO4和BiVO4内部电子空穴对的复合,这有助于Ag3VO4导带上的电子和BiVO4价带上的空穴参与氧化还原反应.从捕获实验可以看出,本实验中空穴在光催化降解中起着最重要的作用,这与上述结论一致.     

Ordered mesoporous Pt/Fe3O4–CeO2 heterostructure gel particles with enhanced catalytic performance for the reduction of 4-nitrophenol

The unique physicochemical properties of ordered mesoporous transition metal oxides have attracted more and more attention. The hydrolysis process of metal oxide precursors is difficult to control, and it is difficult to synthesize an ordered mesoporous transition metal oxide material using the conventional template method. Ordered mesoporous Pt/Fe₃O₄–CeO₂ heterostructure gel materials with excellent catalytic properties were successfully prepared using aerogel technology and the chemical deposition method. The Pt/Fe₃O₄–CeO₂ material was an n–n combined heterostructured semiconductor material which consisted of a magnetic Fe₃O₄ layer, a CeO₂ core and Pt noble metal doped nanoparticles. A layer of Fe₃O₄ thin film was formed on the surface of ordered mesoporous Pt/CeO₂ gel matrix material using the chemical deposition method. The intriguing heterostructural features could facilitate reactant diffusion and exposure of active sites which could enhance synergistic catalytic effects between the Pt nanoparticles and CeO₂ nanoparticles. Compared with Pt/CeO₂, the prepared Pt/Fe₃O₄–CeO₂ showed enhanced catalytic activity in the reduction of 4-nitrophenol at room temperature. The catalytic activity of the heterostructure catalysts was systematically investigated using 4-nitrophenol reduction as a model reaction. The results showed that the Pt (0.1%)/Fe₃O₄–CeO₂ sample exhibited the optimal catalytic performance toward catalytic reduction of 4-nitrophenol to 4-aminophenol. The study provided a method for the preparation of heterostructure nanocatalysts with high efficiency, which would be effective for application in various catalytic reactions.     

Preparation,characterization and heterogeneous catalytic applications of GO/Fe3O4/HPW nanocomposite in chemoselective and green oxidation of alcohols with aqueous H2O2

Graphene oxide ‐ Fe₃O₄ ‐ NH₃⁺H₂PW₁₂O₄₀ ^‐ magnetic nanocomposite (GO/Fe₃O₄/HPW) was prepared by linking amino ‐ functionalized Fe₃O₄ nanoparticles (Fe₃O₄ ‐ NH₂) on the graphene oxide (GO), and then grafting 12 ‐ tungstophosphoric acid (H₃PW₁₂O₄₀) on the graphene oxide ‐ magnetite hybrid (GO ‐ Fe₃O₄ ‐ NH₂). The obtained GO/Fe₃O₄/HPW nanocomposite was well characterized with different techniques such as FT ‐ IR, TEM, SEM, XRD, EDX, TGA ‐ DTA, AGFM, ICP and BET measurements. The used techniques showed that the graphene oxide layers were well prepared and the various stages of preparation of the GO/Fe₃O₄/HPW nanocomposites successfully completed. This new nanocomposite displayed excellent performance as a heterogeneous catalyst in the oxidation of alcohols with H₂O₂. The as ‐ prepared GO/Fe₃O₄/HPW catalyst was more stable and recyclable at least five times without significantly reducing its catalytic activity.     

增强可见光催化活性的Z型MoO3/Bi2O4复合光催化剂的制备（英文）

全球工业化进程的加快使人们饱受环境污染问题的困扰.半导体光催化技术作为一种高效、绿色、有潜力的新技术,在环境净化方面有着广阔的应用前景.Bi2O4是近年来新开发出的一种铋基光催化剂,在环境净化方面已有一些研究.但是,单体光催化剂通常存在光响应范围窄、光生载流子复合率高等问题,这些不足限制了Bi2O4的进一步应用.因此,需要通过适当的改性来拓宽其光响应范围和提高其载流子的分离效率,从而提高其光催化活性.构建Z型异质结被认为是提高光催化剂光生载流子分离效率并进一步提高光催化活性的有效方法.MoO3是一种宽禁带的n型半导体,具有独特的能带结构、光学特性和表面效应,是一种非常有前景的半导体光催化剂.虽然MoO3材料的光生载流子复合率高,带隙(2.7-3.2 eV)大,不利于其参与光催化反应,但MoO3与其他合适的半导体配位形成复合材料后能够有效提高其光生载流子的分离效率,从而提高其光催化活性.本研究采用简单的水热法制备了一种新型Z型MoO3/Bi2O4复合光催化剂,SEM和TEM分析结果表明,MoO3和Bi2O4紧密结合在一起.X射线光电子能谱分析表明,MoO3和Bi2O4之间存在很强的界面相互作用,这有助于电荷转移和光生载流子的分离.光致发光光谱、电阻抗和光电流测试也证明了MoO3/Bi2O4复合光催化剂的光生载流子分离效率更高,形成了更强的光电流.通过在可见光下降解RhB溶液评价了所合成光催化剂的光催化性能.15%MoO3/Bi2O4(15-MB)复合光催化剂表现出了最佳的可见光催化活性,在40 min内对10 mg/L RhB溶液的降解率达到了99.6%,其降解速率是Bi2O4的2倍.此外,15-MB复合光催化剂在经过五次循环降解RhB溶液后仍保持良好的光催化活性和稳定性,表明MoO3/Bi2O4复合光催化剂具有较强的应用潜力.通过自由基捕获实验确定了光催化反应中主要的活性自由基为 O2-和h+.通过莫特-肖特基测试和带隙计算得到MoO3和Bi2O4的价带和导带位置.最后,根据实验和分析结果提出了Z型MoO3/Bi2O4复合光催化剂在可见光下降解RhB溶液的机理.本研究为设计铋基Z型异质结光催化剂用于高效去除环境污染物提供了一种有前景的策略.     

Magnetic retrievable Ag/AgBr/ZnFe2O4 photocatalyst for efficient removal of organic pollutant under visible light

In the present work, a visible-light-driven Ag/AgBr/ZnFe₂O₄ photocatalyst has been successfully synthesized via a deposition–precipitation and photoreduction method. The crystal structure, chemical composition, morphology and optical properties of the as-prepared nanocomposites were characterized by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscope, UV–vis diffuse reflectance spectroscopy and photoluminescence. The photocatalytic activities of the Ag/AgBr/ZnFe₂O₄ nanocomposites were evaluated through the photodegradation of gaseous toluene and methyl orange (MO) under visible light. The results revealed that the as-prepared Ag/AgBr/ZnFe₂O₄ nanocomposite exhibited excellent photocatalytic activity. The degrading efficiency of MO could still reach 90% after four cycles, and the Ag/AgBr/ZnFe₂O₄ nanocomposite could be recycled easily by a magnet. Additionally, the enhanced photocatalytic mechanism was discussed according to the trapping experiments, which indicated that the photo-generated holes (h⁺) and •O₂⁻ played important roles in photodegradation process. At last, a possible photocatalytic oxidation pathways of toluene was proposed based on the results of GC–MS. The Ag/AgBr/ZnFe₂O₄ composites showed potential application for efficient removal of organic pollutant.     

BiVO4/TiO2复合光催化剂的制备及可见光降解腐殖酸

首先以P123为模板剂利用溶胶-凝胶法制备TiO2载体,然后采用沉淀法制得介孔BiVO4/TiO2复合光催化剂.采用X射线衍射仪、漫反射吸收光谱仪、比表面分析仪对所制得的光催化剂进行了表征.结果表明,催化剂样品中的TiO2主要以锐钛矿型存在,BiVO4为四方相和单斜相共存的混晶,与单纯的BiVO4、TiO2光催化剂相比,BiVO4/TiO2复合光催化剂具有更高的可见光吸收性能、较好的比表面积和均一的介孔结构.腐殖酸的可见光降解试验表明,随着腐殖酸初始浓度的增大,其光降解率逐渐降低,ln(C/C0)对t呈线性关系.试验同步研究了腐殖酸光催化降解过程中荧光光谱、红外光谱和GC-MS谱图的变化情况.     

Synthesis of KIT-5 decorated by Bi2S3-Fe3O4 photocatalyst for degradation of parathion pesticide in aqueous media: Offering a degradation model and optimization using response surface methodology (RSM)

In this research, a novel KIT-5/Bi₂S₃-Fe₃O₄ nanocomposite was prepared. The structure and morphology properties of the nanocomposite were well characterized by XRD, FESEM-EDS-mapping, TEM, and N₂ adsorption–desorption. Benefiting from the visible light, the as-prepared KIT-5/Bi₂S₃-Fe₃O₄ nanocomposite exhibit significantly improved photocatalytic performance for the degradation of parathion. The optimum photocatalytic efficiency of KIT-5/Bi₂S₃-Fe₃O₄ nanocomposite was investigated with the central composite design using Design Expert software. The four critical variables affecting parathion degradation such as the concentration of parathion, pH, irradiation time, and amount of KIT-5/Bi₂S₃-Fe₃O₄ nanocatalyst. A polynomial function corresponding to degradation percent was obtained for the experimental data. The results showed that this catalyst has a good performance for the degradation of parathion.     

Hydrothermal Synthesis of g‐C3N4/NiFe2O4 Nanocomposite and Its Enhanced Photocatalytic Activity

Herein, for the first time, a direct Z‐scheme g‐C₃N₄/NiFe₂O₄ nanocomposite photocatalyst was prepared using facile one‐pot hydrothermal method and characterized using XRD, FT‐IR, DRS, PL, SEM, EDS, TEM, HRTEM, XPS, BET and VSM characterized techniques. The result reveals that the NiFe₂O₄ nanoparticles are loaded on the g‐C₃N₄ sheets successfully. The photocatalytic activities of the as‐prepared photocatalysts were evaluated for the degradation of methyl orange (MO) under visible light irradiation. It was shown that the photocatalytic activity of the g‐C₃N₄/NiFe₂O₄ nanocomposite is about 4.4 and 3 times higher than those of the pristine NiFe₂O₄ and g‐C₃N₄ respectively. The enhanced photocatalytic activity could be ascribed to the formation of g‐C₃N₄/NiFe₂O₄ direct Z‐scheme photocatalyst, which results in efficient space separation of photogenerated charge carriers. More importantly, the as‐prepared Z‐scheme photocatalyst can be recoverable easily from the solution by an external magnetic field and it shows almost the same activity for three consecutive cycles. Considering the simplicity of preparation method, this work will provide new insights into the design of high‐performance magnetic Z‐scheme photocatalysts for organic contaminate removal.     

TiO2/polyaniline composites： An efficient photocatalyst for the degradation of methylene blue under natural light

Polyaniline (PAn) sensitized nanocrystalline TiO_2 composites (TiO_2/PAn) were successfully prepared and used as an efficient photocatalyst for the degradation of dye methylene blue (MB).The results showed that PAn was able to sensitize TiO_2 efficiently and the composite photocatalyst could be activated by absorbing both the ultraviolet and visible light (λ:190～800nm),whereas pure TiO_2 absorbed ultraviolet light only (λ<380nm).Under the irradiation of natural light,MB could be degraded more efficiently on the TiO_2/PAn composites than on the TiO_2.Furthermore,it could be easily separated from the solution by simple sedimentation.     

A green and efficient method for synthesis of benzimidazoles using nano‐Fe3O4 in PEG‐400/H2O aqueous system under ambient conditions at room temperature

In this paper, a green and facile protocol was described which was efficient for synthesis of benzimidazoles using nano‐Fe₃O₄ catalyst with continuous bubbling of air as the oxidant in PEG‐400/H₂O aqueous system at room temperature. This protocol afforded the target products in good to excellent yields and the catalytic system could be recycled and reused without significant loss of catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd.     

Cu2O/reduced graphene oxide/TiO2 nanomaterial: An effective photocatalyst for azide-alkyne cycloaddition with benzyl halides or epoxide derivatives under visible light irradiation

Cu₂O/reduced graphene oxide/TiO₂ (Cu₂O/rGO/TiO₂) photocatalyst was synthesized under ultrasonic irradiation. The nanomaterial was identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, UV–vis absorption, and inductively coupled plasma optical emission spectroscopy (ICP-OES). The Cu₂O/rGO/TiO₂ photocatalyst was utilized in “click” reaction for the preparation of 1,4-disubstituted 1,2,3-triazoles via one pot multicomponent reaction of benzyl halide or epoxide derivatives with alkynes in presence of NaN₃ and triethylamine under visible light irradiation. The “click” reaction was performed under mild conditions affording good to excellent yields of the triazole compounds using low catalyst loading in short reaction times. The nanocomposite was recovered and recycled for five successive runs without a major diminution in its catalytic performance.     

Polypyrrole/Fe3O4/CNT as a recyclable and highly efficient catalyst for one‐pot three‐component synthesis of pyran derivatives

Polypyrrole (PPY)/Fe₃O₄/CNT has been synthesized and characterized by FT‐IR, TEM and SEM techniques and its catalytic activity has been evaluated in the synthesis of several series of pyran derivatives. Tetrahydrobenzo[b]pyranes, 4H‐pyran‐3‐carboxylates, 4H,5H‐pyrano[3,2‐c]chromenes and dihydropyrano[2,3‐c]pyrazoles have been successfully prepared from one‐pot three‐component condensation of aldehyde, malononitrile and active methylene‐containing compounds (dimedone /ethyl acetoacetate/4‐hydroxycoumarin/3‐methyl‐2‐pyrazoline‐5‐one) using PPY/Fe₃O₄/CNT as a new and reusable heterogeneous catalyst. The present method offer several advantages such as; high yields of products, short reaction times, easy work‐up procedure and easy separation of the catalyst from the reaction mixture due to its magnetic character. Furthermore, chemoselective synthesis of bis‐benzo[b]pyran from terephthalaldehyde can be achieved by this method.     

Au与Fe_3O_4纳米微粒共嵌TiO_2纳米纤维的制备及可见光催化性能

通过静电纺丝法制备出含有Fe3O4纳米微粒的TiO2纳米纤维,再采用浸渍还原法将Au纳米微粒嵌入到TiO2纳米纤维上,制备出一种具有较强磁性和良好可见光响应能力的复合光催化材料.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和紫外-可见固体漫反射光谱仪(UV-VisDRS)等对样品的结构和形貌进行表征,并以降解罗丹明B(RhB)为模型反应,考察了样品在可见光照射下的光催化性能.结果表明,嵌入Au纳米微粒可使复合纳米纤维在可见光下降解RhB时表现出非常好的降解速率和降解率;同时,将Fe3O4纳米微粒嵌入TiO2纳米纤维内部可以赋予材料较强的磁性,使材料便于分离和重复利用.     

A Novel Biomimetic Hydrogen Peroxide Biosensor Based on Pt Flowers‐decorated Fe3O4/Graphene Nanocomposite

A sensitive and selective amperometric H₂O₂ biosensor was obtained by utilizing the electrodeposition of Pt flowers on iron oxide‐reduced graphene oxide (Fe₃O₄/rGO) nanocomposite modified glassy carbon electrode (GCE). The morphology of Fe₃O₄/rGO and Pt/Fe₃O₄/rGO was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The step‐wise modification and the electrochemical characteristics of the resulting biosensor were characterized by cyclic voltammetry (CV) and chronoamperometry methods. Thanks to the fast electron transfer at the Pt/Fe₃O₄/rGO electrode interface, the developed biosensor exhibits a fast and linear amperometric response upon H₂O₂. The linear range of Pt/Fe₃O₄/rGO is 0.1∼2.4 mM (R²=0.998), with a sensitivity of 6.875 μA/mM and a detection limit of 1.58 μM (S/N=3). In addition, the prepared biosensor also provides good anti‐interferent ability and long‐term stability due to the favorable biocompatibility of the electrode interface. The proposed sensor will become a reliable and effective tool for monitoring and sensing the H₂O₂ in complicate environment.     

Synthesis,characterization, and catalytic application of Fe3O4‐Si‐[CH2]3‐N=CH‐aryl for the efficient synthesis of novel poly‐substituted pyridines

Fe₃O₄ magnetic nanoparticles (MNPs) were functionalized by aminopropylsilane and reacted with aromatic aldehyde, and Fe₃O₄‐Si‐[CH₂]₃‐N=CH‐Aryl and Fe₃O₄‐Si‐(CH₂)₃‐NH‐CH₂‐Aryl MNPs were prepared as novel magnetic nanocatalysts. Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM) were used to identify the MNPs. The catalytic activity of the MNPs was evaluated in the one‐pot synthesis of some novel poly‐substituted pyridine derivatives.     

Sb2O3／TiO2纳米复合物的合成及性质研究

以改进的溶胶-凝胶法制备了Sb2O3／TiO2纳米复合物,用扫描电镜、X射线粉末衍射、傅立叶红外光谱、紫外-可见光谱以及荧光等测试技术对产物进行了分析和表征．结果表明：所得纳米复合物颗粒分散均匀,具有锐钛矿相结构,平均粒径约为10nm．还研究了所得产物的光催化性质、电化学性质及电化学发光行为．结果表明：Sb2O3的掺入可以提高TiO2的光催化效果,当反应物中m（Sb2O3）／m（TiO2）=10％时,所得纳米复合物对亚甲基蓝和罗丹明B的光催化效果最好．     

Inactivation of Escherichia coli on Immobilized CuO/CoFe2O4‐TiO2 Thin‐Film under Simulated Sunlight Irradiation

Composite photocatalysts of CuO/CoFe₂O₄‐TiO₂ were successfully synthesized by a sol‐gel method and fixed on ordinary tiles. The photosterilization of Escherichia coli was examined on CuO/CoFe₂O₄‐TiO₂ thin films under a xenon lamp irradiation. The film was characterized by XRD, and the morphology was observed by SEM. Disinfection data indicated that CuO/CoFe₂O₄‐TiO₂ composite photocatalysts have the much better photocatalytic activity than CuO/CoFe₂O₄ and TiO₂. The optimized composition of the nanocomposites has been found to be m_CuO/CoFe2O4:m_TiO2=3:7, with loadings ranging from 790 to 1400 mg/m². The photocatalytic inactivated rate of E. coli (10⁵ CFU/mL) reached 98.4% under the xenon lamp of 150 W within 30 min.     

Synthesis,characterization and catalytic performance of core‐shell structure magnetic Fe3O4/P(GMA‐EGDMA)‐NH2/HPG‐COOH‐Pd catalyst

A strategy has been developed for the synthesis, characterization and catalysis of magnetic Fe₃O₄/P(GMA‐EGDMA)‐NH₂/HPG‐COOH‐Pd core‐shell structure supported catalyst. The P(GMA‐EGDMA) polymer layer was coated on the surface of hollow magnetic Fe₃O₄ microspheres through the effect of KH570. The core‐shell magnetic Fe₃O₄/P(GMA‐EGDMA) modified by ‐NH₂ could be grafted with HPG. Then, the hyperbranched glycidyl (HPG) with terminal ‐OH were modified by ‐COOH and adsorbed Pd nanoparticles. The hyperbranched polymer layer not only protected the Fe₃O₄ magnetic core from acid–base substrate corrosion, but also provided a number of functional groups as binding sites for Pd nanoparticles. The prepared catalyst was characterized by UV–vis, TEM, SEM, FTIR, TGA, ICP‐OES, BET, XRD, DLS and VSM. The catalytic tests showed that the magnetic Fe₃O₄/P(GMA‐EGDMA)‐NH₂/HPG‐COOH‐Pd catalyst had excellent catalytic performance and retained 86% catalytic efficiency after 8 consecutive cycles.