金红石相TiO2-石墨烯复合材料的制备及其光催化性能

以鳞片石墨为原料, 用改进的Hummers法制备氧化石墨烯(GO), 以异丙醇钛为钛源经一步水热法制备得到金红石相TiO₂-石墨烯复合材料(rGO-TiO₂), 考察了氧化石墨烯用量对复合材料光催化性能的影响. 采用X射线衍射(XRD), 比表面积(BET), 透射电镜(TEM), 扫描电镜(SEM), 拉曼光谱, 紫外-可见(UV-Vis)吸收光谱和荧光光谱(PL)等测试手段对复合材料进行表征. 结果表明: 复合材料中TiO₂为针簇状结构的金红石相, 与石墨烯能够均匀复合; 与纯金红石相TiO₂相比, 复合材料具有较大的比表面积. 研究了该复合材料在紫外光下对罗丹明B 以及可见光下对甲基橙光降解效果. 当氧化石墨烯浓度为0.5 mg·mL^-1时, 制备得到的复合材料rGO-TiO₂具有较好的光催化效果.     

GO/TiO2-g-C3N4纳米复合材料的制备及可见光催化性能

以水热法制备的20% g-C₃N₄/TiO₂（20%为质量分数）为基,将其与不同质量分数的氧化石墨烯（GO）复合制备出可见光催化性能优良的GO/TiO₂-g-C₃N₄三元复合材料。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-Vis DRS）、光致荧光光谱（PL）、瞬态光电流响应等分析测试手段对样品的结构、形貌和光电性能进行表征。研究了不同质量分数GO的加入对GO/TiO₂-g-C₃N₄在可见光下降解亚甲基蓝（MB）溶液的影响。结果表明： g-C₃N₄/TiO₂与GO复合后,锐钛矿相TiO₂颗粒形成小团簇附着在g-C₃N₄和GO片层表面,且当GO含量为15%时,TiO₂形成的团簇最小,对可见光的吸收最多且光生电子-空穴对的复合率最低。可见光照射下,15% GO/TiO₂-g-C₃N₄复合材料对MB的降解率在3 h内可达98.4%,且其降解速率常数（0.022 4 min^-1）分别是纯TiO₂（0.001 5 min^-1）和g-C₃N₄/TiO₂（0.002 5 min^-1）的15倍和9倍。     

部分还原氧化石墨烯/二氧化钛复合材料的水热合成及其光催化活性

采用水热法以Hummers氧化法制备的氧化石墨和钛酸四丁酯为原料制备了部分还原的氧化石墨烯/二氧化钛(RGO/TiO₂)复合光催化剂, 并研究了该复合材料在可见光以及紫外光下对亚甲基蓝的光催化降解活性.结果表明, 通过改变反应温度和氧化石墨加入量可以调控TiO₂的晶相组成及其在复合材料中的分散性; 在水热反应过程中氧化石墨烯发生了部分还原; 所制备的RGO/TiO₂复合材料的可见光和紫外光催化活性均高于纯TiO₂; 部分还原的氧化石墨烯在复合材料中担当载体和电子受体, 同时可以使TiO₂的初始吸收边向可见光区域红移, 增强了TiO₂在可见光区域的吸收, 能有效提高对目标污染物的吸附性和光催化降解活性.     

TiO2-双亲共聚物复合纳米粒子的合成与紫外光敏特性

用偶联剂乙烯基三乙氧基硅烷改性纳米粒子TiO₂, 应用超声技术将TiO₂ 纳米粒子分散在甲醇介质中, 然后用苯乙烯(ST)原位聚合包封, 再用丙烯酰胺或乙烯基吡咯烷酮(VP)共聚, 两步原位分散聚合得到了有机聚合物为壳、TiO₂为核的有机/无机复合粒子. 用红外光谱、紫外-可见光谱、透射电子显微镜等检测手段进行表征. 结果显示: 由于双亲共聚物对TiO₂纳米粒子的敏化作用, 紫外-可见光谱图上两种纳米复合粒子的最大吸收峰均有明显红移, 并且吸收光谱的范围扩大了, 其中尤以TiO₂/(PST-co-PVP)为甚. 意味着光敏化活性的提高, 特别是在可见光谱的范围内. 这种情形对宽带隙半导体材料如TiO₂纳米粒子的光催化特性是有利的, 表明这类材料的应用空间得到了拓展.     

TiO2-双亲共聚物复合纳米粒子的合成与紫外光敏特性

用偶联剂乙烯基三乙氧基硅烷改性纳米粒子TiO₂, 应用超声技术将TiO₂ 纳米粒子分散在甲醇介质中, 然后用苯乙烯(ST)原位聚合包封, 再用丙烯酰胺或乙烯基吡咯烷酮(VP)共聚, 两步原位分散聚合得到了有机聚合物为壳、TiO₂为核的有机/无机复合粒子. 用红外光谱、紫外-可见光谱、透射电子显微镜等检测手段进行表征. 结果显示: 由于双亲共聚物对TiO₂纳米粒子的敏化作用, 紫外-可见光谱图上两种纳米复合粒子的最大吸收峰均有明显红移, 并且吸收光谱的范围扩大了, 其中尤以TiO₂/(PST-co-PVP)为甚. 意味着光敏化活性的提高, 特别是在可见光谱的范围内. 这种情形对宽带隙半导体材料如TiO₂纳米粒子的光催化特性是有利的, 表明这类材料的应用空间得到了拓展.     

TiO2/石墨烯复合材料的合成及光催化分解水产氢活性

利用石墨粉根据Hummers氧化法制得氧化石墨,并进一步还原得到石墨烯。采用溶胶-凝胶法以钛酸四丁酯和石墨烯为起始材料制备了二氧化钛(TiO₂)和石墨烯的复合光催化材料。研究了该复合材料在紫外-可见光以及可见光条件下的光催化分解水制氢活性。结果表明,紫外-可见光照射下,TiO₂/石墨烯复合光催化材料的光催化分解水产氢速率为8.6 μmol·h^-1,远大于同条件下商业P25的产氢速率 (4.5 μmol·h^-1),光解水产氢活性提高了近2倍;可见光下光照3 h,TiO₂/石墨烯复合材料的光催化分解水产氢量约为0.2 μmol。     

水热合成部分还原氧化石墨烯-K2Mn4O8超级电容器纳米复合材料

通过控制水热反应温度以及氧化石墨烯(GO)与高锰酸钾的填料比, 合成了两组部分还原的GO-K₂Mn₄O₈纳米复合材料. X射线衍射(XRD)分析说明水热过程中合成了α-MnO₂和一种新的晶相K₂Mn₄O₈.通过X射线光电子能谱(XPS)分析了水热反应前后氧化石墨的含氧官能团的变化. 扫描电子显微镜(SEM)显示样品由片状还原的氧化石墨烯构成, 其表面附有许多小的纳米颗粒, 这种结构有利于储能时电子的传递. 通过这两组复合材料的结构分析, 更好地理解了材料的电化学性能的变化. 利用循环伏安法和恒流充放电测试比较了材料的电容性能. 用1 mol·L^-1的硫酸钠做电解液, 电位范围是0-1 V, 在1 A·g^-1的电流密度下, 测得的样品最佳比电容达到251 F·g^-1, 能量密度为32 Wh·kg^-1, 功率密度为18.2 kW·kg^-1. 并且在5 A·g^-1的电流密度下循环1000次后样品的比电容仍维持在初始比电容的88%.     

双介孔结构的纳米TiO2/I2复合材料的制备及其可见光催化性能

以钛酸丁酯为前驱体, 碘溶胶为碘源, 在室温下采用水解沉淀法制备了单质碘和纳米TiO₂复合的双介孔结构光催化剂(M-I₂-TiO₂). 采用X射线衍射(XRD)、透射电子显微镜(TEM)、比表面分析(BET)、紫外-可见(UV-Vis)漫反射光谱和傅里叶变换-红外光谱(FT-IR)对M-I₂-TiO₂进行了表征. 以次甲基蓝(MB)溶液为模拟废水, 对M-I₂-TiO₂的光催化性能进行了评价, 研究了不同热处理温度对光催化活性的影响. 结果表明, M-I₂-TiO₂在可见光区有显著的吸收, 300 ℃热处理得到的样品比表面积高达227.6 m²/g, 600 ℃热处理所得样品的比表面积仍高达111.8 m²/g, 而400 ℃热处理所得样品具有最好的光催化降解性能. 双介孔结构纳米TiO₂/I₂复合材料的光催化降解性能显著高于相同方法制备的纯TiO₂和Degussa P-25商业产品. 催化剂经6次重复使用其光催化活性基本保持不变.     

氧化环境和比例对改性Hummers法制备GO的影响

以鳞片石墨(GR)为原料,采用改性Hummers法液相氧化方法制备氧化石墨,通过超声剥离的方法剥离出片状的氧化石墨烯(GO),探讨了H₂SO₄环境与H₂SO₄+H₃PO₄混酸环境和KMnO₄与GR的比例对GO制备的影响。采用FTIR、UV、TG、XRD、SEM和XPS等分析手段对制备的GO进行分析。结果表明：GO外貌是呈褶皱片状,在片层上主要有C=O、C-OH、-COOH和C-O-C等官能团,以共价键形式存在石墨层间;通过TG与XPS数据分析表明在H₂SO₄ H₃PO₄混酸环境下制备的GO含氧官能团较多,并且(KMnO₄)与鳞片石墨的最佳比例是1:4。     

溶胶-凝胶-水热晶化法制备锐钛矿TiO2纳米膜的耐蚀性能

以钛酸正丁酯为前驱体, 采用溶胶-凝胶-水热晶化法在不锈钢(SS)表面制备TiO₂纳米膜. 利用X射线衍射(XRD)、Raman光谱、场发射扫描电子显微镜(SEM)、原子力显微镜(AFM)和俄歇电子能谱(AES)表征了TiO₂纳米膜的晶型、表面形貌和表面化学组成. 通过极化曲线和电化学阻抗谱(EIS)研究了TiO₂纳米膜的耐蚀性能. 170 °C下水热晶化制备的锐钛矿TiO₂与450 °C焙烧制备的锐钛矿TiO₂的结晶度类似, 但两种TiO₂薄膜的表面结构存在明显差异, 水热晶化法制备的TiO₂纳米膜在3.5% (w) NaCl溶液中的耐蚀性能优于焙烧法制备的.     

Doping of TiO2–GO and TiO2–rGO with Noble Metals: Synthesis,Characterization and Photocatalytic Performance for Azo Dye Discoloration

The nanocomposites of titania coupled with graphene oxide (GO) and reduced graphene oxide (rGO), respectively, were prepared by homogeneous hydrolysis with urea. Graphene was obtained by effect of high‐intensity cavitation field on natural graphite in the presence of strong aprotic solvents in pressurized ultrasonic reactor. The morphology of TiO₂–GO and TiO₂–rGO composites was assessed by scanning electron microscopy and atomic force microscopy. The nitrogen adsorption–desorption was used for determination of surface area (BET) and porosity. Raman and IR spectroscopy were used for qualitative analysis and diffuse reflectance spectroscopy was employed to estimate band‐gap energies. Further enhancement of the photocatalytic activity was attained by codoping of composites with noble metals—Au, Pd and Pt. The photocatalytic activity of TiO₂–GO and TiO₂–rGO were assessed by photocatalytic decomposition of Orange II dye in an aqueous slurry under UV and visible light irradiation. The photocatalytic activity of noble metals codoped samples was determined with decomposition of Reactive Black 5 azo dye.     

Preparation of mesoporous TiO2/CNT nanocomposites by synthesis of mesoporous titania via EISA and their photocatalytic degradation under visible light irradiation

Stabilized mesoporous TiO₂ was synthesized by evaporation induced self assembly (EISA) method and mechanically incorporated into single-walled carbon nanotubes (SWCNT) with different ratios. The physicochemical properties of the nanocomposites (mesoporous TiO₂/SWCNT) materials were investigated by Brunauer–Emmett–Teller (BET) measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), photoluminescence (PL) and ultraviolet–visible (UV–Vis) spectroscopy measurements. The catalytic activity of mesoporous TiO₂ and nanocomposites were assessed by examining the degradation of rhodamine B as model aqueous solution under visible light. CNTs are facilitating the photocatalytic activity of mesoporous TiO₂ in the degradation of rhodamine B efficiently.     

Template‐free Fabrication of Hierarchical Macro‐/mesoporous N‐doped TiO2/graphene Oxide Composites with Enhanced Visible‐light Photocatalytic Activity

Hierarchical macro‐/mesoporous N‐doped TiO₂/graphene oxide (N‐TiO₂/GO) composites were prepared without using templates by the simple dropwise addition mixed solution of tetrabutyl titanate and ethanol containg graphene oxide (GO) to the ammonia solution, and then calcined at 350 °C. The as‐prepared samples were characterized by scanning electron microscopy (SEM), Brunauer‐Emmett‐Teller (BET) surface area, X‐ray diffraction (XRD), Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and UV‐Vis absorption spectroscopy. The photocatalytic activity was evaluated by the photocatalytic degradation of methyl orange in an aqueous solution under visible‐light irradiation. The results show that N‐TiO₂/GO composites exhibited enhanced photocatalytic activity. GO content exhibited an obvious influence on photocatalytic performance, and the optimal GO addition content was 1 wt%. The enhanced photocatalytic activity could be attributed to the synergetic effects of three factors including the improved visible light absorption, the hierarchical macro‐mesoporous structure, and the efficient charge separation by GO.     

Synthesis of 3D hierarchical porous TiO2/InVO4 nanocomposites with enhanced visible-light photocatalytic properties

Three-dimensional (3D) hierarchical porous TiO₂/InVO₄ nanocomposites were fabricated by loading TiO₂ nanoparticles on the surface of porous InVO₄ microspheres. X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectroscopy and photoluminescence spectroscopy (PL) were adopted to analyze the structure–property relationship of samples. The results show that the surface of as-prepared TiO₂/InVO₄ nanocomposites are composed of uniformly interconnected bi-phase nanocrystals, forming a close interface between these two components, which is favorable for the highly efficient interparticle electron transfer to achieve enhanced photocatalytic properties. However, the adsorption ability is decreased due to the loading of TiO₂ nanoparticles on the surface of InVO₄. Therefore, under the joint action of these factors, the TiO₂/InVO₄ nanocomposites achieve the best photocatalytic activity when the mole ratio of In:Ti reaches 4:1, and the visible-light photocatalytic activity is about as 3.3 times high as that of pure InVO₄ without modification.     

Liquid crystalline polymers XVI*. Thermotropic liquid crystalline copoly(arylidene-ether)/TiO2 Nanocomposites: synthesis,characterisation and applications

ABSTRACT

Polymer nanocomposites are already a part of many important worldwide businesses. Among many nanocomposite precursors, titanium dioxide (TiO₂) nanopowder is increasingly being investigated due to its special properties. In this work, the feasibility of synthesising a new series of materials, copoly(arylidene-ether)/titanium dioxide nanocomposites, using in-situ copolymerisation technique has been investigated. This can be performed by the interaction of both cyclohexanone and 4-tert-butylcyclohexanone monomers with 4,4′-diformyl-2,2′-dimethoxy-α,ω-diphenoxyalkanes Ia–e, respectively, using different additions of titanium dioxide-P25. The structure of the prepared nanocomposites IIa–e/TiO₂ (0.2–3.0%) was confirmed by elemental analysis (energy dispersive X-ray spectroscopy) and spectral data (Fourier transform-infrared [FT-IR]). FT-IR verified the dispersion of nanofillers in the copolymer. Then, the characterisation and applications of these nanocomposites are extensively discussed depending on the investigation of how the addition of titanium dioxide nanoparticles affected on their properties using various techniques, such as X-ray diffraction, SEM, transmission electron microscopy, Water Contact Angle (WCA), thermogravimetric analysis, differential thermogravimetric, differential thermal analysis (DTA), polarising optical microscope and UV–vis absorption spectroscopy. The nanoparticles affected on the copolymer thermal behaviour in different ways (discrepancy results) depending on how these nanoparticles are dispersed in the copolymer matrix. UV–vis absorption spectra displayed a decrease in the optical band gap of some nanocomposites, which resulted from the addition of titanium dioxide to these copolymers, and this can improve the efficiency of them as organic emitting materials.     

Cooperation among N,F and Fe in tri-doped TiO<Subscript>2</Subscript> photocatalyst

TiO₂ photocatalysts tri-doped with N, F and Fe were synthesized by a sol–gel method. The cooperation of N, F and Fe in tri-doped TiO₂ was verified by monitoring NH₃ decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption spectroscopy, and by the simulation based on the density functional theory (DFT). The results from NH₃ decomposition revealed that the cooperation of N, F and Fe broadened the optical response of TiO₂ to the visible light range and also enhanced the photocatalytic activity of TiO₂ under UV light. The reusability of the tri-doped TiO₂ sample after three cycles under UV and visible light irradiation was very good. XRD patterns and SEM and HRTEM images indicated that the tri-doped sample was nanometric anatase with a small amount of rutile with an average particle size of 18 nm. Tri-doping with N, F and Fe suppressed the phase transition from anatase to rutile and also resulted in some more lattice defects. XPS analysis showed that the N, F and Fe atoms were doped into the TiO₂ lattice. UV–Vis absorption spectra of the tri-doped TiO₂ showed that its optical absorption edge was moved up to 640 nm and its UV absorption was also enhanced. The DFT results confirmed that the cooperation of Fe 3d and N 2p orbits narrowed the band gap of TiO₂ and the F 2p orbit broadened the upper valence bands. The synergistic electron density around N, F and Fe in tri-doped TiO₂ was capable of enhancing the photochemical stability and reusability of TiO₂.     

Microwave-hydrothermal synthesis and photocatalytic properties of biomass charcoal/TiO2 nanocomposites

Biomass charcoal-doped titanium dioxide (C/TiO₂) composites were proposed by microwave-hydrothermal and calcination method using tetrabutyl titanate as the titanium source and lignin as the carbon source. TiO₂ crystals with different morphologies could be successfully adsorbed onto the surface of biomass charcoal. These products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), derivative thermogravimetric (DTG), UV–vis diffuser flection spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET). The photocatalytic activities of the as-obtained composites were checked under visible light irradiation. The results showed that both the microwave-hydrothermal temperature and time played an important role in the microstructure and photocatalytic activity of the samples. The rapid microwave-hydrothermal with the thermal post-treatment provides a promising route for the fabrication of biomass charcoal-doped nanocomposites materials.     

光驱动多孔无定形TiO2的形成机制与光催化性能的研究

以钛酸正丁醇和乙二醇为原料,采用溶剂热法合成了钛乙二醇盐(TG)前躯体,在高压汞灯照射下制备出无定形TiO2。利用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)、紫外-可见吸收光谱(UV-Vis)、表面光电压谱(SPS)、N2吸附-脱附对所得材料进行了结构和性能的表征。借助X射线吸收精细结构(XAFS)对无定形TiO2的形成机制进行了分析,并通过硝基苯的还原反应考察了材料的光催化性能。结果表明:在紫外光驱动无定形TiO2的形成过程中,中心元素Ti4+的配位环境发生变化,由八面体结构转变为四面体结构;由于特殊的孔道结构使得多孔无定形TiO2显示出较好的光催化活性。     

Single-step solvothermal synthesis of mesoporous anatase TiO<Subscript>2</Subscript>-reduced graphene oxide nanocomposites for the abatement of organic pollutants

In the present work, we have fabricated a novel mesoporous TiO₂–rGO nanocomposite by a facile one-step solvothermal method using titanic sulfate as the TiO₂ source. The as-prepared composites were characterized by transmission electron microscopy, X-ray diffraction; UV–Vis diffuse reflectance spectra, X-ray photoelectron spectroscopy and photoluminence spectra. In situ nucleation and anchoring of TiO₂ nanoparticles onto a graphene sheet is favorable fpr forming an intimate interfacial contact, and the chemically bonded TiO₂–rGO nanocomposites commendably enhanced their photocatalytic activity in the photodegradation of rhodamine B and phenol. The high photocatalytic activity of the as-synthesized nanocomposites are primarily ascribed to the mesoporous structure, efficient charge transportation and separation with enhanced visible light absorption, which come from the appealing nanoarchitecture, for instance, ultra-dispersed and ultra-small TiO₂ nanocrystals along with intimate and absolute interfacial contact between the TiO₂ nanocrystals and the graphene sheet.     

Self-assembled fabrication and flame-retardant properties of reduced graphene oxide/waterborne polyurethane nanocomposites

The graphite oxide (GO) was prepared from expandable graphite by the pressurized oxidation method, and samples were characterized using XRD, UV–Vis, and TEM. GO is reduced in situ emulsion using hydrazine to achieve reduced graphene oxide/waterborne polyurethane (rGO/WPU) nanocomposites. The effect of rGO content on the stability, fracture morphologies, mechanical performance, thermal degradation, and flame-retardant properties of rGO/WPU composites was investigated by zeta potential analyzer, TEM, SEM, universal testing machine, TG, and Cone Calorimeter. The results of zeta potential, TEM, and SEM analysis indicate that rGO has a good stability and dispersibility in rGO/WPU nanocomposites. The results of mechanical tests showed that the mechanical properties of rGO/WPU nanocomposites increased consistently with increasing rGO content up to 2 mass%, and TG showed that the thermostability of rGO/WPU nanocomposites decreased slightly compared to pure WPU, but carbon residue increased from 0.99 to 1.99 % when the mass fraction of rGO in WPU is 2 %. Cone Calorimeter test indicated that the flame-retardant and smoke suppression properties of rGO/WPU composites showed significant improvement compared to the WPU alone. When the mass fraction of rGO is 1 %, the total smoke release and smoke factor decreased by 25 and 38 %, respectively, compared to those of pure WPU.