Amorphous SiCNO hollow nanofibers with mesoporous walls

In this work, for the first time, we reported the fabrication of polymer-derived amorphous SiCNO ceramics via electrospinning of tetraethoxysilane (TBOS), polyvinylpyrrolidone (PVP), cetrimonium bromide (CTAB), and urea combined with subsequent air calcination. The resultant products exhibited a well-defined one-dimensional (1D) hollow fiber nanostructure with mesoporous walls. The BET surface area of SiCNO hollow nanofibers is ~95.6 m²/g, and the average pore diameter is sized in ~9 nm. The movement of urea within the core of the as-spun polymeric fibers accounted for the formation of hollow nanofibers, and the thermal decomposition of polymers such as PVP, TEOS, and urea responded for the formation of mesopores within the walls. In addition, it was found that the contents of urea within the raw materials played a critically important role in the formation of SiCNO mesoporous hollow nanofibers, making their growth in a controlled manner.     

二氧化钛介孔材料的制备

基于溶胶-凝胶过程,以十六烷基溴化铵为模板剂,合成了TiO2以及V/Ce/F-TiO2 介孔材料。利用XRD、Ｎ２吸附、TEM、TG-DTA和UV-Vis DRS等手段表征了材料的晶相组成、晶粒尺寸、介孔结构、热稳定性及吸光性能。通过系统研究表明,延长凝胶时间和优化陈化工艺可以得到TiO2介孔材料。TiO2和V/Ce/F/TiO2的平均孔径为3.1～5.1 nm,最大比表面积可达189 m2/g。焙烧温度大于450 ℃脱除模板剂时可引起孔道的塌陷,而掺杂V/Ce/F后可稳定材料的介孔结构。相对于纯TiO2光催化剂,掺杂V/F的TiO2吸光带边红移至可见光区。     

TiO2中空纤维的制备及光催化性能

采用模板法制备了不同温度的TiO2中空纤维光催化材料,并利用X射线衍射、扫描电镜对其晶型及表面形貌进行了表征.以亚甲基蓝(MB)的脱色降解为模式反应,考察了温度对TiO2中空纤维光催化性能的影响.     

有序介孔TiO2材料的合成、表征与应用

有序介孔材料是近年来新兴起的一个研究热点,非硅基有序介孔材料在光催化、磁、电等诸多领域存在巨大的潜在应用价值.而TiO2以其特有的光催化活性、紫外光屏蔽效应等功能,以及化学性质稳定、毒性低、价格便宜和易于回收等特点,尤其值得关注.笔者综合阐述了有序介孔TiO2材料的合成过程、合成机理以及材料的表征和应用前景等情况.     

TiO2 and TiO2/Ag nanofibers: template synthesis,structure, and photocatalytic properties

Journal of Porous Materials - A fairly simple method for the synthesis of TiO2 and TiO2/Ag fibers containing the anatase–rutile-silver heterojunction with a combination of features attractive...     

TiO2 nanofibers doped with rare earth elements and their photocatalytic activity

In the present study rare earth doped (Ln³⁺–TiO₂, Ln = La, Ce and Nd) TiO₂ nanofibers were prepared by the sol–gel electrospinning method and characterized by XRD, SEM, EDX, TEM, and UV-DRS. The photocatalytic activity of the samples was evaluated by Rhodamine 6G (R6G) dye degradation under UV light irradiation. XRD analysis showed that all the synthesized pure and doped titania nanofibers contain pure anatase phase at 500 °C but at 700 °C it shows both anatase and rutile phase. XRD result also shows that Ln³⁺-doped titania probably inhibits the phase transformation. The diameter of nanofibers for all samples ranges from 200 to 700 nm. It was also observed that the presence of rare-earth oxides in the host TiO₂ could decrease the band gap and accelerate the separation of photogenerated electron–hole pairs, which eventually led to higher photocatalytic activity. To sum up, our study demonstrates that Ln³⁺-doped TiO₂ samples exhibit higher photocatalytic activity than pure TiO₂ whereas Nd³⁺-doped TiO₂ catalyst showed the highest photocatalytic activity among the rare earth doped samples.     

Template-assisted hydrothermal synthesis and photocatalytic activity of novel TiO2 hollow nanostructures

TiO₂ hollow nanostructures were successfully synthesized by a controlled hydrothermal precipitation reaction using Resorcinol–Formaldehyde resin spheres as templates in aqueous solution, and then removal of the RF resins spheres by calcination in air at 450 °C for 4 h. The obtained TiO₂ hollow spheres were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N₂ adsorption–desorption analysis, and UV–visible diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of rhodamine B aqueous solution at ambient temperature under UV illumination. The results indicated TiO₂ hollow nanostructures exhibit the excellent photocatalytic activity probably due to the unique hollow micro-architectures.     

Synthesis and enhanced photocatalytic activity of Mn/TiO2 mesoporous materials using the impregnation method through CVC process

TiO₂ particles were prepared by chemical vapor condensation and used to synthesize MnO_x/TiO₂ mesoporous materials by impregnation. The Mn-doped TiO₂ particles were smaller (8.5?nm vs. 10.5?nm) and had greater surface areas (203.7?m²?g^?1 vs. 134.4?m²?g^?1) than undoped particles. They were also smaller and had a greater surface area than similarly doped commercial P25, indicating highly dispersed Mn species on the surfaces of the crystalline TiO₂. The resulting materials?? photocatalytic activities towards methylene blue decomposition were compared: the synthesized TiO₂ particles with MnO₂ showed higher photocatalytic activity than the similarly doped commercial P25.     

Fabrication of chain-like TiO2 hollow microspheres with enhanced photocatalytic activity

TiO₂ hollow microspheres (TiO₂-HMSs) have attracted much attention due to their low density, high photoreactivity and easy recovery. However, fabrication of TiO₂-HMSs is time-consuming and costly. In this paper, effect of H₂O₂ on the formation of chain-like TiO₂-HMSs was studied using (NH₄)₂TiF₆ as titanium source and urea as neutralizer through a one-pot hydrothermal reaction strategy. The prepared TiO₂-HMSs were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscopy (SEM). The photocatalytic activity of TiO₂-HMSs was evaluated by photocatalytic degradation of an anionic dye X3B under UV irradiation. It was found that the presence of H₂O₂ not only influences the nucleation, but also enhances the hollowing process of TiO₂-HMSs by accelerating the “inside-outside” mass transfer. TiO₂-HMSs prepared in the presence of H₂O₂ showed enhanced photocatalytic activity due to the synergistic effects of well crystallization and hollow structures.     

光催化介孔玻璃微珠载体材料的研究

利用分相法酸浸制备了Na2O-B2O3-SiO2-Al2O3-TiO2系统的多孔玻璃微珠.当玻璃的成分(质量分数)为Na2O7.50%,B2O3 29.20%,SiO2 61.80%,A12O3 1 5%和TiO2 0.5%时,分相温度590℃和时间为24h,酸浓度和处理时间为0.1 mol/LHCl和48 h时,可制备出孔径分布小于50 nm的光催化载体材料.     

Rational design of mesoporous LiFePO4@C nanofibers as cathode materials for energy storage

In this work, the mesoporous LiFePO₄@C nanofibers have been successfully fabricated through a facile electrospinning method. The structure, morphology, chemical composition and lithium storage performance have been systematically investigated. The results reveal that the LiFePO₄ grains with particle size of ～15 nm are uniformly dispersed in the mesoporous carbon nanofibers. The LiFePO₄@C electrode presents a high reversible capacity and excellent rate performance. It delivers a discharge capacity of 107 mAh g⁻¹ and retains 105 mAh g⁻¹ over 200 cycles at 10C. The excellent electrochemical performances are attributed to the novel nanostructure where LiFePO₄ nanoparticles are embedded in the carbon fibers. This designed structure can significantly enhance the conductivity of LiFePO₄@C, accelerate the diffusion of electrolyte, and thus facilitate the transport of electrons and Li-ions.     

Nb,F-codoped TiO2 hollow spheres with high visible light photocatalytic activity

Nb, F-codoped TiO₂ hollow spheres (NFTSs) were successfully synthesized via a hydrothermal method with niobium oxide, hydrofluoric acid, and tetrabutyl titanate. The obtained spheres were hollow, with a diameter of about 2 μm, and the sphere wall was made up of nanorods arranged close together. The NFTSs presented anatase phase with more {001} facets exposed, which could be mainly attributed to F ions which were preferentially adsorbed on the {001} facets during the crystal growth process. Ti³⁺ states in NFTSs were increased due to Nb, F-codoping, resulting in the decrease of the band gap and the red shift of the absorption edge of the NFTSs. The NFTSs exhibited 20.1% higher photocatalytic speed compared to P25 on the degradation of methylene orange.     

Novel CdIn2S4 nano-octahedra/TiO2 hollow hybrid heterostructure: In-situ synthesis,synergistic effect and enhanced dual-functional photocatalytic activities

The development of highly efficient and multifunctional composite photocatalysts for both energy conversion and environmental governance has obtained great concerns. Here, a novel CdIn₂S₄/TiO₂ (CIS/THS) hollow composite photocatalyst was firstly designed and synthesized via a facile in-situ growth process, where the CdIn₂S₄ nano-octahedra densely attached on the surface of TiO₂ hollow spheres to form the unique hybrid heterostructure. The as-synthesized CIS/THS heterojunctions exhibit much superior photocatalytic activities for hydrogen evolution and Methyl Orange (MO) decomposition in comparison to pure CdIn₂S₄ and TiO₂ hollow spheres. The experimental results display that the CIS/THS-3 sample with the 30 wt% of TiO₂ presents the optimal photocatalytic H₂ production efficiency and its generation rate is 3.38 and 2.56 times as high as those of pure TiO₂ and CdIn₂S₄. Besides, the as-synthesized CIS/THS-3 hybrid also possesses the best MO photodegradation performance and its rate constant is 11.43 and 8.34 times higher than those of pure TiO₂ and CdIn₂S₄. The enhanced photocatalytic activities can be assigned to the synergistic effect, optimized light-harvesting capacity and the formation of hybrid heterostructure for boosting interfacial charge transfer and separation. Furthermore, based on the trapping experiments and ESR analysis, the possible type-Ⅱ interface charge transport mechanism was also proposed. Our study may provide the direct guidance for constructing other hollow TiO₂-based composite photocatalysts with superior photocatalytic water splitting and degradation performances.     

SnO2/ZnO复合中空纤维材料的制备及其光催化性能

采用天然棉花为模板制备了具有高光催化活性的SnO2/ZnO复合中空纤维光催化材料;利用X-射线衍射(XRD)、扫描电子显微镜(SEM)技术对其相结构和形貌进行了表征;以亚甲基蓝(MB)的脱色降解为模型反应,考察了Sn4+和Zn2+物质的量比为0.1∶1时煅烧温度对其催化性能的影响。实验结果表明:制备的样品为复制了棉花纤维模板形貌、具有中空结构的SnO2和ZnO半导体复合材料(SnO2/ZnO);煅烧温度对材料SnO2/ZnO的结晶度、晶粒大小﹑表面微结构和催化性能等有显著影响;650℃左右所得样品在太阳光下的催化活性最好,1 h可使MB溶液的脱色降解率达100%;该材料易于离心分离,具有良好的催化活性和重复使用性能。     

Tb掺杂介孔TiO_2/聚噻吩复合材料的制备及其可见光光催化性能研究

采用原位聚合法制备了一系列不同质量比m(Th)/m(Tb掺杂介孔TiO2)的复合光催化剂(其中Th为噻吩),采用XRD、FTIR、荧光光谱(PL)、场发射透射电镜(FETEM)和X射线光电子能谱(XPS)对复合光催化剂进行了表征。结果表明,复合粒子上的聚噻吩骨架中S原子与TiO2粒子间存在相互作用。以罗丹明B为模型降解物,研究了不同比例复合光催化剂在可见光下的光催化性能,其中m(Th)/m(Tb掺杂介孔TiO2)=1/10复合光催化剂光催化性能最好。在可见光照射下4 h,脱色率达到82.4%。这是由于Tb掺杂介孔TiO2与PTh(聚噻吩)之间的协同作用,拓宽了TiO2纳米粒子的光响应范围,提高了光生电子和空穴的分离效率,从而有效提高了其光催化性能。     

Oval cuboid TiO2 particles with mesoporous structure fabricated by using fluorinated block copolymers as templates with photocatalytic performance

In this work, a poly(ethylene glycol)-b-poly(1H,1H,7H-dodecafluoroheptyl methacrylate) (PEG-b-PDFMA) block copolymer was first synthesized by the reversible addition−fragmentation chain transfer (RAFT) polymerization. Then a novel facile approach was developed to fabricate oval cuboid TiO₂ particles with mesoporous structure by using the PEG-b-PDFMA block copolymer as a template and titanium tetrabutoxide (TBOT) as a precursor, followed by evaporation-induced self-assembly (EISA) process and calcination process. The results show that the PEG-b-PDFMA block copolymer can control the oriented assembly of nanoparticles and act as templates for the formation of a mesopore. It is found that the mass ratio of TBOT/PEG-b-PDFMA and water content in the solution have a significant influence on the morphology of TiO₂ particles. When the mass ratio of TBOT/PEG-b-PDFMA is 0.25/1, oval cuboid TiO₂ particles with mesopores are obtained, which exhibits a high photocatalytic activity for the degradation of methylene blue (MB) dye under UV light irradiation.     

Preparation of hollow TiO2 nanoparticles through TiO2 deposition on polystyrene latex particles and characterizations of their structure and photocatalytic activity

In a mixed solvent of water and ethanol, polystyrene/titanium dioxide (PSt/TiO₂) composite particles of core-shell structure were prepared by hydrolysis of tetrabutyl titanate in the presence of cationic PSt particles or anionic PSt particles surface-treated using γ-aminopropyl triethoxysilane. Hollow TiO₂ particles were obtained through calcination of the PSt/TiO₂ core-shell particles to burn off the PSt core or through dissolution of the core by tetrahydrofuran (THF). An alternative process constituted of preheating the PSt/TiO₂ particles at 200°C to allow partial crystallization followed by calcination or PSt dissolution by THF. The outcome TiO₂ particles thus prepared were examined by TEM, and hollow TiO₂ particles were observed. The crystalline phase structure and phase transformation were characterized, which revealed that preheating before the removal of the PSt core was useful to achieve the desired hollow TiO₂ particles, and the calcination process was beneficial to the formation of anatase and rutile structures. The tests of TiO₂ particles as catalyst in the photodegradation of Rhodamine B demonstrated that a much higher catalytic activity was observed with the TiO₂ hollow particles prepared through calcination combined with preheating.     

Studies on preparation and characterization of 3DOM TiO2 and TiO2/SiO2 materials with high photocatalytic ability

In this paper, three-dimensional ordered macroporous (3DOM) TiO₂ and TiO₂/SiO₂ materials were prepared by traditional colloidal-crystal-templating method. The microstructures of samples were analysed by scanning electron microscope, X-ray diffraction analysis, thermogravimetric-differential thermal analysis and nitrogen adsorption/desorption. The results indicated that the microstructures of samples, including three-dimensional ordered macroporous structure and crystalline form, could be adjusted by changing the calcination temperatures. Finally, the samples were used as photocatalysts to decompose methyl orange wastewater under UV-light. Both 3DOM TiO₂ and 3DOM TiO₂/SiO₂ displayed good photocatalytic ability. Moreover, the introduction of Si could increase the transformation temperature of TiO₂ from anatase to rutile, which made 3DOM TiO₂/SiO₂ had better photocatalytic ability than pure 3DOM TiO₂.