Triconstituent co-assembly to ordered mesostructured polymer-silica and carbon-silica nanocomposites and large-pore mesoporous carbons with high surface areas

Highly ordered mesoporous polymer-silica and carbon-silica nanocomposites with interpenetrating networks have been successfully synthesized by the evaporation-induced triconstituent co-assembly method, wherein soluble resol polymer is used as an organic precursor, prehydrolyzed TEOS is used as an inorganic precursor, and triblock copolymer F127 is used as a template. It is proposed for the first time that ordered mesoporous nanocomposites have "reinforced concrete"-structured frameworks. By adjusting the initial mass ratios of TEOS to resol, we determined the obtained nanocomposites possess continuous composition with the ratios ranging from zero to infinity for the two constituents that are "homogeneously" dispersed inside the pore walls. The presence of silicates in nanocomposites dramatically inhibits framework shrinkage during the calcination, resulting in highly ordered large-pore mesoporous carbon-silica nanocomposites. Combustion in air or etching in HF solution can remove carbon or silica from the carbon-silica nanocomposites and yield ordered mesoporous pure silica or carbon frameworks. The process generates plenty of small pores in carbon or/and silica pore walls. Ordered mesoporous carbons can then be obtained with large pore sizes of approximately 6.7 nm, pore volumes of approximately 2.0 cm(3)/g, and high surface areas of approximately 2470 m(2)/g. The pore structures and textures can be controlled by varying the sizes and polymerization degrees of two constituent precursors. Accordingly, by simply tuning the aging time of TEOS, ordered mesoporous carbons with evident bimodal pores at 2.6 and 5.8 nm can be synthesized.     

孔道三维相互连通锐钛矿TiO2-SiO2纳米复合介孔材料的制备及其高光催化活性

本文报道一种孔道三维相互连通锐钛矿TiO2-SiO2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70TiO2-30SiO2-950纳米复合介孔材料(于950oC晶化2 h)为前驱体, NaOH为SiO2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N2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TiO2-SiO2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SiO2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SiO2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N2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SiO2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TiO2-SiO2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Nb2O5, Ta2O5等.     

介孔TiO2的水热法制备及其光催化性能

以二钛酸钾(K2Ti2O5)经离子交换得到的无定形水合二钛酸(H2Ti2O5·xH2O)为原料, 与葡萄糖溶液在220 ℃下进行水热反应, 再在空气中520 ℃焙烧, 制备出介孔TiO2. 用扫描电子显微镜(SEM)、X射线衍射(XRD)、N2吸附、透射电子显微镜(TEM)等技术对样品进行了表征. 结果表明, 该介孔TiO2具有微米级棒状或针状形貌, 晶粒大小为12.3 nm, 比表面积为106 m2·g-1, 孔容为0.31 cm3·g-1, 孔径为8.06 nm, 焙烧处理后晶型仍是锐钛矿相. 水热生成的碳抑制了晶粒的团聚生长和晶型的转变, 提高了介孔TiO2的热稳定性. 甲基橙降解实验评价了介孔TiO2的光催化性能, 结果发现其活性与商用TiO2催化剂P25相当, 而其较大的粒径更容易回收再利用. 以碘化钾为探针反应, 表明介孔TiO2的光催化机制以光生空穴氧化为主.     

SO42-/TiO2-SiO2的制备及对甲基橙的光催化降解

0 引言 水中难降解有机物的治理已成为当今重要的环境问题,对新型高效水处理剂的需求也愈加迫切。多相光催化氧化已成为国内外治理污水的新技术,但常规二氧化钛半导体光催化剂的量子效率     

多金属氧酸盐/TiO2介孔杂化材料的合成及光催化性能研究

采用蒸发诱导自组装法合成了介孔TiO2,并将表面含有Si-OH基团的钨磷酸盐衍生物(Bu4N)3PW11O39-[O(SiOH)2](TBAPW11Si2)嫁接到乙醇回流脱模的介孔TiO2上,合成了TBAPW11Si2/TiO2介孔杂化材料.采用IR、XRD、N2吸附-脱附、TEM、ICP-AES对样品的结构和组成进行了表征.结果表明,TBAPW11Si2与TiO2之间的共价键联是通过表面Si-OH和Ti-OH间的缩合进行的;TiO2表面足够的Ti-OH基团和一定温度的焙烧是这一缩合的必要条件.与TiO2载体相比,嫁接了TBAPW11Si2的杂化样品,锐钛矿相的结晶度略有增加;但表面积、孔容和孔径均有所减小,且随TBAPW11Si2负载量的增加而降低.光催化降解甲基橙的结果显示,杂化样品表现出比载体TiO2高得多的催化活性,甚至与高结晶度的商品光催化剂P25相当,显示出多金属氧酸盐-TiO2协同作用的优越性.     

Enhanced photocatalytic degradation of C.I. Basic Violet 2 using TiO2-SiO2 composite nanoparticles

In this report, TiO(2) -SiO(2) composite nanoparticles were prepared by the thermal hydrolysis method using titanium tetrachloride and tetraethylorthosilicate as TiO(2) and SiO(2) precursors, respectively. The prepared nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption/desorption and UV-Vis diffuse reflectance spectroscopy (DRS). The results indicated that, in comparison with pure TiO(2), TiO(2)-SiO(2) composite nanoparticles had a higher thermal stability, which prevents phase transformation from anatase to rutile. In addition, the TiO(2)-SiO(2) nanoparticles had a higher specific surface area, larger pore volume, greater band gap energy and smaller crystallite size. Thus, the surface area of TiO(2)-40% SiO(2) composite nanoparticles was about 17 times higher than that of pure TiO(2) nanoparticles. The photocatalytic activity of TiO(2)-SiO(2) composite nanoparticles in the photodegradation of C.I. Basic Violet 2 was investigated. The photodegradation rate of Basic Violet 2 using TiO(2)-40% SiO(2) nanoparticles calcined at 600°C was much faster than that using pure TiO(2) and Degussa P25 TiO(2) by 10.9 and 4.3 times, respectively. The higher photoactivity of the TiO(2)-SiO(2) composite nanoparticles was attributed to their higher surface area, larger pore volume, greater band-gap energy and smaller crystallite size compared with pure TiO(2).     

Properties of TiO2-SiO2 Mixed Oxides and Photocatalytic Oxidation of Heptane and Sulfur Dioxide

A series of TiO2-XSiO2[X denotes the molar fraction(%) of silica in the mixed oxides] with different n(Ti)/n(Si) ratios was prepared with ammonia water as a hydrolysis catalyst. The photocatalysts prepared were characterized by XRD, thermal analysis, FTIR, UV-Vis and SPS. The characterization results of FTIR and UV-Vis spectra show that Ti atoms were gradually changed from octahedral coordination to tetrahedral coordination with the addition of silica, which is not beneficial for obtaining strong Bronsted acidity and higher photocatalytic activity. The photocatalytic activity experiments, which were conducted by using heptane (or SO2) as the model reactant, showed that TiO2-SiO2 containing a suitable amount of silica can exhibit much higher photocataiytic activity than pure TiO2. The enhanced photocatalytic activity can be attributed tothree following factors.. (1) smaller crystalline size;(2) higher thermal stability; (3) the new strong Broensted acidity.     

TiO2 nanoparticles in mesoporous TUD-1: synthesis, characterization and photocatalytic performance in propane oxidation

A series of TiO2-TUD-1 samples was synthesized with a variable Ti loading in the range Si/Ti = 100, 20, 2.5, and 1.6, by using a one-pot surfactant-free procedure. The materials obtained were characterized by elemental analysis; X-ray diffraction (XRD); N2 sorption measurements; high-resolution TEM (HR-TEM); 29Si NMR, UV-visible and Raman spectroscopy. As a function of increasing metal loading either isolated Ti atoms, or (above a Ti loading of approximately 2.5 wt- %) combinations of isolated Ti atoms and anatase (TiO2) nanoparticles were obtained; both were incorporated in the highly porous siliceous matrix. The photocatalytic performance of these materials was tested by studying the propane oxidation process following irradiation at lambda = 365 nm, selectively activating the anatase nanoparticles. In comparison to commercial anatase powder, TiO2 nanoparticles in TUD-1 showed high photochemical selectivity towards acetone, the sample with a Si/Ti ratio of 1.6 being the most selective. Size and confinement effects are consistent with the difference in performance of the TUD-1 materials and TiO2, limiting the number of electron transfers available for each propane molecule.     

纳米TiO2-SiO2复合氧化物的制备与性质

采用溶胶-凝胶结合CO2超临界干燥方法制备了比表面积大、热稳定性好的纳米TiO2-SiO2复合氧化物.考察了原料组成和焙烧温度对复合氧化物比表面积、热稳定性和酸性的影响,通过加氢脱硫反应考察了该复合氧化物作为加氢精制催化剂载体的可行性.结果表明,采用该方法制备的复合氧化物为纳米颗粒,在n(Ti)/n(Si)=1时,其比表面积和孔容最大;与纯TiO2相比,引入SiO2明显提高了复合氧化物的热稳定性和晶型稳定性;以此复合氧化物为载体的加氢精制催化剂具有很好的低温脱硫活性,TiO2-SiO2复合氧化物载体的酸性特征影响了催化剂的加氢脱硫活性.     

低温水热法制备硅胶负载型二氧化钛催化剂

TiO2作为一种优良的光催化材料,能够降解有机物,起到抗菌防污的作用,其在工业上的潜在应用已吸引众多研究者的普遍关注和深入研究[1-3]。为了进一步提高它的光催化活性,研究者试图运用各种方法和技术对纯TiO2进行改进。负载[3]是其中常用方法之一。对于无负载的二氧化钛,由于本     

以混合表面活性剂为模板可控合成MCM-48和MCM-41分子筛

利用阳离子和三嵌段共聚物混合表面活性剂为模板,在水热条件、碱性介质中可控合成出MCM-48和MCM-41分子筛。在固定P123(聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物):TEOS(正硅酸乙酯)(物质的量的比)为0.01875的体系中,调节CTAB(十六烷基三甲基溴化铵)∶TEOS(正硅酸乙酯)物质的量比值m,当m在0.12~0.13范围合成出MCM-48分子筛;当m在0.04~0.08范围合成出MCM-41分子筛。通过XRD,TEM,N2物理吸附,IR等方法进行了表征。结果表明:聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物(P123)的加入可以更大程度地降低合成介孔材料所需阳离子表面活性剂的用量;可控合成的介孔材料具有高比表面积、高度有序的孔道结构、较集中的孔径分布。     

One-pot synthesis of highly crystalline mesoporous TiO2 nanoparticle assemblies with enhanced photocatalytic activity

We report an unprecedented formation of mesoporous titania via a surfactant-assisted aggregating assembly of TiO(2) nanoparticles. These mesostructures possess a highly crystalline anatase phase, large and accessible pore surface area, and exhibit superior photocatalytic performance.     

溶胶-凝胶-水热法制备Ce-Si/TiO2及其可见光催化性能

以钛酸四正丁酯、正硅酸乙酯、六水硝酸铈为原料, 在140 ℃下通过溶胶-凝胶-水热法水解制备Ce-Si/TiO2. 所得样品用X射线衍射、氮吸附、透射电镜、紫外漫反射、傅里叶变换红外光谱、X射线光电子能谱等测试手段分析, 结果显示400-600 ℃条件下焙烧所有样品均为锐钛矿, 样品具有较大的比表面积, Si和Ce均被引入到TiO2中. 在可见光照射下, 以脱色降解罗丹明B为探针反应, 研究其可见光催化性能, 结果表明, 与未掺杂和单一组分掺杂的二氧化钛相比较, 共掺杂的二氧化钛具有更高的催化性能, 当Ce/Ti和Si/Ti的物质的量比分别为0.010和0.10时,可见光催化性能最好.     

Photocatalytic Degradation of Acetaldehyde on Mesoporous TiO2: E?ects of Surface Area and Crystallinity on the Photocatalytic Activity

"Mesoporous TiO2 powder and films with worm-like channels were synthesized by an evaporation-induced self-assembly approach. The as-prepared samples were calcined at different temperature to investigate the effect of calcined temperature on the mesostructure and the photocatalytic activity. Acetaldehyde photodegradation in gas phase was employed to evaluate the photocatalytic activity of mesoporous TiO2. Results showed that all the calcined powder samples exhibited higher photocatalytic activities than that of Degussa P25. The sample calcined at 400 oC, which showed higher activity than other samples, possessed a homogeneous pore diameter of about 6.0 nm and an 11.0 nm crystalline anatase pore wall, as well as large surface area of 117 m2/g. It was speculated that two factors of surface area and crystallinity affected the photocatalytic activity of mesoporous TiO2 photocatalyst. The mesoporous TiO2 films fabricated by spin-coating also had high photocatalytic activities."     

Ti3C2 MXene助催化剂组装的介孔TiO2用以增强光催化甲基橙降解和产氢活性

利用太阳能驱动半导体光催化剂进行光催化降解污染物和产氢被认为是解决环境问题和能源危机最有效的方法之一.在众多的半导体光催化剂中,TiO₂因其优异的化学稳定性、环境友好和成本低等优点,在光催化领域具有不可或缺的作用.介孔TiO₂由于具有独特的介孔结构,更有利于光催化过程中反应物的吸附和传输.然而,单一TiO₂具有较高的光生载流子重组效率和低的光利用率等缺点,导致其光催化活性低.通过负载助催化剂可以增强光吸收、促进光生载流子的分离以及提供更多活性位点,是提高光催化活性的一种有效策略.目前,常用的高效助催化剂主要为贵金属,如Pt,Pd和Au等,但昂贵的价格及稀缺性限制了其在未来的广泛应用.因此,寻找新型的非贵金属助催化剂来提高光催化剂的活性具有重要意义.MXene作为一种新型的二维过渡金属碳化物和/或氮化物,具有丰富的表面亲水性官能团、良好的金属导电性和较高的载流子迁移率等特性,适合用于光催化中作为助催化剂来提高光催化性能.受此启发,本文利用静电自组装策略将介孔TiO₂纳米颗粒均匀地固定在Ti₃C₂MXene助催化剂上,构建了紧密的介孔TiO₂/Ti₃C₂复合材料,并研究其光催化降解甲基橙(MO)和产氢性能.Zeta电位测试结果表明,带有相反表面电荷的介孔TiO₂和Ti₃C₂可以通过静电作用构筑稳定的复合材料.X-射线粉末衍射、拉曼光谱、X-射线光电子能谱(XPS)、透射电子显微镜和高分辨透射电子显微镜等表征也进一步表明,成功制备了介孔TiO₂/Ti₃C₂复合材料.XPS也证明在复合材料中光生电子从TiO₂转移到Ti₃C₂助催化剂上,表明两者之间具有强相互作用.BET测试结果表明,相比单一的介孔TiO₂,复合材料具有更大的比表面积和孔体积,可提供更多的活性位点,有利于提高光催化活性.紫外-可见漫反射光谱表明,Ti₃C₂助催化剂的引入提高了材料的光吸收能力.荧光光谱、时间分辨荧光光谱、光电流密度和电化学阻抗等测试结果表明,复合材料具有优异的光生载流子分离和转移能力.在光催化性能测试中,最佳Ti₃C₂含量(3wt%)的介孔TiO₂/Ti₃C₂复合材料在40 min内对MO的光催化降解效率可达99.6%,并利用自由基捕获实验和电子自旋共振表征证实了活性物种·O₂-和·OH在光催化降解过程中起主要作用.此外,该复合材料也表现出了较好的产氢性能(218.85μmolg^-1h^-1),约为单一介孔TiO₂的5.6倍,且三次循环后仍保持稳定的产氢效率.综上,MXene族材料可以作为一种高效的非贵金属助催化剂应用于光催化领域.     

共价键联的PW11/TiO2介孔杂化材料的合成及其光催化性能

采用二次嫁接的方法,将Keggin结构的缺位钨磷酸盐PW11嫁接到介孔TiO2的表面,得到PW11/TiO2杂化样品。采用IR、低温N2吸附、XRD、TEM和ICP-AES等对样品的结构、PW11负载量以及键联机理进行了表征和研究,对样品光催化降解甲基橙的性能进行了考察。 结果显示,用蒸发诱导自组装法合成的TiO2,焙烧前结构松散,可部分水解并与PW11反应,生成PW11Ti物种,后者与TiO2骨架缩合,从而实现PW11的键联嫁接。 与纯TiO2相比,杂化样品中锐钛矿相的结晶度稍有降低,孔径、孔容减小,但是对甲基橙的光催化降解活性却明显增加,显然这是PW11和TiO2间发生了“协同效应”所致。     

Si掺杂TiO2纤维的溶胶-凝胶法制备及其光催化活性

采用溶胶-凝胶法并结合水蒸气活化制备了Si掺杂TiO₂纤维, 通过TG-DSC, XRD, FT-IR, UV-Vis-DRS, N₂吸附-脱附, SEM等手段对纤维样品的结构参数及其表面形貌进行了表征, 并以活性艳红X-3B模拟废水体系评价了其光催化活性．结果表明, 与纯TiO₂产物相比, 适量Si掺杂制得的产物是具有丰富介孔结构的TiO₂长纤维, 不仅热稳定性和晶型稳定性俱佳, 而且光催化活性得以显著提高, 经900 ℃热处理后仍能保持结晶完好的锐钛矿相; 在Si/Ti摩尔比为0.15时, 其比表面积和孔容最大, 光催化活性最佳, 该纤维作为光催化剂反应75 min, 水中X-3B的降解率可达99.6%.     

Sodium niobate adsorbents doped with tantalum (TaV) for the removal of bivalent radioactive ions in waste waters

Mesoporous silica containing a large amount of isolated Ti was prepared from an alkoxytitanosiloxane precursor through a hard template method. Isopropoxytris(tris-tert-butoxysiloxy)titanium (((i)PrO)Ti[OSi(O(t)Bu)(3)](3), TS3) was synthesized and TS3 was mixed with mesoporous carbon (CMK-3), a hard template. The mixture was pyrolyzed at 180 °C to form a composite consisting of titanosilica and the hard template. After calcination at 600 °C for the removal of the carbon template, the titanium species were not transformed to anatase TiO(2), proved by DR-UV-Vis, FTIR, XPS, and XRD, while the ESR results indicated the presence of isolated Ti. The mesoporous structure was verified by SEM, TEM, and N(2) adsorption. The Si/Ti ratio of the product was consistent with that of the precursor. All the results show that the material prepared from the precursor is ordered mesoporous silica containing a large amount of isolated Ti in the frameworks. The use of well-defined alkoxytitanosiloxane precursor leads to the formation of mesoporous silica with exactly controlled composition of titanium with neither loss of Ti nor transformation to anatase.     

Synthesis of titanium dioxide nanoparticles with mesoporous anatase wall and high photocatalytic activity

Mesoporous titanium dioxide nanosized powder with high specific surface area and anatase wall was synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting materials were characterized by XRD, nitrogen adsorption, FESEM, TEM, and FT-IR spectroscopy. The as-synthesized mesoporous TiO2 nanoparticles have mean diameter of 17.6 nm with mean pore size of 2.1 nm. The specific surface area of the as-synthesized mesoporous nanosized TiO2 exceeded 430 m2/g and that of the samples after calcination at 600 degrees C still have 221.9 m2/g. The mesoporous TiO2 nanoparticles show significant activities on the oxidation of Rhodamine B (RB). The large surface area, small crystalline size, and well-crystallized anatase mesostructure can explain the high photocatalytic activity of mesoporous TiO2 nanoparticles calcined at 400 degrees C.     

碳纳米管负载纳米TiO2复合材料的制备及其性能

采用溶胶-凝胶法, 以钛酸丁酯为原料, 将纳米TiO2负载在碳纳米管(CNTs)表面, 制备了CNT-TiO2光催化复合材料. 通过X射线衍射(XRD)、透射电子显微镜(TEM)等手段研究了复合颗粒的形态结构及包覆情况, 通过UV-Vis漫反射谱分析比较了纯TiO2和CNT-TiO2的吸光性能, 并研究了不同温度热处理的CNT-TiO2光催化剂在紫外光照射下对甲基橙光催化降解的性能. 结果表明, 纳米TiO2颗粒以锐钛矿相存在, 紧密地包附在碳纳米管的管壁上, CNT-TiO2在紫外-可见光波长范围内均有较好的吸光性能, 450 ℃热处理后的复合光催化剂CNT-TiO2比纯TiO2对甲基橙光降解有更高的光催化活性.