金属和非金属共掺杂TiO_2催化剂光催化活性研究

采用溶胶-凝胶法制备了B、N和Ce共掺杂TiO2光催化剂,并用XRD、SEM等表征了其结构特征。以酸性大红染料为模型化合物,探索了其光催化性能,同时考察了制备条件对共掺杂TiO2催化剂活性的影响。结果表明,当B、N和Ce的原子为1∶2∶0.1时,光催化剂活性最大,大红染料的降解率达到98%。     

Visible photocatalytic properties of vanadium doped zinc oxide aerogel nanopowder

Vanadium-doped zinc oxide nanoparticles have been synthesized by sol-gel method. In our approach the water for hydrolysis used in the synthesis of nanopowder was slowly released followed by a thermal drying in ethyl alcohol at 250 °C. The obtained nanopowder was characterized by various techniques such as particle size analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). In the as-prepared state, the powder with an average particle size of 25 nm presents a strong luminescence band in the visible range. From photoluminescence excitation (PLE) the energy position of the obtained PL band depends on the excitation wavelength and this PL band can be also observed under visible excitations. This result is very promising for visible photo catalysis applications, which was confirmed by methylene blue photo-degradation using visible lamp as a light source.     

单体和催化剂浓度对PA有机气凝胶结构的影响

以碳酸钠(C)为催化剂、乙醇为溶剂,间苯三酚(P)-乙醛(A)为反应前躯体,经溶胶-凝胶、交联老化、二氧化碳超临界干燥制备出间苯三酚-乙醛有机气凝胶(PA)。PA有机气凝胶的孔结构和密度可以通过改变反应物浓度和间苯三酚与催化剂的摩尔比(P/C)来进行调解。用P/C摩尔比为100、300、500制备一系列不同理论密度PA有机气凝胶。SEM和氮气吸附测试结果表明,单体和P/C的摩尔比主要影响PA有机气凝胶的比表面积、孔容和平均孔径,而对微孔影响不大。     

Synthesis and photocatalytic activity of titania microspheres with hierarchical structures

A combined sol-gel and solvothermal process was introduced to fabricate the titania microspheres with hierarchical structures by using lauryl alcohol as the structure-directing agent. Scanning electron microscope, high-resolution transmission electron microscope, Fourier transform infrared spectrograph and powder X-ray powder diffraction indicated that the molar ratio of lauryl alcohol, water and tetra-n-butyl titanate was the key factor for the formation of the mono-dispersed titania with anatase phase and the optimal ratio was 1.2:4:1. The diameter of the end-product was 523 ± 74 nm and it was composed of smaller nanoparticles with about 6.8 nm size in diameter. Photocatalytic activity of the end-product was investigated by employing Rhodamine B and Methylene blue as the model compounds. The target microspheres exhibited the higher photocatalytic efficiency compared with commercial Degussa P25 titania and this result might be due to the hierarchical structures of microspheres according to the analysis of Brunauer-Emmett-Teller specific surface areas.     

Controlled release of small molecules from silica xerogel with limited nanoporosity

Conventional sol–gel processing requires several distinct steps involving hydrolysis, condensation and drying to obtain a highly porous, glassy solid material. With the goal of achieving controlled release of small molecules, herein we focus on the acceleration of the condensation and drying steps by casting the hydrolyzed sol on a large open surface to achieve a denser 100 % silica xerogel structure. Thus, cast xerogel with a more limited porosity was prepared. The effect of synthesis parameters during sol–gel synthesis on the release kinetics of bupivacaine, vancomycin and cephalexin was investigated. The release kinetics fitted well with the Higuchi model, suggesting a diffusional release mechanism. Combining the release and nanostructure data, the formation mechanism of cast xerogel is described. Without introducing additional precursors or additives into sol–gel systems, sol–gel casting is an easy technique that further expands the applicability of sol–gel materials as excellent carriers for the controlled release of a variety of drugs.     

Magnetically separable composite photocatalyst with enhanced photocatalytic activity

A novel magnetically separable composite photocatalyst, anatase titania-coated magnetic activated carbon (TMAC), was prepared in this article. In the synthesis, magnetic activated carbon (MAC) was firstly obtained by adsorbing magnetic Fe₃O₄ nanoparticles onto the activated carbon (AC), and then the obtained MAC was directly coated by anatase titania nanoparticles prepared at low temperature (i.e. 75 °C). The prepared samples were characterized by XRD, SEM and vibrating sample magnetometer (VSM). The composite photocatalyst can be easily separated from solution by a magnet, its photocatalytic activity in degradation of phenol in aqueous solution also has dramatic enhancement compared to that of the neat titania.     

Nanostructured porous ZnO film with enhanced photocatalytic activity

Well-defined ZnO nanostructured films have been fabricated directly on Zn foil via hydrothermal synthesis. During the fabrication of the ZnO nanostructured films, the Zn foil serves as the Zn source and also the substrate. Porous nanosheet-based, nanotube-based and nanoflower-based ZnO films can all be easily prepared by adjusting the alkali type, reaction time and reaction temperature. The composition, morphology and structure of ZnO films are characterized by X-ray diffraction, scanning electron microscope and high-resolution transmission electron microscope. The porous ZnO nanosheet-based film exhibits enhanced photocatalytic activity in the degradation of Rhodamine B under UV light irradiation. This can be attributed to the high surface area of the ZnO nanosheet and the large percentage of the exposed [001] facet. Moreover, the self-supporting, recyclable and stable ZnO photocatalytic film can be readily recovered and potentially applied for pollution disposal.     

Phase- and size-controllable synthesis with efficient photocatalytic activity of ZnS nanoparticles

We report a simple solution-based method to synthesize phase- and size-controllable ZnS nanoparticles at low temperature. Cubic ZnS (c-ZnS) and hexagonal ZnS nanoparticles (h-ZnS) were obtained by heating an aqueous solution of Zn(NO₃)₂·6H₂O and Na₂S₂O₃·5H₂O at different temperatures. When the system was heated at 65 °C for 24 h, hexagonal crystal structure of ZnS nanoparticles, with size of 50–350 nm, was obtained, as confirmed by X-ray diffraction and selected-area electron diffraction. When the reaction temperature was 100 °C under hydrothermal condition, c-ZnS nanoparticles were obtained and exhibited monodisperse nanoparticles with average size of 4 nm. Proper rate of S releasing tuned by the variation of pH value is believed to be critical to stabilize the hexagonal ZnS nanoparticles. Compared with large size of h-ZnS nanoparticles, c-ZnS nanoparticles show higher photocatalytic activity in degrading methyl orange (MO). The degradation efficiency of c-ZnS nanoparticles reaches 97% under UV irradiation for 120 min. The good ultraviolet absorbing ability, charge separation property, and large surface area of c-ZnS nanoparticles are believed to have a positive impact on improving the degradation rate and degradation efficiency of MO.     

具有可见光活性的TiO2薄膜的制备及光催化性能

运用磁控溅射技术在浸渍－提拉法制得的TiO2薄膜上溅射三氧化钨层得到光催化薄膜。采用SEM、XRD、AES、UV－vis漫反射光谱等方法表征催化剂薄膜的厚度、晶相结构、化学元素组成及光吸收性能。以甲基橙的光催化降解为反应模型，高压汞灯为光源，溅射有三氧化钨薄膜的光催化活性低于纯TiO2薄膜；滤过紫外光后，溅射有三化钨的薄膜光催化活性明显高于纯TiO2薄膜。本实验提供了一种制备高可见光活性的TiO2薄膜的方法。     

钛酸盐纳米棒的制备及其光催化活性研究

采用水热法制备了钛酸盐纳米棒,样品再分别经400、500、600和800℃热处理2h.利用XRD、SEM、TEM、BET、UV-vis等手段对样品的物化性能进行了表征.以4-氯硝基苯为目标反应物考察了样品的光催化活性.结果表明,钛酸盐纳米棒具有较高的热稳定性,直径分布在50～150nm,长度可达几微米.光催化结果显示,4-氯硝基苯的光催化降解反应为动力学拟一级反应,并且经500℃热处理后的钛酸盐纳米棒具有最高的催化活性,其表观速率常数为0.04215min-1,是普通商用TiO2粉末的两倍.     

Synthesis and photocatalytic activity of anatase-based aerogels

V_xTi_1–xO₂ (x = 5 and 10 mol %) solid solutions have been synthesized through supercritical drying in isopropanol at t = 250°C and p = 10 MPa. Their physicochemical properties and photocatalytic performance have been compared to those of an earlier synthesized Zn_xTi_1–xO₂ aerogel containing 10 mol % Zn [1]. It has been shown that increasing the vanadium content of V_xTi_1–xO₂ from 5 to 10 mol % leads to a decrease in hydrogen evolution rate in methanol/water splitting reaction under UV irradiation from 190 to 32 µL/(min g_catal), whereas in the case of the anatase-based aerogel solid solution containing 10 mol % Zn an opposite picture is observed: the hydrogen evolution rate in methanol/water splitting reaction under UV irradiation increases sharply to 700 µL/(min g_catal).     

Synthesis of mesoporous carbon nitride by molten salt-assisted silica aerogel for Rhodamine B adsorption and photocatalytic degradation

Journal of Materials Science - As a new nonmetallic photocatalysis material, it is of great attention to develop the carbon nitride (g-C3N4) with good structure and optical properties. Herein, a...     

Correlation of lattice distortion with photocatalytic activity of titanium dioxide

The photocatalytic activity of titanium dioxide dispersions on X-3B pigment degradation has been investigated. A variety of factors that would influence the photocatalytic activity such as crystallite size, lattice distortion, and anatase content are discussed in detail. It is found that lattice distortion is the most important one among these factors and is expected to inhibit the hole and electron pair recombination. It determines, to some extent, the photocatalytic efficiency of titanium dioxide dispersions.     

Co-electrospinning fabrication and photocatalytic performance of TiO2/SiO2 core/sheath nanofibers with tunable sheath thickness

In this paper, core/sheath TiO₂/SiO₂ nanofibers with tunable sheath thickness were directly fabricated via a facile co-electrospinning technique with subsequent calcination at 500 °C. The morphologies and structures of core/sheath TiO₂/SiO₂ nanofibers were characterized by TGA, FESEM, TEM, FTIR, XPS and BET. It was found that the 1D core/sheath nanofibers are made up of anatase–rutile TiO₂ core and amorphous SiO₂ sheath. The influences of SiO₂ sheath and its thickness on the photoreactivity were evaluated by observing photo-degradation of methylene blue aqueous solution under the irradiation of UV light. Compared with pure TiO₂ nanofibers, the core/sheath TiO₂/SiO₂ nanofibers performed a better catalytic performance. That was attributed to not only efficient separation of hole–electron pairs resulting from the formation of heterojunction but also larger surface area and surface silanol group which will be useful to provide higher capacity for oxygen adsorption to generate more hydroxyl radicals. And the optimized core/sheath TiO₂/SiO₂ nanofibers with a sheath thickness of 37 nm exhibited the best photocatalytic performance.     

Enhanced photocatalytic activity of bismuth molybdate via hybridization with carbon

The bismuth molybdate Bi_3.64Mo_0.36O_6.55 (BMO) was successfully synthesized by a rapid and convenient microwave-assisted method. Carbon was introduced to hybridize with BMO material (BMO/C) through the simple combination of hydrothermal process in the presence of glucose and subsequent calcination treatment in N₂ gas at 280 °C. The products were characterized by the study of X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that carbon did not affect the final crystalline structure of BMO, but it had great influences on the photocatalytic activity of BMO towards rhodamine-B (RhB) degradation. The improved photocatalytic performance could be ascribed to the enhanced photogenerated electron-hole separation and more RhB adsorption associated with carbon.     

银掺杂TiO2光催化剂的制备及光催化性能研究

采用溶胶-凝胶法,以钛酸四丁酯、硝酸银为原料制备了不同银含量掺杂TiO2光催化剂,并以TG-DTA、XRD、TEM对样品进行了表征,XRD结果显示,掺杂银TiO2光催化剂为锐钛矿型,银掺杂量较低时,银均匀分布在TiO2的表面,在掺杂量为4%时,出现银的团聚。光催化亚甲基蓝结果表明,银掺杂TiO2光催化剂比未掺杂TiO2降解率明显提高,在2%银掺杂TiO2光催化剂用量为25mg,pH值为6～8,降解时间为120min,降解率可达93%。