BiO3对染料的光催化降解性能

近年来 ,利用半导体材料光催化降解有害污染物已成为比较热门的研究课题之一 [1,2 ] ,因其能有效地利用太阳能并在反应中产生强氧化能力的空穴和羟基自由基 ,因而备受人们的关注 .目前使用较多的是催化活性高 ,稳定性好的 Ti O2 [3] ,但由于其带隙较宽 ( 3.2 e V) ,只能吸收波长 λ≤ 387nm的紫外光 .因此研制新型光催化剂或改善催化效率仍是重要研究课题 .近年来 ,有报道用 Bi2 O3光催化处理含亚硝酸盐废水的实验研究 [4 ] ,结果比较满意 .本研究对 Bi2 O3的制备、表征及其作光催化剂处理各种染料溶液进行实验 ,结果表明 ,Bi2 O3具有较…     

纤维状TiO2／Bi2O3光催化剂的制备及其光催化性能

研究了SrCo0．7Fe0．2Mo0．103-δ（SCFM）材料的相组成、微观结构、热膨胀系数、氧渗透性能和化学稳定性,其结果和文献中的SrCo0．8Fe0.2O3-δ（SCF）做了对比．通过EDTA-citric混合方法成功获得了纯相SCFM材料．SCFM材料在500-1050℃显示出比SCF材料更低的热膨胀系数（24×10^-6-29×10^-6／K）,表明其具有一种更稳定的结构,尽管由于Mo掺杂造成其透氧率比SCF材料低,但是SCFM的透氧率仍然维持在一个较高水平．证实SCF中的Mo掺杂能够阻止晶格中的有序-无序转变,提高了其在CO2下的化学稳定性．     

TiO2纳米粒子制备方法对其光催化活性的影响

分别用胶溶法、金属醇盐水解法和低温水解法制备了TiO2纳米粒子;采用XRD和BET技术,测试了TiO2粒子的粒径、晶型及表面积。以庚烷的气相光催化氧化为探针反应,考察了不同方法、不同温度处理的TiO2粒子的光催化活性。结果表明,以胶溶法和金属醇盐水解法制备的TiO2粒子,随焙烧温度的增加TiO2粒子长大,晶型由锐钛矿向金红石型转变,光催化活性降低。用低温水解法,可在低温下制得金红石型TiO2粒子,但其催化活性很低。说明由原料和制备方法所决定的TiO2粒子的物理化学性质,影响其光催化行为。锐钛矿型TiO2粒子催化活性较金红石型TiO2好。这是由于前者的表面羟基含量较高且带隙能较大的缘故。     

铕掺杂对纳米TiO2的光催化活性的影响

用溶胶-凝胶法制备了掺杂Eu3+的纳米TiO2,用XRD和TG-DTA对其进行了表征,并以正庚烷为气相有机污染物的实例研究了样品的光催化活性,发现Eu3+进入TiO2晶格中引起了TiO2晶格膨胀,导致晶格畸变增大,抑制了TiO2晶相的转变和粒径的增长.结果表明,Eu3+掺杂可提高TiO2的光催化活性,并且当掺杂摩尔分数为0.3%时,光催化活性最好.随着焙烧温度的升高,光催化活性下降,而利用较高的水解酸度则有利于得到光催化活性较高的样品.     

Tunable Synthesis of Core-shell α-Fe2O3/TiO2 Composite Nanoparticles and Their Visible-light Photocatalytic Activity

Uniform α-Fe₂O₃/amorphous TiO₂ core-shell nanocomposites were prepared via a hydrolysis method and α-Fe₂O₃/anatase TiO₂ core-shell nanocomposites were obtained via a post-calcination process. The structure and morphology of the products were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and scanning electron microscopy. Amorphous TiO₂ nanoparticles with diameters of ten to several tens nanometer were formed on the surface of α-Fe₂O₃ nanoparticles and the coverage density of the secondary TiO₂ nanoparticles in the composite can be controlled by varying the concentration of Ti(BuO)₄ in the ethanol solution. The visible-light photocatalytic properties of different products towards Rhodamine B(RhB) were investigated. The results show that the α-Fe₂O₃/amorphous TiO₂ exhibits a good photocatalytic property owing to the extension of the light response range to visible light and the efficient separation of photogenerated electrons and holes between α-Fe₂O₃ and amorphous TiO₂.     

Cu2+掺杂的Bi2O3的制备及光催化性能的研究

本文采用并流沉淀法制备了Cu2+掺杂的纳米Bi2O3光催化剂(Cu/Bi原子比分别为1%,2%,3%和4%)。以甲基橙模拟有机污染物对催化剂的光催化性能进行了考察。用比表面(BET)、X-射线粉末衍射(XRD)、X-射线光电子能谱(XPS),紫外-可见漫反射光谱(DRS)和表面光电压谱(SPS)对所制备的催化剂进行了表征。结果表明,Cu2+掺杂量为3%时制备的Bi2O3具有最高的比表面积、孔容、最小孔径和晶粒尺寸。对甲基橙的光催化脱色结果显示掺杂量为3%时Cu2+-Bi2O3表现出最佳的光催化活性。     

Preparation and Photocatalytic Activity of Ce,H3PW12O40 co-doped TiO2 Hollow Fibers

A series of Ce, H3PW12O40 co-doped TiO2 hollow fibers photocatalysts have been prepared by sol-gel method using ammonium ceric nitrate, H3PW12O40 and tetrabutyltitanate as precursors and cotton fibers as template, followed by calcination at 500 ℃ in N2 atmosphere for 2 h. Scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption mea- surements, and UV-Vis spectroscopy are employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The photo- catalytic performance of the samples has been studied by photodegradation phenol in water under UV and visible light irradiation. The results show that the TiO2 fiber materials have hollow structures, and the co-doped TiO2 hollow fibers exhibit higher photocatalytic activities for the degradation of phenol than un-doped, single-doped TiO2 hollow fibers under UV and visible light. In addition, the recyclability of co-doped TiO2 fibers is also confirmed that the TiO2 fiber retains ca. 90% of its activity after being used four times. It is shown that the co-doped TiO2 fibers can be activated by visible light and may be potentially applied to the treatment of water contaminated by organic pollutants. The synergistic effect of Ce and H3PW12O40 co-doping plays an important role in improving the photocatalytic activity.     

沉淀法制备Bi2O3的晶相转变过程及其光催化性能

以硝酸铋为原料,氨水为沉淀剂,通过液相沉淀法制得前驱体Bi(OH)₃,并将Bi(OH)₃分别在不同温度和时间下焙烧。利用X射线衍射(XRD)、拉曼光谱、热重(TG)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-Vis DRS)详细研究了Bi(OH)₃转变为Bi₂O₃的过程及相变过程中粒子形貌、大小、光吸收性质等。结果表明,前驱体Bi(OH)₃经过焙烧之后,发生了如下的转变过程:Bi(OH)₃→Bi₅O₇NO₃→β-Bi₂O₃/Bi₅O₇NO₃→β-Bi₂O₃/Bi₅O₇NO₃/α-Bi₂O₃→α-Bi₂O₃,而且转变过程伴随着粒子长大。在上述转变过程中,与Bi₅O₇NO₃向β-Bi₂O₃转变的过程相比,从β-Bi₂O₃到α-Bi₂O₃相变过程更为迅速。此外,以光催化降解罗丹明B(RhB)为模型反应,考察了不同晶相的Bi₂O₃光催化活性,结果表明Bi₅O₇NO₃和β-Bi₂O₃材料具有优异的光催化性能,而α-Bi₂O₃具有较低的光催化活性。     

制备方法对Nd_2O_3上过氧物种光诱导生成的影响

分别采用水解、水热和燃烧法制备了三种主要物相均为立方Nd_2O_3的样品。以325 nm激光为激发源,在室温和空气气氛下对上述样品上过氧物种的光诱导生成情况进行了比较考察。经Raman光谱仪的激光束照射后,三种样品上均可检测到过氧物种的生成,但燃烧法制备的样品上过氧的生成速率显著大于其他两种样品。O_2-和CO_2-TPD(程序升温脱附)的表征结果表明,与水解和水热法制备的立方Nd_2O_3相比,燃烧法制备的样品表面含有更多的低配位晶格氧物种,晶格氧的碱性也更强,因而更有利于在光诱导下与分子氧反应生成过氧物种。     

TiO2/Bi2O3纳米复合体的制备及可见光催化产氢性能

首先采用相分离的水解-溶剂热法制备了Bi₂O₃纳米粒子,然后利用简单的湿化学法在Bi₂O₃表面负载不同比例的TiO₂纳米颗粒,进而得到TiO₂/Bi₂O₃纳米复合体。通过气氛调控的表面光电压谱(SPS)等测试表明,表面负载适量的TiO₂后能够提高Bi₂O₃光生电荷分离。可见光催化产氢和降解污染物测试结果进一步证明,表面负载适量的TiO₂后可显著提高其可见光催化活性,其中Ti/Bi摩尔比为7%时具有最高的光催化活性。这主要归因于TiO₂具有较为合适的导带能级位置,可以接收Bi₂O₃在可见光激发下所产生的高能级电子,从而抑制光生电子-空穴对复合,并且维持了高能级电子较高的还原能力。     

光催化纳米材料的制备与光催化活性

光催化材料作为催化剂能催化降解数千种有毒有害化合物,它条件温和、无毒无害、无二次污染,是非常有发展前途的环保方法。但该法也有缺陷,如需要紫外光照射、对高浓度污染物降解能力差等。本文综述了光催化纳米材料的制备方法,并对提高光催化剂催化活性的修饰方法进行了评述,对光催化材料制备及修饰的发展方向和趋势进行了展望。     

Lu2O3∶Bi3+粉末晶体发光性能的研究

采用共沉淀法和燃烧法分别制备得到纳米和亚微米的Lu2O3∶Bi^3＋的粉末晶体。立方结构,属Ia3^-[206]空间群,晶格常数a=1.039 nm,密度高达9.4 g·cm^-3。利用XRD,TEM,荧光光谱和阴极射线发光等方法,研究了不同的制备方法和条件对制成样品的结构、形貌、发光亮度、光谱以及余辉的影响。两种方法制得的样品在紫外和阴极射线激发下,有亮度较高的兰青色的发光。余辉较短,衰减曲线是单指数型。     

高催化活性2D/2D Ti3C2/Bi4O5Br2纳米片异质结的构建及其可见光催化去除NO

This study concentrated on the production of a two-dimensional and two-dimensional (2D/2D) Ti₃C₂/Bi₄O₅Br₂ heterojunction with a large interface that applied as one of the novel visible-light-induced photocatalyst via the hydrothermal method. The obtained photocatalysts enhanced the photocatalytic efficiency of the NO removal. The crystal structure and chemical state of the composites were characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that Ti₃C₂, Bi₄O₅Br₂, and Ti₃C₂/Bi₄O₅Br₂ were successfully synthesized. The experimental results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the prepared samples had a 2D/2D nanosheet structure and large contact area. This structure facilitated the transfer of electrons and holes. The solar light absorptions of the samples were evaluated using the UV-Vis diffuse reflectance spectra (UV-Vis DRS). It was found that the absorption band of Ti₃C₂/Bi₄O₅Br₂ was wider than that of Bi₄O₅Br₂. This represents the electrons in the Ti₃C₂/Bi₄O₅Br₂ nanosheet composites were more likely to be excited. The photocatalytic experiments showed that the 2D/2D Ti₃C₂/Bi₄O₅Br₂ composite with high photocatalytic activity and stability. The photocatalytic efficiency of pure Bi₄O₅Br₂ for the NO removal was 30.5%, while for the 15%Ti₃C₂/Bi₄O₅Br₂ it was 57.6%. Moreover, the catalytic reaction happened in a short period. The concentration of NO decreased exponentially in the first 5 min, which approximately reached the final value. Furthermore, the stability of 15%Ti₃C₂/Bi₄O₅Br₂ was favorable: the catalytic rate was approximately 50.0% after five cycles of cyclic catalysis. Finally, the scavenger experiments, electron spin resonance spectroscopy (ESR), transient photocurrent response, and surface photovoltage spectrum (SPS) were applied to analyze the photocatalytic mechanism of the composite. The results indicated that the 2D/2D heterojunction Ti₃C₂/Bi₄O₅Br₂ improved the separation rate of the electrons and holes, thus enhancing the photocatalytic efficiency. In the photocatalytic reactions, the photogenerated electrons (e⁻) and superoxide radical (·O₂⁻) were critical active groups that had a significant role in the oxidative removal of NO. The in situ Fourier-transform infrared spectroscopy (in situ FTIR) showed that the photo-oxidation products were mainly NO₂⁻ and NO₃⁻. Based on the above experimental results, a possible photocatalytic mechanism was proposed. The electrons in Bi₄O₅Br₂ were excited by visible light. They jumped from the valence band (VB) of Bi₄O₅Br₂ to the conduction band (CB). Then, the photoelectrons transferred from the CB of Bi₄O₅Br₂ to the Ti₃C₂ surface, which significantly promoted the separation of the electron-hole pairs. Therefore, the photocatalytic efficiency of Ti₃C₂/Bi₄O₅Br₂ on NO was significantly improved. This study provided an effective method for preparing 2D/2D Ti₃C₂/Bi₄O₅Br₂ nanocomposites for the photocatalytic degradation of environmental pollutants, which has great potential in solving energy stress and environmental pollution.     

MnOx／Al2O、MnOx／BaO—Al2O3催化剂的制备、表征及其对甲烷低温燃烧的催化活性

改变锰的负载最及前驱体,制备了MnOx/Al2O、MnOx/BaO-Al2O3系列催化剂;采用X-射线衍射（XRD）、程序升温还原（TPR）对催化剂进行表征,并考察了BaO的加入对CH4低温燃烧催化活性的影响。结果表明,用醋酸锰作前驱体与用硝酸锰制备的催化剂相比,其活性组分分散性好、氧中心活性高,催化CH4低温燃烧的活性高。在Al2O3载体中掺入BaO,催化剂的氧中心数目的没有明显变化,但氧中心活性有所下降,因而降低了对CH4低湿燃烧的催化活性。     

Preparation and Photocatalytic Activity of TiO2 Films on Silica Glass Substrates by Assembly Technique

Nanostructured TiO₂ coating films on silica glass substrates were prepared by the assembly technique. TiO₂ colloids were synthesized employing the sol‐gel method using TiCl₄ as a precursor. The effect on the surface structures which was caused by the polyethylene glycol (PEG) added to the precursor solution and the photocatalytic activity were studied. The experimental results showed that the cobble‐like TiO₂ coating films were synthesized at 500 °C. On the surface of the samples, TiO₂ films exhibited uniform shape and a narrow size distribution. The result of proper PEG added to the precursor solution led to the decreasing of the size of TiO₂ particles and the increasing of the surface area of the samples. The photocatalytic activity of TiO₂ films with PEG was higher than that of samples without PEG.     

水热法制备Bi2O3纳米片及其电化学性能的研究

以Bi(NO₃)₃和氨水为原料、水溶性淀粉为分散剂, 采用水热法制备了Bi₂O₃纳米片, 用X射线衍射(XRD)、扫描电子显微技术(SEM)和氮气吸附-脱附等对材料进行了表征. 结果表明Bi₂O₃纳米片厚度分布比较窄, 比表面积达到9.26 m²/g. 同时, 采用循环伏安法和充放电仪测试了Bi₂O₃纳米片的电化学性能, 结果显示其具有一定的电化学活性.     

Ce_2Mo_3O_(12)超微粒子的制备及催化性能

以硝酸铈和钼酸铵为原料 ,采用溶胶 -凝胶法和微波加热技术制备了Ce2 Mo3 O12 超微粒子催化剂 ,使用DTA -TG ,IR ,XRD以及BET比表面测试等表征手段 ,考察了制备条件对复合氧化物超微粒子形成 ,晶相和比表面积的影响 .同时 ,测试了该样品对甲苯选择性氧化制苯甲醛反应的催化性能 .结果表明 :制备Ce2 Mo3 O12 超微粒子的适宜条件为 :初始溶液pH =1.0 ,柠檬酸 / (铈 +钼 )摩尔比等于 0 .4 ,在此条件下制得的干凝胶 ,经微波加热处理后 ,粒子的比表面积为 35 .8m2 /g ,粒径约为 4 0nm .在由甲苯气相选择氧化制苯甲醛的反应中表现出较好的催化活性     

NO在Er2O3/Bi2O3催化剂上的程序升温分解

NOx是造成大气污染的化学物质之一,因此,消除NOx是环境保护的一项重要任务,目前比较成熟的消除NOx工艺是用氨为还原剂和V2O5/TiO2为催化剂的选择催化还原(SCR)法[1],但其成本过高.     

聚丙烯酰胺凝胶法合成TbFeO3 纳米颗粒及其可见光催化活性

采用聚丙烯酰胺凝胶法制备了TbFeO3纳米颗粒, 研究了不同络合剂对样品的纯度、 颗粒尺寸及形貌的影响. XRD分析结果表明, 以酒石酸、 柠檬酸或乙二胺四乙酸(EDTA)为络合剂, 在650 ℃下烧结均可制备出单相TbFeO3纳米颗粒, 但产物的平均粒径不同; 而采用乙酸或草酸为络合剂则难以制得纯相样品. SEM观测结果表明, 以酒石酸为络合剂制备的颗粒细小, 均匀、 形貌规整、 呈球状, 平均粒径约为50 nm; 以柠檬酸为络合剂制备的颗粒主要以近球形为主, 颗粒的尺寸分布相对较宽, 平均粒径约为100 nm; 以EDTA为络合剂制备的颗粒主要呈椭球状, 颗粒尺寸较均匀, 但颗粒间存在不同程度的黏连现象, 平均粒径约为110 nm. 这3种样品的BET比表面积分别为15.4, 8.3和6.8 m2/g. 紫外-可见漫反射吸收光谱研究表明, TbFeO3纳米颗粒的带隙为1.95~1.98 eV. 分别以甲基橙(MO)、 罗丹明B(RhB)、 亚甲基蓝(MB)、 酸性品红(AF)和刚果红(CR)5种有机染料为目标降解物, 考察了TbFeO3颗粒的光催化活性. 结果表明, 在可见光辐照下颗粒表现出良好的光催化活性, 其中, 以酒石酸为络合剂制备的样品光催化效果最好.     

Large-Scale Synthesis of Porous Bi2O3 with Oxygen Vacancies for Efficient Photodegradation of Methylene Blue

Photocatalytic degradation of organic pollutants has become a hot research topic because of its low energy consumption and environmental-friendly characteristics. Bismuth oxide (Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document}) nanocrystals with a bandgap ranging from 2.0 eV to 2.8 eV have attracted increasing attention due to high activity of photodegradation of organic pollutants by utilizing visible light. Though several methods have been developed to prepare Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document}-based semiconductor materials over recent years, it is still difficult to prepare highly active Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} catalysts in large scale with a simple method. Therefore, developing simple and feasible methods for the preparation of Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} nanocrystals in large scale is important for the potential applications in industrial wastewater treatment. In this work, we successfully prepared porous Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} in large scale via etching commercial BiSn powders, followed by thermal treatment with air. The acquired porous Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} exhibited excellent activity and stability in photocatalytic degradation of methylene blue. Further investigation of the mechanism witnessed that the suitable band structure of porous Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} allowed the generation of reactive oxygen species, such as O\begin{document}$ _2 $\end{document}\begin{document}$ ^{-\cdot} $\end{document} and \begin{document}$ \cdot $\end{document}OH, which effectively degraded MB.