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1.
Ag nanoparticle (NP)‐decorated MIL‐125(Ti) microspheres (Ag@MIL‐125(Ti)) were firstly fabricated via a facile hydrothermal and following photo‐reduction method. The photocatalysts were characterized using X‐ray diffraction, scanning and transmission electron microscopies, X‐ray photoelectron spectroscopy and UV–visible diffuse reflectance spectroscopy. The characterization results indicated that Ag NPs were dispersed on the surface of MIL‐125(Ti) microspheres, and the Ag NPs had a uniform diameter of about 40 nm. The composites exhibited excellent visible‐light absorption, due to the modification with the Ag NPs. The photocatalytic activity for the visible‐light‐promoted degradation of Rhodamine B was improved through the optimization of the amount of Ag loaded as a co‐catalyst, this amount being determined as 3 wt%. Additionally, studies performed using radical scavengers indicated that O2? and e? served as the main reactive species. The catalyst can be reused at least five times without significant loss of its catalytic activity. Furthermore, a photocatalytic mechanism for degradation of organics over Ag@MIL‐125(Ti) is also proposed. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

2.
A novel visible‐light‐driven g‐C3N4/MIL‐53(Al) composite photocatalyst was successfully prepared using a facile stirring method at room temperature. The g‐C3N4/MIL‐53(Al) composites were characterized and their effects on the photocatalytic activities for rhodamine B degradation were investigated. The g‐C3N4(20 wt%)/MIL‐53(Al) photocatalyst displayed optimal photocatalytic degradation efficiency, which was about five times higher than the photocatalytic activity of pure g‐C3N4. The improved photocatalytic performance of the g‐C3N4/MIL‐53(Al) photocatalyst was predominantly attributed to the efficient separation of electron–hole pairs and the low charge‐transfer resistance. g‐C3N4/MIL‐53(Al) also exhibited excellent stability and reusability. A proposed mechanism for the enhanced photocatalytic activity is also discussed based on the experimental results. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

3.
In recent years, tremendous research efforts have been made towards developing metal–organic framework (MOF)‐based composites for photocatalytic applications. In this work, bipyramid‐like MIL‐125(Ti) frustum enwrapped with reduced graphene oxide (rGO) and dispersed silver nanoparticles (Ag NPs) was fabricated using an efficient one‐pot self‐assembly and photoreduction strategy. The as‐obtained materials were characterized using field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, nitrogen adsorption–desorption isotherms, and X‐ray photoelectron, ultraviolet–visible diffuse reflectance and photoluminescence spectroscopies. It is found that the as‐prepared Ag/rGO/MIL‐125(Ti) ternary hybrids have large surface area, microporous structure, enhanced visible light absorption and prolonged lifetime of charge carriers. Compared with pure MIL‐125(Ti) and its binary counterparts, the ternary composite exhibits more efficient photocatalytic performance for Rhodamine B (RhB) degradation from water under visible light irradiation. The photodegradation rate of RhB on Ag/rGO/MIL‐125(Ti) is 0.0644 min?1, which is 1.62 times higher than that of the pure MIL‐125(Ti). The improved photocatalytic performance is ascribed to the indirect dye photosensitization, the Ag NP localized surface plasmon resonance, the Ti3+–Ti4+ intervalence electron transfer and the synergistic effect among MIL‐125(Ti), Ag NPs and rGO. Ag NPs serve as an efficient ‘electron reservoir’ and rGO as an electron transporter and collector. Therefore, this work provides a new pathway into the design of MOF‐based composites for application in environmental and energy fields. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

4.
通过简单溶剂热法制备了一种新型复合光催化剂BiVO_4/M IL-53(Fe);运用XRD、SEM/EDS、FT-IR、N_2吸附-脱附和UV-vis DRS等手段对其进行表征,并对其光催化降解RhB活性进行了研究,提出了相应的光催化降解RhB的可能机理。结果表明,相较于单一BiVO_4材料,复合催化剂的比表面积增大,且其光催化效率相较于纯BiVO_4和MIL-53(Fe)也有了较大的提高;其中,BF-2复合材料的光催化活性最高,分别约为纯MIL-53 (Fe)和BiVO_4的5. 2倍和8. 1倍。同时,BiVO_4/MIL-53(Fe)复合光催化剂经过四次循环实验后,仍能保持较稳定的光催化活性和结构。  相似文献   

5.
A metal–organic framework material, MIL‐125(Ti), was solvothermally prepared and characterized using X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and surface area measurements. MIL‐125(Ti) was then used as an adsorbent for Rhodamine B (RhB) removal in aqueous solution. The adsorption kinetics, adsorption mechanism, adsorption isotherm, activation energy and various thermodynamic parameters were studied in detail. The maximum adsorption capacity of MIL‐125(Ti) for RhB was 59.92 mg g?1. MIL‐125(Ti) appears to be a promising material for RhB adsorption from aqueous solutions. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

6.
胡蕾 《分子催化》2013,27(4):377-384
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.  相似文献   

7.
Photocatalytic activity of titanium(IV) oxide (TiO2) can be enhanced through modification of its surface‐active sites. Here, iron(III) carboxylate [MIL‐53[Fe]]‐incorporated TiO2 (as MIL‐53(Fe)/TiO2) was prepared using a hydrothermal method. This material was then calcined at 500°C to obtain a MIL‐53(Fe)‐derived γ‐Fe2O3/TiO2 photocatalyst. A photocatalytic study of MIL‐53(Fe)/TiO2 and MIL‐53(Fe)‐derived γ‐Fe2O3/TiO2 toward cationic methylene blue (MB) and anionic methyl orange (MO) showed that MIL‐53(Fe)/TiO2 (0.25 wt%) and MIL‐53(Fe)‐derived γ‐Fe2O3/TiO2 (0.75 wt%) resulted the best degree of dye degradation. The MIL‐53(Fe)‐derived γ‐Fe2O3/TiO2 (0.75 wt%) composite for instance is capable of degrading almost 100% of 20‐ppm MB and MO, respectively, within 6 hr. Photocatalytic degradation of MB and MO was well fitted to the Langmuir‐Hinshelwood pseudo‐first order kinetics model, which indicates physisorption as the key partway that facilitates dye decomposition on the surface of a photocatalyst under UV‐A irradiation. This study provides new insights into the exploration of MILs/TiO2 materials for the environmental remediation and pollution control.  相似文献   

8.
From previous reports, graphitic carbon nitride (g‐C3N4) can be used as a photocatalyst, although the low efficiency of solar energy utilization, small specific surface area and high recombination rate of photogenerated electron–hole pairs limit its practical application. For the purpose of increasing photocatalytic activity, especially under irradiation of visible light, we successfully synthesized a new composite, namely porous g‐C3N4/Ag/Cu2O, through chemical adsorption of Ag‐doped Cu2O on porous g‐C3N4, which has not been investigated carefully worldwide. The composition, morphology and optical properties of the composite were investigated through methods including X‐ray diffraction, energy‐dispersive X‐ray, Fourier transform infrared, UV–visible and photoluminescence spectroscopies and transmission electron microscopy. Using rhodamine B as organic pollutant to be degraded under the irradiation of visible light, different mass ratios of Ag/Cu2O doped on porous g‐C3N4 led to enhanced photocatalytic performance of the composite compared to pure porous g‐C3N4. When the mass ratio of Ag/Cu2O is 15%, porous g‐C3N4/Ag/Cu2O exhibits a degradation rate 2.015 times higher than that of pure porous g‐C3N4. The reasons for this phenomenon may be attributed to the increased utilization efficiency of visible light, high‐speed separation of photogenerated electron–hole pairs, accelerated interfacial transfer process of electrons and increased surface area of the composite. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

9.
Acid‐treated g‐C3N4‐Cu2O was prepared by hydrothermal reduction followed by high temperature calcination and acid exfoliation. The structures and properties of as‐synthesized samples were characterized using a range of techniques, such as X‐ray photoelectron spectroscopy, scanning electron microscopy, Photoluminescence Spectroscopy and the Brunauer–Emmett–Teller (BET) theory. The photocatalytic activity was evaluated by measuring the photodegradation of methyl orange under visible‐light irradiation. Based on the results of TEM, XPS, EPR and other techniques, it was verified that a heterojunction was formed. The acid treatment process can increase the specific surface area to form abundant heterojunction interfaces as channels for photo‐generated carrier separation, thereby enhancing its light utilization and quantum efficiency. Results indicate that acid‐treated g‐C3N4‐Cu2O possesses a large specific surface area, which provides plentiful activated sites for heterojunctions to form; in addition, it showed a high visible light effect and the minimum charge‐transfer resistance. Furthermore, the g‐C3N4‐Cu2O material exhibits high levels of effectiveness and stability. Electron paramagnetic resonance and a series of radical trapping experiments demonstrate that the holes and ?O2? could be the main active species in methyl orange photodegradation. This work could provide new insights into the fabrication of composite materials as high‐performance photocatalysts, and facilitate their application in addressing environmental protection issues.  相似文献   

10.
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.  相似文献   

11.
Semiconductor‐based photocatalysis is an environmental friendly and cost‐effective technique for water treatment. Due to their unique properties, metal–organic frameworks (MOFs) are considered as ideal platform to develop composite photocatalyst. In this study, Bismuth oxychloride (BiOCl) was first attempt to be incorporated with highly stable MOFs, UiO‐66(Zr) by hydrothermal reaction. Different characterization methods including X‐ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscope, X‐ray photoelectron spectroscopy had been used to prove the successful synthesis of composite photocatalyst. The resultant BiOCl/UiO‐66 composite showed higher photodegradation performance of Rhodamine B (RhB) under ultraviolet and visible light irradiation than that of pristine materials and their mechanically mixed sample. In addition, the composite exhibited good structural stability and reusability. The photocatalytic mechanism of RhB degradation over the composite under visible light proceeded via a photosensitization process. A better adsorptivity of RhB and effective electron transfer within the hybrid material might be responsible for the enhanced photocatalytic performance.  相似文献   

12.
Novel F‐doped Ag/AgBr photocatalysts containing various amounts of F? were synthesized by an ion exchange method. The photocatalysts were characterized using X‐ray diffraction (XRD), scanning and transmission electron microscopies, X‐ray photoelectron, ultraviolet–visible absorption and photoluminescence spectroscopies and electron spin resonance (ESR). Powder XRD revealed that F? was inserted into the crystal lattices of AgBr and partially replaced Br?, resulting in the contraction of the AgBr lattices. Methyl orange photodegradation experiments showed that the photocatalytic activity of F‐doped Ag/AgBr was significantly dependent on the amount of F?. Ag/AgBr doped with 0.02 M F? achieved the highest activity of 91% after 8 min. ESR showed the main active species in methyl orange degradation was ?OH. The main enhancement mechanism is that F? inhibits the recombination of electron–hole pairs.  相似文献   

13.
Plasmonic Ag/AgCl‐modified bismuth subcarbonate (Bi2O2CO3) composites were prepared by a multistep process with hydrothermal, deposition, and photoreduction in the absence of organic capping agents. The properties of the obtained Ag/AgCl/Bi2O2CO3 samples were characterized using X‐ray diffraction, field emission scanning electron microscopy and X‐ray photoelectron, UV–visible diffuse reflectance, and photoluminescence spectroscopies. The results reveal that Ag/AgCl nanoparticles are dispersed on the Bi2O2CO3 surface to achieve plasmonic Ag/AgCl/Bi2O2CO3. The Ag/AgCl/Bi2O2CO3 nanocomposites show improved rhodamine B (RhB) adsorption capacity and photocatalytic activity compared with pure Bi2O2CO3 and Ag/AgCl. In addition, the Ag/AgCl/Bi2O2CO3 composite with 20 wt% Ag/AgCl exhibits the highest photocatalytic activity and remains stable for the photodegradation of RhB under visible light. The enhanced photocatalytic activity of Ag/AgCl/Bi2O2CO3 may be attributed to the surface plasmon resonance effect of in situ generated Ag nanoparticles and synergistic effect of Ag/AgCl and Bi2O2CO3, which increase the separation efficiency of photogenerated electron–hole pairs under visible light irradiation.  相似文献   

14.
太阳能是一种清洁的可再生能源,其中,可见光占太阳能总能量的45%。发展可见光响应的光催化剂是光催化领域重要的研究内容之一。NH2-MIL-125(Ti)是一种有代表性的金属有机骨架可见光催化剂,但其存在可见光利用效率不高、光生电子-空穴对复合快等缺点。近年来,研究者们通过对NH2-MIL-125(Ti)的晶面、结构和组成进行调控和修饰,提高其可见光催化活性。本文对近年来报道的关于提高NH2-MIL-125(Ti)可见光催化活性的方法进行了综述,并对NH2-MIL-125(Ti)基可见光催化剂的发展方向提出了建议,以期为NH2-MIL-125(Ti)在光催化反应中进一步应用研究提供参考。  相似文献   

15.
A novel and simple approach for the efficient and rapid synthesis of pyrano[2,3‐c]‐pyrazoleshas been accomplished via the four‐component condensation reaction of malononitrile, hydrazine hydrate, ethyl acetoacetate, and substituted aldehydes using MIL‐53(Fe) metal–organic framework (MOF) as a catalyst in ethanol at room temperature. Recycling studies have shown that the MIL‐53(Fe) can be readily recovered and reused six times without significant loss of its activity. The present protocol offers the advantages including short reaction times, simple workup, high yields, elimination of toxic solvents, no chromatographic purification and recoverability of the catalyst. Also, the catalyst was fully characterized by SEM, EDX, FT‐IR, XRD, TGA and TEM analysis.  相似文献   

16.
Constructing a Z-scheme is a significant approach to improve the separation of photogene rated carriers for effective organic pollutant degradation.Herein,a BiVO4/ZnIn2S4(BZ) Z-scheme composite was successfully synthesized,and applied to photodegrade methyl orange(MO) irradiated by a LED lamp.Anchoring the BiVO4 on the ZnIn2S4 nanoparticles promoted the separation of photogenerated electronholes and broadened the light response range.The detailed characterizations,including surface morphology,elements valence state,and photocurrent performance,demonstrated that the enhanced separation of photogenerated carriers was the pivotal reason for the enhanced photocatalysis reaction.Benefiting from the excellent photocatalytic characteristics,the 5% mass ratio of BZ composite presented the highest MO degradation rate of 0.00997 min^-1,which was 1.9 and 10.3 times greater than the virgin ZnIn2S4 and BiVO4,respectively.Furthermore,the BZ hybrid materials indicated a well photo-stability in the four recycling tests.  相似文献   

17.
Metal‐organic framework MIL‐53 (Fe)@C/graphite carbon nitride hybrid (MFeCN), a novel flame retardant, was synthesized by hydrothermal reaction and subsequently added into unsaturated polyester resin (UPR). The structure, morphology, and thermal stability of MFeCN were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), and thermogravimetric analysis (TG). The thermal stability and flammability of the UPR composites were characterized by TG and cone calorimeter tests (CCT). The results of CCT demonstrated that the peak heat release rate (pHRR), total heat release (THR), peak smoke production rate (pSPR), and total smoke production (TSP) of UPR/MFeCN‐4 were reduced by 39.8%, 10.2%, 33.3%, and 14.5%, respectively, comparing with UPR. The results of TG and CCT indicated that MFeCN could improve the thermal stability, flame retardancy, and smoke suppression properties of the UPR composites. The residues after CCT were then characterized by laser Raman spectroscopy (LRS), XPS, and SEM. Finally, based on the above experimental results and analysis, the flame retardancy mechanism of MFeCN was proposed.  相似文献   

18.
A highly porous metal‐organic framework, MIL‐101(Fe), was prepared by a solvothermal method in the presence of amino‐modified Fe3O4@SiO2 nanoparticles, in order to achieve Fe3O4/MIL‐101(Fe) nanocomposite, which was characterized by XRD, FT‐IR, SEM, TEM, BET, and VSM. This hybrid magnetic nanocomposite was employed as heterogeneous catalyst for α‐amino nitriles synthesis through three‐component condensation reaction of aldehydes (ketones), amines, and trimethylsilyl cyanide in EtOH, at room temperature. The recoverability and reusability was admitted for the heterogeneous magnetic catalyst; no significant reduction of catalytic activity was observed even after five consecutive reaction cycles.  相似文献   

19.
Introducing plasmonic metals into semiconductor materials has been proven to be an attractive strategy for enhancing photocatalytic activity in the visible region. In this work, a novel and efficient Ag/Ag2WO4/g‐C3N4 (AACN) ternary plasmonic photocatalyst was successfully synthesized using a facile one‐step in situ hydrothermal method. The composition, structure, morphology and optical absorption properties of AACN were investigated using X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and UV–visible diffuse reflectance spectroscopy, respectively. Photocatalytic performance of AACN was evaluated via rhodamine B and tetracycline degradation. The results indicated that AACN had excellent photocatalytic performance for rhodamine B degradation with a rate constant of 0.0125 min?1, which was higher than those of Ag2WO4 and Ag/Ag2WO4. Characterization and photocatalytic tests showed that the strong coupling effect between the Ag/Ag2WO4 nanoparticles and the exfoliated ultrathin g‐C3N4 nanosheets was superior for visible‐light responsivity and reduced the recombination rate of photogenerated electrons and holes. A proposed mechanism is also discussed according to the band energy structure and the experimental results.  相似文献   

20.
MIL-101(Cr) template method has been employed successfully to synthesize CuCr2O4/CuO composite. The synthesized sample was characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, N2 adsorption–desorption isotherm (BET) analysis, and UV vis- diffuse reflectance spectroscopy (UV-DRS). The photocatalytic efficiency of the nanocomposite was evaluated towards the degradation of methylene blue (MB) dye and antibiotic tetracycline (TC) solution. The morphological studies confirmed that the CuO was uniformly dispersed on the CuCr2O4 matrix. The CuCr2O4/CuO nanocomposite showed high degradation efficiency of about 90% in the presence of H2O2 where the MB degradation reaction got completed in a mere 35 min and ~95% TC got degraded within 120 min.  相似文献   

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