孔道三维相互连通锐钛矿TiO_2-SiO_2纳米复合介孔材料的制备及其高光催化活性（英文）

本文报道一种孔道三维相互连通锐钛矿TiO_2-SiO_2纳米复合介孔材料的制备.该介孔材料是以两维六方有序结构、直孔道、锐钛矿70TiO_2-30SiO_2-950纳米复合介孔材料(于950oC晶化2 h)为前驱体,NaOH为SiO_2的刻蚀剂,通过"在孔壁内造孔"的方法获得.我们的策略是采用温和的造孔条件,如稀NaOH溶液,合适的温度与固/液比等.采用X射线衍射(XRD),透射电镜(TEM)和低温N_2吸附等技术对样品的介孔结构进行了系统表征.结果表明,墙内孔的密度非常高,孔径均一(平均尺寸3.6 nm),且在三维网络高度连通原孔道,但介孔结构仍保持其完整性.锐钛矿纳米晶粒的结晶度和大小在墙内造孔前后基本保持不变.该材料光催化降解罗丹明B(0.303 min~(–1))与亚甲基蓝(0.757 min~(–1))的活性相当高,此活性分别是其母体材料的5.1和5.3倍,甚至是Degussa P25光催化剂的16.5和24.1倍.这充分表明三维连通孔道结构对活性的大幅提高起了关键作用.孔道三维连通式锐钛矿TiO_2-SiO_2纳米复合介孔材料对上述污染物展现出意想不到的高降解活性,显著高于迄今已报道的金属氧化物基介孔材料对上述污染物的降解活性.更重要的是,该光催化剂具有相当高的稳定性和重复使用性.相信,本方法将为具有超高性能的孔道三维相互连通其它金属氧化物基介孔材料的制备铺平了道路.小角XRD结果表明,母体材料的孔道是两维六方有序结构,在孔壁内造孔之后,样品原有的介孔结构仍保持其规整性.宽角XRD结果显示,二氧化钛的晶相是锐钛矿,晶粒尺寸为10.8 nm.造新孔之后,锐钛矿纳米晶粒的结晶度和大小与母体样品的相比变化不大.TEM结果显示,母体样品的孔壁内没有孔.孔道是两维六方有序排列的直孔道,孔径大小均一(平均尺寸4.1 nm).高分辨透射电镜(TEM)观察揭示,锐钛矿纳米晶粒(平均大小11.3 nm)在孔壁内随机排列,并与无定形SiO_2纳米颗粒相互连接,相间共存,形成类似"砖块-水泥砂浆"砌成的孔壁,这种独特的复合骨架结构赋予其很高的稳定性.当一些SiO_2纳米颗粒被去除之后,TEM观察显示,孔壁内有密集分布的孔,这些孔取向随机,并在三维方向连通原孔道,但介孔骨架结构仍保持其完整性.墙内孔的大小范围很窄(3.1-4.3 nm),平均大小为3.6 nm.高分辨TEM观察显示,锐钛矿晶粒大小与母体材料内的相比基本未变.上述结果与XRD结果一致.低温N_2吸附表征结果显示,母体样品内只有一种孔道,孔径为4.0 nm.去除部分SiO_2后的样品内有两种孔道,孔径分别是3.4和4.1 nm.这些结果与TEM的观察吻合.罗丹明B与亚甲基蓝在造孔前后样品内扩散速率评价结果显示,其在三维连通孔道内的扩散速率很高,大约是其母体材料内的5倍以上.这表明相互连通的孔道网络结构非常有利于客体分子在其内扩散.光催化降解性能评价结果显示,罗丹明B与亚甲基蓝在相互连通孔道内降解的速率相当高,分别是其在不连通孔道内的5.1和5.3倍.这充分证明孔道三维相互连通对活性的大幅提高起了关键作用.我们对材料的稳定性和重复使用性作了评价,经过10次循环使用孔道三维相互连通锐钛矿TiO_2-SiO_2纳米复合介孔材料,其吸附与光催化降解罗丹明B的性能变化不大.这充分证明本文制备的孔道连通复合介孔材料的性能是相当稳定的和可重复使用的.该方法可用于制备具有超高性能的孔道三维相互连通其它金属氧化物基介孔材料,如Nb_2O_5,Ta_2O_5等.     

纳米TiO_2-SnO_2介孔材料的制备及其对含氰废水的光催化降解性能

以TiCl4和SnCl4为原料,采用直接水解常压液相反应合成出了纳米TiO2-SnO2复合介孔材料.利用XRD和TEM及漫反射谱等对样品进行了表征,并研究了纳米TiO2-SnO2复合介孔材料对含氰废水的光催化降解性能.结果表明,纳米TiO2与SnO2复合后,导致材料的光谱响应拓宽;此种催化剂在日光灯下比在紫外灯下对废水中CN-的降解效果要好.     

三维有序介孔/大孔TiO2微球的制备、表征及光催化性能

以聚甲基丙烯酸甲酯微球为模板,分别以钛酸四丁酯和四异丙醇钛为钛源,通过溶胶-凝胶法辅助模板法制得TiO2纳米微球前驱体,并用程序升温控制其焙烧温度,最终成功制得了具有三维有序介孔/大孔复合结构的TiO2微球.以罗丹明B(RhB)为模型污染物,探索了以不同钛源制备得到的介孔/大孔复合TiO2微球的光催化性能;并采用XRD、SEM、TEM、UV-vis DRS、比表面积测试、光催化性能测试等对样品的晶粒尺寸、物相、形貌、光吸收、比表面积及性能等进行了分析.结果表明,运用溶胶凝胶法辅助模板法能够合成结晶度高、形貌规整、比表面积大、光催化活性良好的锐钛矿相TiO2微球.     

无序介孔硅复合纳米结构的制备与慢活化行为

通过对SiO_2纳米粒子进行镁热还原及后处理,制备了多级无序Si介孔复合纳米结构MP-Si@SiO_x@C,此结构展现出容量非衰减缓升的电化学慢活化行为,可抵消循环容量常规衰减趋势,赋予负极优良的循环稳定性.通过X射线衍射(XRD)、透射电子显微镜(TEM)、场发射扫描电子显微镜(SEM)、N_2吸附-脱附测试和孔径分布模拟分析发现,Si介孔组织包含微-窄介孔(1~5 nm)、中介孔(5~20 nm)以及大介孔-宏孔(20~100 nm)三级孔道,分别源于原初级粒子内部孔道、粒子团聚堆垛与粒内酸蚀、团聚体再堆垛;此合成装配方法有效提升了Si材料的堆积密度,电池电极能获得较高的体积比容量和储能密度.     

锐钛矿型纳米TiO2介孔粉体表面织构的研究

以硫酸钛和尿素为原料,聚乙二醇-1000为空间构造剂,104℃下经尿素水解均匀沉淀法研制颗粒分散均匀、粒径可控的高热稳定性锐钛矿型纳米TiO2介孔粉体,并对其晶相、颗粒大小、比表面积、形貌和孔道结构进行了表征.结果表明,未经任何热处理的TiO2粉体即为锐钛型晶相,颗粒为均匀分散的类球型颗粒,且颗粒间形成直通型的介孔孔道,其孔径在10～30nm之间.控制焙烧温度可以达到控制颗粒大小及形貌的目的,经850℃焙烧5h的样品仍保持锐钛矿型晶相,未出现向金红石型晶相转变的迹象.     

大孔-介孔氮掺杂二氧化钛的制备及其光催化性能测试

以嵌段共聚物为模板剂,甲酰胺为氮源,结合溶胶凝胶法制备了具有可见光活性的大孔-介孔氮掺杂二氧化钛(N-TiO2)材料.通过X射线衍射、低温N2吸附-脱附、扫描电镜、紫外-可见吸收光谱等手段,考察了嵌段共聚物对样品微结构和可见光活性的影响.结果表明,样品主要以锐钛矿相和板钛矿相混合形式存在;改变嵌段共聚物的浓度,可以制得晶粒粒径9～12 nm,孔径10～14 nm,禁带宽度2.98～2.76 eV的大孔-介孔N-TiO2,且随着模板剂加入量的增加,大孔孔径增大,孔壁增厚.对甲基橙溶液的室内自然光降解实验表明,大孔-介孔N-TiO2具有良好的光催化活性,随着嵌段共聚物加入量的增加,样品对甲基橙的降解时间缩短,降解率提高.     

氨基功能化有序介孔Si02薄膜组装Au纳米粒子复合材料的可调色散性质

以聚环氧乙烷-聚环氧丙烷-聚环氧乙烷(P123)为模板剂,采用共溶胶的蒸发诱导自组装方法制备了氨基功能化介孔SO2薄膜,然后利用氯金酸(HAUCl4)与介孔SiO2薄膜孔道内壁的氨基之间的中和反应组装Au纳米粒子,制备得到Au/SiO2纳米复合材料.用TEM,XRD和UV-Vis光谱对材料进行了测试.结果表明,无水乙醇...     

纳米Ni/SiO2介孔复合体的制备与超顺磁性

采用溶胶—凝胶法制备了含Ni2+的SiO2干凝胶,再通过化学还原得到了纳米Ni/SiO2介孔复合体。从样品的透射电子显微镜观测结果可估算出,介孔复合体中Ni粒子的尺寸约为11～12 nm。样品的磁性测量结果表明,与通常的Ni纳米颗粒相比,纳米Ni/SiO2介孔复合体中纳米Ni粒子的粒径在大于理论计算的纳米Ni粒子的临界尺寸时,仍能够保持超顺磁状态。在一定温度范围内,提高还原温度有利于复合体中纳米Ni粒子向超顺磁状态转变。     

TiO2介孔薄膜的制备及紫外光电响应性质

采用蒸发诱导自组装法制备了高度有序的TiO2介孔薄膜. 利用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等分析手段对其进行了表征. 结果表明, 所得样品的孔径约为5 nm, 孔道规则, 且骨架为纯锐钛矿结构. 紫外-可见光谱(UV-Vis)的表征结果表明, 制备的TiO2介孔薄膜对波长小于380 nm的紫外线有很强的吸收. 对TiO2介孔薄膜的I-V(电流-电压)特性进行了表征, 发现加光后其I-V曲线由暗态时的肖特基特性转变为欧姆特性, 表明TiO2介孔薄膜对紫外光有很敏感的光电响应.     

H_3PW_(12)O_(40)掺杂TiO_2介孔材料的制备及光催化性能

以P123为模板剂,采用溶胶-凝胶的溶剂热合成方法制备了H3PW12O40掺杂TiO2介孔材料H3PW12O40/TiO2.利用紫外可见漫反射吸收光谱(UV-vis/DRS)、X射线粉末衍射(XRD)、N2吸附和透射电子显微镜(TEM)手段对所制备的材料进行结构表征,罗丹明B(RB)为模型污染物评价其光催化性能.结果表明,所制备的介孔材料具有锐钛矿与板钛矿复合的晶型结构、大的BET比表面积和孔径均匀分布的介孔结构.光催化实验表明,H3PW12O40/TiO2可将罗丹明B完全矿化.     

Sb2O3／TiO2纳米复合物的合成及性质研究

以改进的溶胶-凝胶法制备了Sb2O3／TiO2纳米复合物,用扫描电镜、X射线粉末衍射、傅立叶红外光谱、紫外-可见光谱以及荧光等测试技术对产物进行了分析和表征．结果表明：所得纳米复合物颗粒分散均匀,具有锐钛矿相结构,平均粒径约为10nm．还研究了所得产物的光催化性质、电化学性质及电化学发光行为．结果表明：Sb2O3的掺入可以提高TiO2的光催化效果,当反应物中m（Sb2O3）／m（TiO2）=10％时,所得纳米复合物对亚甲基蓝和罗丹明B的光催化效果最好．     

Solid-solid interface formation in TiO2 nanoparticle networks

Aiming at a comparison of microstructure and paramagnetic properties of mesoporous TiO(2) nanoparticle networks, we subjected entirely different TiO(2-x) precursor structures to vacuum annealing. The transformation of an amorphous TiO(2-x) gel--obtained by sol-gel processing of an ethylene glycol-modified titanium precursor--into a network of interconnected anatase nanocrystals was explored by means of X-ray diffraction, nitrogen sorption, and electron microscopy. Crystalline junctions between the particles emerge from temperature treatment. This process of particle network formation is different from that related to the vapor phase grown anatase nanocrystals where particle-particle interface formation is induced by contact with water. It was found that, after annealing up to 873 K and controlled sample purification in oxygen atmosphere, both types of samples exhibit high concentrations of particle-particle interfaces and comparable properties in terms of surface area, porosity, and microstructure. With electron paramagnetic resonance (EPR) we observed on nonstoichiometric TiO(2-x) networks an identical type of subsurface defect which is related to the presence of solid-solid interfaces.     

块状TiO2/SiO2气凝胶的非超临界干燥法制备及其表征

分别通过TiO2和SiO2的单独溶胶和TiO2/SiO2复合凝胶,并添加干燥控制化学添加剂甲酰胺,形成比较完善的凝胶网络结构,同时通过正硅酸乙酯的乙醇溶液浸泡,低表面张力溶剂替换和分级陈化以及干燥等步骤,实现了块状TiO2/SiO2复合气凝胶的非超临界干燥制备.所得TiO2/SiO2气凝胶为无色或乳白色轻质块状多孔固体,表观密度约0.4～0.9g/cm3,孔隙率约80%～95%.它由直径约10nm的TiO2和SiO2微粒相互分散复合而成,孔洞直径约几十纳米.其相态SiO2为无定形,TiO2为锐钛矿晶型.随着焙烧温度的升高,直到800℃不发生相变化.     

A Stand-Alone Mesoporous Crystal Structure Model from in situ X-ray Diffraction: Nitrogen Adsorption on 3 D Cagelike Mesoporous Silica SBA-16

We present a modeling scheme to analyze cagelike silica mesoporous crystals based on in situ X-ray diffraction (XRD) data collected during gas adsorption-desorption (physisorption) processes. Nitrogen physisorption on a silica mesoporous crystal of SBA-16 was directly monitored by using synchrotron in situ powder XRD measurements conducted at SPring-8. SBA-16 is a well-ordered mesoporous silica in which three-dimensional interconnected cagelike primary mesopores are located at the body-centered cubic lattice points. In addition, the surrounding silica matrix contains random microporous and mesoporous intrawall porosities that are significantly influential to the diffusion properties, and thus important to be quantified for this media. The in situ XRD data exhibits seven Bragg reflections throughout the measurements, and the present method allows one to obtain the maximal and stand-alone information about the pore structure (for example, the mesopore size, the matrix density, the intrawall porosity, and pore surface roughness) together with the nitrogen film evolution in the primary mesopores and the intrawall pore-filling in the silica matrix. We furthermore observe a macroscopic amount of nitrogen adsorbed assuming the density of the fluid, and confirm that the XRD "isotherm" recalculated from the analysis result is consistent with the conventional nitrogen isotherm on a semi-quantitative level; however, these results suggest that the intrawall pores would have a greater contribution to the adsorption than considered based on the conventional isotherm analyses. The present method is readily extendable to any ordered mesopores wrapped by the wall matrix containing a certain intrawall porosity.     

微乳法合成纳米SiO2/TiO2及其光催化性能

采用聚乙二醇辛基苯基醚(Triton X-100)/正己醇/环己烷/氨水微乳体系合成了纳米TiO2和SiO2/TiO2复合物,用X射线衍射、红外光谱和透射电镜对其结构进行了表征,并以甲基橙降解评价了其光催化性能,讨论了SiO2/TiO2摩尔比、晶相组成及粒径与光催化活性的关系.结果表明,SiO2/TiO2催化剂中形成了新的Ti-O-Si键和无定形SiO2;在纳米TiO2中复合SiO2能有效抑制锐钛矿向金红石的转变,增加锐钛矿的稳定性,并阻止TiO2晶粒的聚集生长.催化剂的光催化活性随金红石含量的增加而降低,加入适量SiO2能明显提高TiO2的光催化活性,其中摩尔比为1/7的SiO2/TiO2光催化活性最高.     

Encapsulating Sulfur into Hierarchically Ordered Porous Carbon as a High‐Performance Cathode for Lithium–Sulfur Batteries

A three‐dimensional (3D) hierarchical carbon–sulfur nanocomposite that is useful as a high‐performance cathode for rechargeable lithium–sulfur batteries is reported. The 3D hierarchically ordered porous carbon (HOPC) with mesoporous walls and interconnected macropores was prepared by in situ self‐assembly of colloidal polymer and silica spheres with sucrose as the carbon source. The obtained porous carbon possesses a large specific surface area and pore volume with narrow mesopore size distribution, and acts as a host and conducting framework to contain highly dispersed elemental sulfur. Electrochemical tests reveal that the HOPC/S nanocomposite with well‐defined nanostructure delivers a high initial specific capacity up to 1193 mAh g^?1 and a stable capacity of 884 mAh g^?1 after 50 cycles at 0.1 C. In addition, the HOPC/S nanocomposite exhibits high reversible capacity at high rates. The excellent electrochemical performance is attributed exclusively to the beneficial integration of the mesopores for the electrochemical reaction and macropores for ion transport. The mesoporous walls of the HOPC act as solvent‐restricted reactors for the redox reaction of sulfur and aid in suppressing the diffusion of polysulfide species into the electrolyte. The “open” ordered interconnected macropores and windows facilitate transportation of electrolyte and solvated lithium ions during the charge/discharge process. These results show that nanostructured carbon with hierarchical pore distribution could be a promising scaffold for encapsulating sulfur to approach high specific capacity and energy density with long cycling performance.     

以花瓣为模板制备TiO2分层介孔纳米片

以月季花花瓣为模板, 经钛盐溶液浸渍后煅烧, 合成了新型TiO2 分层介孔纳米片. 采用X射线衍射(XRD)、 场发射扫描电子显微镜(FESEM)、 环境扫描电子显微镜(ESEM)、 透射电子显微镜(TEM)、 紫外-可见漫反射光谱(UV-Vis/DRS)和氮气吸附-脱附曲线分析等手段对样品进行了表征. 结果表明, 所得样品由厚度约4 nm的具有生物形态结构的锐钛矿型TiO2 纳米片组成. TiO2 薄层表面存在大量介孔, 其孔径集中分布于4 nm左右. 由紫外-可见漫反射吸收光谱可知, 材料的吸收边较纳米TiO2 (P25)红移了约20 nm, 因而具有更高的可见光光催化活性. TiO2 分层介孔纳米片在阳光下表现出较强的光催化活性, 在90 min内对亚甲基蓝的降解率可达98%, 远高于TiO2 纳米粉.     

Synthesis of biomorphological mesoporous TiO2 templated by mimicking bamboo membrane in supercritical CO2

A new approach is presented for preparing biomorphological mesoporous TiO2 templated by mimicking bamboo inner shell membrane via supercritical CO2 (SCCO2) transportation through titanium tetrabutyloxide (TTBO). The analysis of wide-angle X-ray powder diffraction (XRD) showed the prepared TiO2 in phase of anatase, and the small-angle XRD revealed the presence of mesopores without periodicity. The product exhibited the shape of crinkled films and extended in two dimensions up to centimeters. The electron microscopic observation showed that the TiO2 films were around 200 nm in thickness, and across the films there were numerous round or ellipse-shaped mesopores, being 10-50 nm in diameter, which were formed by the close packing of TiO2 particles. High-resolution transmission electron microscope (HRTEM) displayed that the single TiO2 particle size was about 12.5 nm. The UV-vis absorption spectrum was transparent in the wavelength of 320-350 nm for suspensions of the prepared mesoporous TiO2 in ethanol at the concentration of 5.0 mg/l. The mesoporous TiO2 prepared with the aid of SCCO2 exhibited an obvious blue shift compared with the TiO2 prepared by sol-gel infiltration. The possible mechanism for the formation of the mesoporous TiO2 is summarized into a biomimetic mineralization pathway. First, TTBO was transported to the membrane surface via SCCO2, and then condensed. Hydrolysis reactions between the functional groups of organic membrane and TTBO took place to form the nuclear TiO2, and the TiO2 seeds grew around the organic membrane into TiO2 mesoporous materials. The approach provides a low-cost and efficient route for the production of ceramics nanomaterials with unique structural features, which may have potential application in designing UV-selective shielding devices [S. Zhao, X.H. Wang, S.B. Xin, Q. Jiang, X.P. Liang, Rare Metal Mater. Eng. 35 (2006) 508-510].     

微米级大孔结构二氧化钛的光催化活性

以溶胶-凝胶法合成了具有微米级大孔孔道结构的锐钛矿晶型TiO₂, 以紫外光催化降解染料罗丹明B (RhB)考察了大孔结构材料的光催化活性. 对比研磨粉碎后失去大孔结构的材料的光催化活性, 我们发现在相同的实验条件下, 大孔结构的TiO₂并不具有更好的光催化效果, 即对于本文所合成的大孔结构TiO₂, 单纯的微米级大孔的形貌对材料的光催化活性没有明显的促进作用, 而更多的TiO₂外表面受到紫外光照射是促进光催化效果的直接原因. 由于研磨后样品颗粒尺寸不均匀, 为了避免颗粒大小不均匀对光催化活性的影响, 我们又用十六烷基三甲基溴化铵(CTAB)和聚丙烯酸(PAA)为模板合成了形貌均匀尺寸不同的微球, 并证明了粒子尺寸越小催化效果越好.     

Characterization of Pore Structure and Coordination of Titanium in TiO(2) and SiO(2)-TiO(2) Sol-Pillared Clays

Titania sol-pillared clay (TiO(2) PILC) and silica-titania sol-pillared clay (SiO(2)-TiO(2) PILC) were synthesized by the sol-gel method. Supercritical drying (SCD) and treatment with quaternary ammonium surfactants were used to tailor the pore structure of the resulting clay. It was found that SCD approach increased the external surface area of the PILCs dramatically and that treatment with surfactants could be used to tailor pore size because the mesopore formation in the galleries between the clay layers follows the templating mechanism as observed in the synthesis of MCM-41 materials. Highly mesoporous solids were thus obtained. In calcined TiO(2) PILC, ultrafine crystallites in anatase phase, which are active for photocatalytic oxidation of organics, were observed. In SiO(2)-TiO(2) PILCs and their derivatives, titanium was highly dispersed in the matrix of silica and no crystal phase was observed. The highly dispersed titanium sites are good catalytic centers for selective oxidation of organic compounds. Copyright 2001 Academic Press.