新型光催化剂钨酸锌的制备及性能改性研究进展

当今世界,全球能源危机和环境污染问题日趋紧迫,严重危害人类健康并制约着人类社会发展。为了人类可持续发展,迫切需要开发和应用清洁无污染的新能源来解决环境问题。近年来,光催化氧化技术因其室温深度反应以及可直接利用太阳能作为光源来驱动反应等特点,成为一种高效、理想的环境污染治理技术,引起了各国研究者的密切关注,开发和应用高效的光催化剂已成为环境领域的研究热点。过去几十年,二氧化钛(TiO_2)因无毒、廉价易得、稳定性好等特点,成为研究最广的半导体光催化剂。然而,较窄的光频率响应范围、低的太阳能利用率等缺点限制了其实用化进程。为此,研究人员采用各种不同的制备方法,研究开发了大量具有不同结构的非TiO_2基光催化材料,包括简单氧化物、复合金属氧化物、钙钛矿型复合氧化物等。其中,钨酸锌(ZnWO_4)是一种具有宽禁带、高激发能、高紫外光响应、高催化活性等独特物理化学特性的重要新型非TiO_2基半导体光催化剂,被认为是最有潜力的金属钨酸盐光催化剂之一,其纳米粉体的制备合成及性能研究可为可见光催化降解有机污染物开辟一条新的路径,具有极其重要的研究价值,也是近些年来新型光催化剂研究的焦点。ZnWO_4半导体光催化剂的晶体形貌、尺寸、组成、掺杂物等对其光催化活性具有重要影响。目前,研究者们已通过固相反应法、水热法、溶剂热法、溶胶-凝胶法、化学沉淀法、微乳液法、模板法等不同的制备方法合成了具有不同形貌、尺寸和结晶度的ZnWO_4纳米光催化剂,探讨了制备工艺、晶体特性(形貌、尺寸、组成、结晶程度等)、光催化性能之间的关系。但这些方法合成的ZnWO_4光响应区域仍然较窄,只能吸收太阳光谱中具有较高能量的紫外光,其光量子产率仍然较低。为了进一步提高ZnWO_4的光响应范围,科学家们采用掺杂改性和材料复合等多种活性改进方法来提高其光电转换效率、拓宽光波吸收范围,使其具有良好的可见光响应,优化了其光催化性能。因此,加深制备工艺和性能改性方法对ZnWO_4晶体形貌、尺寸、组成等特性影响以及这些特性对光催化活性影响的理解,对进一步推进钨酸盐光催化材料的研究和应用具有重要的科学意义和实用价值。基于此,本文在分析ZnWO_4晶体结构特点的基础上,主要从制备方法、掺杂改性和材料复合这三个方面综述了近年来ZnWO_4光催化剂的研究进展,探讨了其结构、形貌、性能之间的相互关系,并进一步指出了ZnWO_4光催化剂的发展前景及提高其光催化性能的主要措施。     

贵金属改性TiO2光催化剂的机理及研究进展

利用贵金属改性TiO2光催化剂是提高TiO2光催化活性的主要方法之一,在离子掺杂改性TiO2研究中受到重点关注。综述了贵金属改性TiO2光催化剂的机理,总结了贵金属改性TiO2光催化剂的主要制备方法,分析了目前贵金属改性TiO2光催化剂研究中存在的问题,指出通过某些贵金属掺杂TiO2光催化剂能克服贵金属表面沉积改性方法的不足,并能有效改善TiO2光催化剂的光催化性能。     

不同形貌Ag修饰TiO_2的制备及其光催化性能研究进展

TiO_2凭借其优越的光催化性能,在环境治理方面得到了广泛应用。为了增加纯TiO_2的可见光利用率以及提高其量子效率,Ag修饰TiO_2得到了广泛的研究。根据光催化剂形貌分类,综述了近年来Ag修饰TiO_2微粒、薄膜、纳米管、纳米线的制备工艺以及光催化性能研究,并展望了Ag改性后的TiO_2应用前景。     

铁酸锌在特性材料方面的研究与展望

铁酸锌具有尖晶石型微观晶体结构特点,化学键牢固,原子堆积紧密,在锌冶金工业中用物理和化学方法均难以处理。铁酸锌的这种特殊结构使得其具有许多优良的性能如气敏特性、光催化活性、化学稳定性及铁磁特性。对近几年来国内外对铁酸锌在材料特性、用途、实验室制备方法等方面的研究状况进行综述,对其在不破坏晶体结构的条件下从工业废渣中分离以达到工业化生产的可行性进行探究,拟定解决关键科学问题的实验探究方向。     

Cu掺杂FeVO4光催化剂的制备及其光催化性能

为进一步提高钒酸铁(FeVO4)光催化活性,采用液相沉淀法分别制备钒酸铁和钒酸铜前躯体,再将钒酸铁和钒酸铜前驱体混合后进行热处理,制备了铜掺杂钒酸铁光催化剂,并采用X射线衍射(XRD)、扫描电子显微镜(SEM)、表面积(BET)和X射线光电子能谱分析(XPS)对样品进行表征和分析.在可见光照射下,通过光催化降解甲基橙溶液评价Cu掺杂对FeVO4光催化剂活的影响.结果表明,Cu/FeVO4光催化剂为三斜型,当掺杂质量分数大于5%时,晶体中出现新相Cu3Fe4(VO4)6;掺杂后样品的表面形貌产生了变化,但其比表面积变化较小;Cu/FeVO4样品的光催化活性大幅提高,主要是由于FeVO4和新相间起到类似复合半导体的作用;在所进行实验的条件下,钒酸铜的最佳掺杂质量分数为5%时,掺杂后的FeVO4对甲基橙溶液的脱色率较未掺杂前提高30%左右.     

新型可见光催化剂BiVO4的制备方法

作为一种新型可见光催化剂,钒酸铋（BiVO₄）因为拥有较窄的禁带宽度（2.4eV）以及合适的导带和价带位置在可见光催化领域受到广泛关注,在水的光解以及有机污染物的降解等方面都有研究及应用。不同的制备方法对材料的形貌和结构都有较大的影响,进而影响到光催化剂的光催化性能。综述了国内外BiVO₄的制备方法,并在此基础上展望了该领域的发展方向。     

AgCl/BiOCl 片组装纳米花球的合成及光催化性能研究

以硝酸铋(Bi(NO_3)_3·5H_2O)、硝酸银(AgNO_3)、氯化钾(KCl)为原料,通过无模板、无加热、无表面活性剂的绿色化学方法制备了BiOCl片组装纳米花球,并在它的基础上采用浸渍法负载AgCl实现了对它的改性。以罗丹明B(RhB)和甲基橙(MO)为光催化反应降解模型,进行了光催化活性测试,考察了不同浸渍次数的AgCl对BiOCl光催化剂反应活性和稳定性的影响。用XRD、SEM、EDS、UV-Vis吸收光谱等手段对其结构、形貌、光谱吸收性能等进行了表征。研究表明,AgCl改性的BiOCl复合光催化剂的光催化性能明显优于纯BiOCl,当浸渍2遍时,光催化降解RhB活性最佳,当浸渍5遍时,光催化降解MO活性最佳。     

卤氧化铋异质结型可见光光催化剂的新进展

卤氧化铋BiOX (X=Cl,Br,I)以其特殊的层状结构和合适的禁带宽度显示出了优异的光催化性能,特别是BiOBr和BiOI可以直接作为可见光光催化剂,引起了人们的广泛关注.围绕这两种化合物为中心的异质结型可见光光催化剂具有制备简单、光生载流子分离效率较高和可见光活性普遍较强的特点.主要综述了BiOBr和BiOI两种材料的异质结型可见光光催化剂的制备方法及形貌,以及光催化活性和机理的最新研究进展,并展望了其发展趋势.     

氧化锌/氧化镁纳米复合材料的制备及其光催化性能研究

采用微波辅助共沉淀法制备了纳米氧化锌/氧化镁(ZnO/MgO)光催化剂,并对催化剂样品进行了X射线衍射、透射电镜、红外光谱以及紫外-可见吸收光谱等表征。以亚甲基蓝(MB)为目标降解物对不同锌镁比的ZnO/MgO催化剂样品及相同方法下合成的ZnO及MgO进行光催化降解实验。结果表明:合成的纳米ZnO/MgO光催化剂由立方相的ZnO和非晶相的MgO组成,其尺寸均匀,在40nm左右,并在紫外区域吸收性能良好。光催化降解MB实验表明,锌镁比为2∶1时ZnO/MgO催化剂的光催化性能最佳。     

活性炭负载TiO2光催化材料的研究

活性炭(AC)及活性炭纤维(ACF)作为光催化剂载体具有较高的比表面积和较强的吸附性能,可以有效提高负载型光催化剂TiO2/AC和TiO2/ACF对有机污染物的光催化降解效率.首先介绍了TiO2光催化剂的结构特性以及各种掺杂改性方法,对负载型TiO2/AC及TiO2/ACF光催化剂的各种制备方法进行了详细评述.在此基础上,讨论了影响有机污染物光催化降解性能的重要因素,指出了负载型TiO2光催化材料研究中有待解决的问题和发展方向.     

Atomic engineering of mixed ferrite and core-shell nanoparticles

Nanoparticulate ferrites such as manganese zinc ferrite and nickel zinc ferrite hold great promise for advanced applications in power electronics. The use of these materials in current applications requires fine control over the nanoparticle size as well as size distribution to maximize their packing density. While there are several techniques for the synthesis of ferrite nanoparticles, reverse micelle techniques provide the greatest flexibility and control over size, crystallinity, and magnetic properties. Recipes for the synthesis of manganese zinc ferrite, nickel zinc ferrite, and an enhanced ferrite are presented along with analysis of the crystalline and magnetic properties. Comparisons are made on the quality of nanoparticles produced using different surfactant systems. The importance of various reaction conditions is explored with a discussion on the corresponding effects on the magnetic properties, particle morphology, stoichiometry, crystallinity, and phase purity.     

Different methods in TiO2 photodegradation mechanism studies: gaseous and TiO2-adsorbed phases

The development of photocatalysis processes offers a significant number of perspectives especially in gaseous phase depollution. It is proved that the photo-oxidizing properties of photocatalyst (TiO(2)) activated by UV plays an important role in the degradation of volatile organic compounds (VOC). Heterogeneous photocatalysis is based on the absorption of UV radiations by TiO(2). This phenomenon leads to the degradation and the oxidation of the compounds, according to a mechanism that associates the pollutant's adsorption on the photocatalyst and radical degradation reactions. The main objective of the study is the understanding of the TiO(2)-photocatalysis phenomenon including gaseous and adsorbed phase mechanisms. Results obtained with three different apparatus are compared; gaseous phases are analysed and mechanisms at the gaseous phase/photocatalyst interface are identified. This study leads to improve understanding of various mechanisms during pollutant photodegradation: adsorption of pollutants on TiO(2) first takes place, then desorption and/or photodegradation, and finally, desorption of degradation products on TiO(2). The association of analytical methods and different processes makes the determination of all parameters that affect the photocatalytic process possible. Mastering these parameters is fundamental for the design and construction of industrial size reactors that aim to purify the atmosphere.     

纳米光催化材料形态控制及应用

高效纳米光催化材料制备和应用技术开发是实现光催化技术实用化的关键。本文综述了多种纳米光催化材料形态控制技术及部分材料应用技术，展望了该领域的发展前景。     

水热法制备TiO2纳米棒阵列及应用研究进展

TiO_2纳米棒阵列由于具有电子传输率高和光散射效应强等优异的特性,从而在太阳能电池、光催化、光解水制氢等领域中具有广阔的应用前景。主要从水热法制备工艺及生长机理、形貌优化及改性和应用几个方面综述了TiO_2纳米棒阵列的研究进展,并对今后的研究趋势进行展望。     

类水滑石制备及其功能改性的研究进展

目的 为了探索类水滑石的低成本制备方法及插层改性增加其新功能的方法,提出类水滑石制备及其功能改性的环保新方向。方法 基于类水滑石的常规制备方法以及矿物原料和固废制备类水滑石的方法,综述类水滑石常规制备方法的优缺点,同时综述增强阻燃性能、吸附性能、催化性能、润滑性能、光催化、抗菌抗肿瘤、抗紫外线等性能的类水滑石的功能改性方法。结论 认为目前类水滑石制备及改性应加强2个方面的研究：利用矿物原料和钢渣、矿渣、粉煤灰等固体废弃物直接制备类水滑石,以降低其制备成本;利用水滑石和类水滑石的层状结构,以及层间阴离子的可交换的特性,加强其多种性能的改性。     

Controllable synthesis of SnO2 photocatalyst with superior photocatalytic activity for the degradation of methylene blue dye solution

SnO₂ photocatalyst was successfully synthesised by novel chemical route in hydrothermal environment and annealed at two different temperatures viz 550 and 600 °C, respectively. The crystal structure, optical properties, surface and bulk morphology have been characterised using various tools like X-ray diffraction (XRD), UV visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscope (TEM) and scanning electron microscope (SEM). Cubic, spheres and porous like morphology of SnO₂ photocatalyst was successfully confirmed using SEM micrographs and TEM. In addition to this the photocatalytic activity was evaluated towards the degradation of methylene blue dye solution. SnO₂ photocatalyst annealed at 600 °C exhibits excellent photocatalytic efficiency which may be attributed to the unique morphology, high crystalline nature and charge separation. The photocatalyst efficiency was further tested towards the concentration of dye, catalyst dosage and pH of the dye. The involvement of ?OH in the photocatalytic reaction was evidenced using trapping experiment by employing different scavengers. The photocatalyst was moderately active, stable upto its fifth usage and stability of the photocatalyst before and after the photocatalytic reaction was also been studied using XRD and SEM.     

Tailoring magnetic and dielectric properties of rubber ferrite composites containing mixed ferrites

Rubber ferrite composites containing various mixed ferrites were prepared for different compositions and various loadings. The magnetic and dielectric properties of the fillers as well as the ferrite filled matrixes were evaluated separately. The results are correlated. Simple equations are proposed to predetermine the magnetic and dielectric properties. The validity of these equations is verified and they are found to be in good agreement. These equations are useful in tailoring the magnetic and dielectric properties of these composites with predetermined properties.     

Nanosized bismuth ferrite powder prepared through sonochemical and microemulsion techniques

Two processing routes, namely sonochemical and microemulsion have been exploited to prepare bismuth ferrite powders. Phase pure nanosized BiFeO₃ powders are prepared by sonochemical and microemulsion techniques in the temperature range of 400 °C and at 500 °C which is much lower than that of the conventional preparation methods. The XRD obtained from both cases was likely to be pure bismuth ferrite. Though the microemulsion based powders showed slightly better properties with respect to particle size, surface area, and final density, sonochemically prepared powders may be more acceptable considering the ease of preparation and cost effectiveness.     

Synthesis and characterization of zinc ferrite nanoparticles obtained by self-propagating low-temperature combustion method

The self-propagating low-temperature combustion method was used to produce nanocrystalline particles of zinc ferrite. The products were characterized for chemical and phase composition, morphology and magnetic properties. The results obtained showed the formation of single-phase zinc ferrite nanoparticles with an average particle size of about 40 nm. As-synthesized powder displayed good magnetic property. Due to the simplicity and low cost of this process, it could also become a valuable starting point for the generation of other mixed and complex ferrites.