贵金属/WO3复合纳米晶的气敏与光催化研究进展

WO3作为新型的气敏材料和光催化剂具有广阔的应用前景,通过贵金属纳米簇修饰后的WO3复合纳米晶比WO3基体材料在性能上大幅提高。本文综述了贵金属修饰对WO3基体气敏和光催化性能的影响,其中气敏性能以不同敏感气体(如NOx、H2S、H2等)为分类依据,而光催化性能以不同贵金属(Au、Ag、Pt等)添加剂为分类依据,系统综述了贵金属/WO3复合纳米晶的气敏和光催化性能研究最新进展,并总结了常见贵金属/WO3的气敏和光催化机理模型,提出了贵金属/WO3在气敏和光催化应用过程中存在的问题及前景展望。     

基于表面等离子体共振效应的Ag(Au)/半导体纳米复合光催化剂的研究进展

由具有表面等离子体共振(surface plasmon resonance,SPR)效应的贵金属(Ag、Au等)纳米粒子和半导体纳米结构组成的纳米复合光催化剂具有优异的可见光光催化活性,成为新型光催化材料的研究热点之一。本文综述了Ag(Au)/半导体纳米复合光催化剂的制备方法、基本性质以及光催化应用方面的一些重要研究进展;重点介绍了Ag(Au)等纳米粒子的表面等离子共振增强可见光催化活性的机理,以及Ag(Au)纳米粒子与不同类型半导体复合的光催化剂的光催化性能,其中所涉及的半导体包括金属氧化物、硫化物和其他一些半导体;本领域未来几年的研究热点将集中于新型高效的Ag(Au)/半导体纳米复合光催化剂的微结构调控及其用于可见光驱动有机反应的机理研究。本文为基于SPR效应构建Ag(Au)/半导体纳米复合光催化剂的研究提供了有力的参考依据,并且指出Ag(Au)/半导体纳米复合光催化剂的研究是发展可见光高效光催化剂的重要方向。     

Novel in-situ synthesis of Au/SnO2 quantum dots for enhanced visible-light-driven photocatalytic applications

In recent years, visible-light-driven metal–semiconductor nanocomposites have emerged as a suitable material for the decomposition of various water and air pollutants. In this work, a novel plasmonic Au nanoparticle (NP)/SnO₂ quantum dot (SQD) nanocomposite photocatalysts were prepared via a one-step solvothermal technique. The as-prepared plasmonic photocatalysts were characterized by various techniques, and the results established the formation of Au/SQD nanocomposites. The photocatalytic activity of the as-prepared plasmonic Au/SQD nanocomposites was examined by the degradation of Rhodamine B (RhB) at room temperature under visible light, and the Au/SQD photocatalyst, prepared using 1.0?g of tin chloride, exhibited a higher rate constant of RhB degradation than pristine SQDs. This exceptional improvement in catalytic performance under visible light is ascribed to a shift of the band gap from the ultraviolet to the visible region. The surface plasmon resonance effect of Au NPs and the synergistic coupling of the metal and the semiconductor QDs also played a vital role in enhancing the catalytic performance. The process of the photocatalytic degradation of RhB by the Au/SQD nanocomposites under visible light is described.     

WO3/C/Ag3PO4复合材料光催化降解双酚A

以磷酸法制备的活性炭、WO3、AgNO3、Na2HPO4为原料,采用共沉淀法制备WO3/C/Ag3PO4复合材料。采用X 射线衍射（XRD）、傅里叶红外光谱（FT-IR）、光电子能谱（XPS）、扫描电镜（SEM）、透射电镜（TEM）和固体紫外漫反射（UV-DRS）技术对其进行表征。结果表明,Ag3PO4与WO3之间形成异质结。在可见光照射下,以双酚A(BPA)模拟污染物,评价WO3/C/Ag3PO4复合材料的光催化降解性能,并提出 WO3/ C/Ag3PO4 复合材料对BPA的光降解机理。结果表明,在一系列光催化剂中, 23% WO3/ 7% C/ Ag3PO4 复合材料在可见光下对10 mg/L BPA水溶液的降解率在90 min分钟达到95%,明显高于单一的Ag3PO4和WO3。经过3次循环重复,BPA的降解率仍能保持在74%,表明WO3/C/Ag3PO4光催化剂具有良好的稳定性。光催化机理表明,自由基?O- 2和h 在降解过程中起主要作用。     

TiO<Subscript>2</Subscript> porous ceramic/Ag–AgCl composite for enhanced photocatalytic degradation of dyes under visible light irradiation

TiO₂ porous ceramic/Ag–AgCl composite was prepared by incorporating AgCl nanoparticles within the bulk of TiO₂ porous ceramic followed by reducing Ag⁺ in the AgCl particles to Ag⁰ species under visible light irradiation. The porous TiO₂ ceramic was physically robust and chemically durable, and the porous structure facilitated the implantation of AgCl NPs. Compared with the bare TiO₂ ceramic, TiO₂ porous ceramic/Ag–AgCl composite exhibited higher photocatalytic performance for the degradation of MO and RhB under visible light irradiation. The reaction rate constants k of MO and RhB degradation over TiO₂ porous ceramic/Ag–AgCl composite was respectively 6.25 times and 3.62 times higher than those recorded over the bare TiO₂ porous ceramic. The photocatalytic activity showed virtually no decline after four times cyclic experiments under visible light irradiation. Scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectra and X-ray photoelectron spectroscopy were used to characterize the TiO₂ porous ceramic/Ag–AgCl composite.     

Ti(iv) doped WO₃ nanocuboids: fabrication and enhanced visible-light-driven photocatalytic performance

In this paper, we successfully fabricate Ti(iv) doped WO? nanocuboids with controlled Ti(iv) contents through a facile, mild, aqueous-phase route. The characterizations clearly exhibit the optimum amount of the Ti(iv) dopant in under these conditions. The obtained photocatalyst shows excellent visible-light-driven photocatalytic performance. It can decompose an organic dye within 70 min under visible-light irradiation. Such a large activity enhancement probably arises from the change of band structure. The results provide an efficient route for the design of photocatalysts with improved visible-light-driven photocatalytic activity as well as a promising material for use in solar cells, nanodevices, and other applications.     

掺杂型Bi2WO6光催化剂的制备及其光催化性能研究

复合氧化物Bi2WO6可作为一种高效的光催化材料,但Bi2WO6的光生电子空穴对复合率高,分离困难,导致对光的吸收能力下降,光催化效率降低。金属Cu和Ag是良好的光催化剂助剂,能有效降低光催化剂的光生电子空穴对复合率,改善催化剂的光吸收性能。采用水热法制备金属Cu和Ag掺杂的可见光催化剂Bi2WO6,并进行X射线衍射、扫描电子显微镜、紫外-可见光谱和比表面积表征。结果表明,掺杂的金属离子并未进入Bi2WO6晶格内部,只是负载于Bi2WO6表面。掺杂金属后,Bi2WO6的吸收边带变宽,吸光强度变强,比表面积显著增加。以模拟含酚废水为处理对象,考察掺杂型Bi2WO6对苯酚光催化降解效果的影响。实验结果表明,Cu-Bi2WO6光催化剂在光照作用下对苯酚有降解作用,随着光照时间的延长,苯酚的降解程度不断提高,在空气通入量为25 mL·min-1和400 W金卤灯下光照180 min,Cu-Bi2WO6和Ag-Bi2WO6对10 mg·L-1的模拟含酚废水基本降解完成。     

磷钨酸/SiC复合材料的制备及光催化性能研究

以磷钨酸(PTA)和Si C为原料,采用浸渍法制备了4种不同比例PTA的PTA-Si C光催化剂。采用紫外可见漫反射光谱、傅里叶红外变换光谱、X射线衍射光谱、扫描电镜进行表征,并以罗丹明B(Rh B)为降解底物,考察光催化剂的光催化降解性能。结果表明,制备的光催化剂既保持了Si C的载体结构,又保持了PTA的Keggin型结构。PTA的质量分数40%的PTA-Si C光催化降解性能最好,在光照180 min时,Rh B的降解率为66%,光降解反应速率常数为5.21×10^-3min^-1。羟基自由基在光催化降解Rh B中起决定作用的活性物质。     

可见光驱动Ag_3PO_4催化剂的可控制备及活性评价

以AgNO3和Na3PO4、Na2HPO4、NaH2PO4为原料,采用简易液相沉淀法可控制备3种Ag3PO4光催化剂,采用XRD、FE-SEM、UV-Vis、FTIR及BET表征。以罗丹明B为目标污染物,评价样品的可见光催化活性。结果表明,采用Na3PO4、Na2HPO4、NaH2PO4制备Ag3PO4,样品的结晶度逐渐增加,粒径逐渐增大,3种样品均能吸收可见光,去除水体中罗丹明B的反应速率常数分别为0.03,0.10,0.15 min-1。以Na2HPO4为原料可获取高产率、高活性Ag3PO4光催化剂。真实太阳光照射下,Ag3PO4光催化剂可重复利用。单质银的产生降低了催化剂的光催化活性。     

SDBS辅助合成Y2O3/Ag3VO4光催化剂及其催化可见光降解罗丹明B

以V2O5, AgNO3和Y(NO3)3×6H2O为原料、十二烷基苯磺酸钠为辅助剂,采用直接沉淀法和浸渍法制备单斜晶相Ag3VO4和Y2O3/Ag3VO4复合催化剂,表征了产物的结构和形貌,并分析了其形成机理;在可见光下研究了其催化可见光降解罗丹明B(RhB)的性能. 结果表明,所得Y2O3/Ag3VO4复合催化剂吸收边相对纯相Ag3VO4发生红移,禁带宽度减小至1.83 eV,电子-空穴对复合几率降低,对RhB有较好的可见光催化活性和稳定性,可见光照射15 min后,0.08 g 3% Y2O3/Ag3VO4催化200 mL 8 mg/L RhB溶液的降解率达94.2%.     

Fabrication of ternary p-n heterostructures AgCl/Ag2O/NaTaO3 photocatalysts: Enhanced charge separation and photocatalytic properties under visible light irradiation

Ternary p-n heterostructures photocatalysts of AgCl/Ag₂O/NaTaO₃ were synthesized via a simple method and the crystal structure characterized by X-ray diffraction (XRD). The morphology of the photocatalysts were characterized by scanning electron microscopy and transmission electron microscopy. The composition of the photocatalysts was studied by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscope. The photocatalytic activity of the AgCl/Ag₂O/NaTaO₃ photocatalysts was evaluated using the degradation of Rhodamine B. The AgCl/Ag₂O/NaTaO₃ photocatalysts showed higher visible light activity than the pure NaTaO₃ and Ag₂O/NaTaO₃ photocatalysts. Additionally, the photocatalytic mechanism was that the rapidly separation of photoinduced electrons and holes resulted the enhancement of photocatalytic activity.     

Assembling Ag/UiO-66-NH2 Composites for Photocatalytic Dye Degradation

The water pollution currently constitutes a severe threat to our living life, and MOF (metal–organic framework)-based photocatalysts offer an efficient route to clean various water pollutants in an eco-friendly manner. Integration of metal nanoparticles (MNPs) with photoactive MOFs has proven an effective way to further boost the photocatalytic performance. In this work, Ag/UiO-66-NH₂ composites (UiO?=?University of Oslo) have been facilely assembled in two steps involving first wet impregnation of AgNO₃ into UiO-66-NH₂ followed by chemical reduction with NaBH₄. Benefited from the built-in heterostructure that can promote both the electron–hole separation, and the absorption of the visible-light, Ag/UiO-66-NH₂ composites exhibited an enhanced photocatalytic performance than the pristine UiO-66-NH₂ towards photodegradation of RhB (Rhodamine B) dye under the irradiation of UV–Visible light. About 96% of RhB can be degraded by Ag/UiO-66-NH₂ in a period of 40 min. Besides, Ag/UiO-66-NH₂ demonstrated a good recycling stability which showed an only slight drop in the dye photodegradation efficiency after three consecutive runs. The current work suggests that Ag/UiO-66-NH₂ composites have a great potential in practical application toward water remediation.

     

Plasmonic‐enhanced visible‐light‐driven photocatalytic activity of Ag–AgBr synthesized in reactable ionic liquid

BACKGROUND: Plasmonic photocatalysts have attracted considerable attention because of their applications in the degradation of organic pollutants. In order to enhance the stability of AgX photocatalyst, Ag/AgCl, Ag/AgBr/WO₃, and Ag@AgCl/RGO were developed. Results implied that silver halides could maintain stability if the metal Ag was well dispersed on the silver halide particles and could display high catalytic activity. RESULTS: PVP acted as a structure‐directing agent, and a reducing reagent in the reaction. Results show that Ag–AgBr delivered a much higher photocatalytic activity than AgBr and Ag–AgCl. The high photocatalytic activity of the Ag–AgBr composites can be attributed to the presence of metal Ag and the smaller particle size of the samples. The photocatalytic reaction followed first‐order kinetics. The rate constant k for the degradation of MO by Ag–AgBr was 2 and 18 times higher than that of AgBr and Ag–AgCl, respectively. CONCLUSIONS: The MO degradation efficiency of Ag–AgBr was 94% after 10 min. After 5 cycles of repeatability tests, the degradation efficiency of MO still remained at 90%. The high photocatalytic activity of the Ag–AgBr composites can be attributed to the presence of metal Ag and the smaller particle size of the samples. Copyright © 2012 Society of Chemical Industry     

A magnetically separable photocatalyst based on nest-like γ-Fe₂O₃/ZnO double-shelled hollow structures with enhanced photocatalytic activity

Magnetic nest-like γ-Fe(2)O(3)/ZnO double-shelled hollow nanostructures have been successfully synthesized via a multi-step process. The materials have been thoroughly characterized by different techniques. These interesting nest-like hollow nanostructures are composed of ZnO nanoflakes grown on the surface of γ-Fe(2)O(3) hollow spheres. Importantly, these magnetic hollow nanostructures show very high visible-light photocatalytic activity for the degradation of different organic dyes including methylene blue (MB), Rhodamine-B (RhB), and methyl orange (MO). It is further demonstrated that these γ-Fe(2)O(3)/ZnO hybrid photocatalysts are highly stable and can be used repeatedly.     

前驱体对熔盐法合成Bi2WO6光催化剂及其性能的影响

分别以Bi(NO3)3和Na2WO4溶液直接混合所得沉淀、加氨水所得沉淀及Bi(NO3)3×5H2O+Na2WO4×2H2O为前驱体,采用熔盐法合成Bi2WO6光催化剂粉体,研究了不同前驱体所制粉体的物相、形貌,以其为催化剂,在可见光照射下降解罗丹明B溶液. 结果表明,用后二者为前驱体均可得到薄片状纯相Bi2WO6粉体. 加氨水所得沉淀为前驱体所制Bi2WO6粉体的光催化性能最好,在可见光照射下对0.01 mmol/L RhB溶液的降解率在60 min内达99%.     

具有高效可见光活性的AgCl/AgVO_3异质结光催化剂的原位合成

以水热法合成的AgVO_3为前驱体,在其表面通过原位离子交换法合成AgCl/AgVO_3异质结光催化剂,利用XRD、SEM和UV-Vis等对其结构、形貌和光吸收性能进行表征,并以酸性橙-Ⅱ模拟环境中染料污染物,考察了AgCl/AgVO_3异质结的可见光催化性能。结果表明,AgCl/AgVO_3异质结光催化剂具有高效的可见光催化活性,在可见光照射下15 min,酸性橙-Ⅱ降解率达到80%,循环使用4次后,降解率仍能保持60%。自由基捕获实验结果表明,h~+和·O_2~-为光催化反应中的主要活性物种。光催化性能的提高主要归因于AgCl/AgVO_3异质结构的形成,这利于光生电子-空穴对转移和分离。最后探讨了增强AgCl/AgVO_3光催化性能的可能机理。     

Growth and optical properties of hierarchical flower-like ZnO nanostructures

The integration of low dimensions nanoscale building blocks into 3D architectures has attracted great scientific attention. We have obtained the novel hierarchical flower-like ZnO nanostructures self-assembled by nanorods via a facile hydrothermal method. The as-synthesized samples were characterized with various technologies. The field emission scanning electron microscope (FESEM) images indicated that hydroxide ions play a significant role on the formation of hierarchical flower-like ZnO nanostructures. The X-ray diffraction (XRD) result proved that the nanocrystals were well crystallized hexagonal wurtzite structure. A possible growth mechanism of the nanostructures was proposed based on the effects of hydroxide ions. And the TEM imagines provided some important evidence for the proposed growth mechanism. UV–vis adsorption and photoluminescence (PL) spectra results indicated that the obtained ZnO nanostructurs have a good optical-absorption and photoluminescence property. The as-synthesized ZnO nanostructures exhibited superior photocatalytic performance, which was higher than that of commercially available ZnO.     

Enhanced visible light photocatalytic performance of Sb-doped (BiO)2CO3 nanoplates

Sb-doped (BiO)₂CO₃ nanoplates have been successfully fabricated via a facile hydrothermal method. XRD patterns, XPS spectra, SEM and TEM images demonstrated that doping with antimony (Sb) has no effect on the crystal phase, morphology and structure of (BiO)₂CO₃ nanoplates. However, the red shift of diffraction peak in the 2θ range of 29–32° was observed, which could be attributed to the substitution of larger radius of Bi atoms by lower radius of Sb atoms resulting in the decrease of lattice parameters. The photocatalytic performance of Sb-doped (BiO)₂CO₃ nanoplates was evaluated by the degradation of RhB upon visible light irradiation. It was found that the visible-light-induced photocatalytic activity of Sb-doped (BiO)₂CO₃ nanoplates was significantly improved, which was mainly attributed to its enhanced surface area and electron transfer rate. It was proposed that RhB photodegradation proceeded through a photosensitization pathway upon visible light irradiation.     

Ag/AgCl coated polyacrylonitrile nanofiber membranes: Synthesis and photocatalytic properties

A membrane based photocatalyst consisting of Ag/AgCl coated PAN nanofibers was synthesized in large quantities by electrospinning technique combining electroless plating method and subsequent in situ oxidation strategy. Electrospinning was firstly used to fabricate PAN/AgNO₃ composite nanofibers. After reduction, Ag nanoparticles dispersed along the nanofibers act as seeds in the following metal electroless plating step for the growth of continuous Ag shell. Then an in situ oxidation reaction between Ag shells and FeCl₃ solution was carried on to prepare Ag/AgCl coated PAN nanofiber membranes. The as-prepared materials exhibited excellent photocatalytic activity under visible-light, long-term stability, flexibility, as well as easy separation from the liquid. The present work can open a new and effective route for preparing high-performance membrane based photocatalysts for practical application.     

pH dependent morphology and texture evolution of ZnO nanoparticles fabricated by microwave-assisted chemical synthesis and their photocatalytic dye degradation activities

ZnO nanostructures are well-known photocatalysts for the degradation of toxic organic dyes and their morphology, size, and other physicochemical properties play important roles in their photocatalytic performance. To study the effect of size, morphology, and synthesis conditions in photocatalytic performance, we synthesized ZnO nanoparticles of different morphologies through a simple microwave-assisted chemical process at different pH values of the reaction mixture. Different pH values of the reaction mixture produced ZnO nanoparticles of different morphologies and sizes. The nature of the pH controlling agent and final pH of the reaction mixture were seen to have considerable effects on the lattice parameters and microstrain of the ZnO nanocrystals, along with their photocatalytic performance. We observed that while the ZnO nanostructures synthesized at very high pH values of the reaction mixture have a high specific surface area, their photocatalytic activity is higher when they are synthesized at acidic pH or pH near the isoelectric point of ZnO. The results demonstrate that the photocatalytic activity of ZnO nanostructures not only depends on their size or specific surface area but also strongly depends on the concentration of catalytic sites at their surface.