TiO2/Au纳米棒阵列的制备及其光催化性能

采用电沉积和旋转涂膜相结合的方法成功制备了高度有序的TiO2/Au纳米棒阵列催化剂.扫描电镜和透射电镜结果表明,TiO2薄膜均匀地包覆在Au纳米棒的表面,形成核壳型的一维阵列结构.X射线衍射分析表明所获得TiO2为(101)晶面优先生长的锐钛矿晶相.紫外-可见漫反射光谱显示,由于Au和TiO2间肖特基结的存在造成吸收红...     

Synthesis and characterization of ultrahigh crystalline TiO2 nanotubes

Ultrahigh crystalline TiO2 nanotubes were synthesized by hydrogen peroxide treatment of very low crystalline titania nanotubes (TiNT-as prepared), which were prepared with synthesized TiO2 nanoparticles by hydrothermal methods in an aqueous NaOH solution. Thus, prepared ultrahigh crystalline TiO2 nanotubes (TiNT-H2O2) showed comparable crystallinity with high crystalline TiO2 nanoparticles. The details of nanotubular structures were elucidated by high resolution-transmission electron microscopy (HR-TEM), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis in transmission electron microscopy (TEM-EDX), X-ray diffraction (XRD), photoluminescence (PL), and BET surface area. TiNT-H2O2 was found to be a multiwalled anatase phase only with an average outer diameter of approximately 8 nm and an inner diameter of approximately 5 nm and grown along the [001] direction to 500-700 nm long with an interlayer fringe distance of ca. 0.78 nm. The photocatalytic activity of TiNT-H2O2 was about 2-fold higher than those of TiNT-as prepared, synthesized TiO2 nanoparticles, and TiO2-P25 (Degussa) in the photocatalytic oxidation of trimethylamine gas under UV irradiation.     

Simultaneous phase- and size-controlled synthesis of TiO(2) nanorods via non-hydrolytic sol-gel reaction of syringe pump delivered precursors

The simultaneous phase- and size-controlled synthesis of TiO(2) nanorods was achieved via the non-hydrolytic sol-gel reaction of continuously delivered two titanium precursors using two separate syringe pumps. As the injection rate was decreased, the length of the TiO(2) nanorods was increased and their crystalline phase was simultaneously transformed from anatase to rutile. When the reaction was performed by injecting titanium precursors contained in two separate syringes into a hot oleylamine surfactant solution with an injection rate of 30 mL/h, anatase TiO(2) nanorods with dimensions of 6 nm (thickness) x 50 nm (length) were produced. When the injection rate was decreased to 2.5 mL/h, star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 200 nm and a small fraction of rod-shaped anatase TiO(2) nanorods with dimensions of 9 nm x 100 nm were synthesized. Pure star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 450 nm were synthesized when the injection rate was further decreased to 1.25 mL/h. The simultaneous phase transformation and length elongation of the TiO(2) nanorods were achieved. Under optimized reaction conditions, as much as 3.5 g of TiO(2) nanorods were produced. The TiO(2) nanorods were used to produce dye-sensitized solar cells, and the photoconversion efficiency of the mixture composed of star-shaped rutile TiO(2) nanorods and a small fraction of anatase nanorods were comparable to that of Degussa P-25.     

高纯纳米氧化钛的制备及催化活性

以工业级硫酸钛为原料,在酸性环境下以EDTA作为络合剂,采用控制沉淀法制备高纯度纳米TiO2。考察了pH值、反应温度、煅烧温度等工艺条件对TiO2颗粒晶型、大小和分布影响。利用TEM、XRD、ICP等手段对产物进行表征,TiO2纯度超过99.9%,粒径为10-20nm,分布均匀。经过对其光催化降解苯酚反应活性实验,结果表明样品具有较好的光催化活性。     

透明TiO2纳米管/FTO电极制备及表征

采用射频磁控溅射方法在透明导电玻璃(FTO)上沉积纯钛薄膜, 室温条件下在H3PO4+HF电解液中通过恒压阳极氧化方法得到TiO2纳米管阵列, 并通过场发射扫描电子显微镜(FESEM)、X射线衍射(XRD)、UV-Vis透射光谱以及光电化学的方法对纳米管阵列进行了表征. 研究表明, 在电压为20 V、氧化时间为50 min时, 钛薄膜转化为TiO2纳米管阵列, 管长约为380 nm, 内径约为90 nm, 管壁约为15 nm; 再经过500 ℃空气热处理6 h之后得到锐钛矿型的TiO2纳米管/FTO透明电极, 在可见光区的平均透过率约为80%, TiO2禁带宽度为3.28 eV, 发生了蓝移, 带尾扩展到2.6 eV; 此外, 对结晶前后的复合电极分别在暗态和紫外光下进行线性扫描和瞬态光电流测试, 结果表明, 结晶的电极表现出更好的光电转换性能; 施加阳极电压和紫外光照射都能够促进TiO2光生载流子有效分离,使电子迅速传至导电玻璃表面通过外电路形成光电流.     

One-step solvothermal synthesis of N-doped TiO2 nanoparticles with high photocatalytic activity in the reduction of aqueous Cr（Ⅵ）

N-doped TiO2 （N-TiO2） nanoparticles were synthesized via a one-step low temperature （180℃） solvothermal route, which adopted NH4NO3 as the nitrogen source. The structure, composition, BET specific surface area, and optical properties of the as-synthesized product were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption- desorption isotherms, and UV-vis diffuse reflectance spectroscopy. In addition, its photocatalytic properties were tested by the reduction of aqueous Cr（VI） under UV and visible light （x 〉 420 rim） irradiation. It was observed that for the reduction of aqueous Cr（VI）, the as-synthesized N-TiO2 nanoparticles not only exhibited much higher photocatalytic activity than P25 TiO2 under UV light, but also exhibited remarkably high photocatalytic activity under visible light （λ 〉 420 nm）.     

Electrospun nanofibers of TiO2/CdS heteroarchitectures with enhanced photocatalytic activity by visible light

Herein, we have demonstrated that the electrospun nanofibers of TiO(2)/CdS heteroarchitectures could be fabricated through combining electrospinning technique with hydrothermal process. The configuration, crystal structure, and element composition of the as-prepared TiO(2)/CdS heteroarchitectures were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), resonant Raman spectrometer, X-ray photoelectron spectroscopy (XPS). The results indicated that the high-density hexagonal wurtzite CdS crystalline particles of ca. 6-40 nm in diameter were uniformly and closely grown on anatase TiO(2) nanofibers. Especially, the light-absorption properties as well as photocatalytic characteristics of pure TiO(2) nanofibers and TiO(2)/CdS heteroarchitectures with different amount loading of CdS were also investigated. The absorption of TiO(2)/CdS heteroarchitectures was extended to the visible due to effective immobilization of sensitizing agent CdS on TiO(2). In contrast with the pure TiO(2) nanofibers, the TiO(2)/CdS heteroarchitectures showed excellent photocatalytic activity by using rhodamine B dye as a model organic substrate under visible-light irradiation. It was worth noting that the cooperative photocatalytic mechanism of the TiO(2)/CdS heteroarchitectures was also discussed.     

Synthesis and photocatalytic activity of TiO2 nanoparticles prepared by chemical vapor condensation method with different precursor concentration and residence time

Nanosized TiO(2) photocatalysts were synthesized using a chemical vapor condensation method under a range of synthesis conditions (precursor vapor concentration and residence time in a tubular electric furnace). X-ray diffraction showed that the prepared TiO(2) powders consisted mainly of anatase (>94%) with a small amount of rutile. The mean particle diameter from the Brunauer-Emmett-Teller surface area and transmission electron microscopy measurements ranged from 9.4 to 16.6 nm. The specific surface area (92.5-163.5 m(2) g(-1)) of the prepared TiO(2) powders was found to be dependent on the synthesis conditions. The content of hydroxyl groups on the surface of the prepared TiO(2) sample was higher than those on commercial TiO(2), resulting in increased photocatalytic oxidation. The photocatalytic activity of the TiO(2) samples prepared in a methylene blue solution was strongly dependent on the crystallinity and specific surface area, which were affected by the TTIP vapor concentration and residence time.     

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.     

TiO2纳米棒载Pd催化剂的制备及其对甲酸的电催化氧化

利用水热合成和无机溶胶法,分别制备了具有棒状(TiO2-R)和无规则结构(TiO2-I)的锐钛矿相TiO2,并以之为载体制备得到Pd/TiO2电催化剂.循环伏安测试显示,与无规则TiO2相比,具有棒状结构的TiO2载Pd催化剂对甲酸氧化的电催化性能提高了70%;计时电流测试显示,运行3000 s后,甲酸在棒状TiO2载Pd催化剂上的氧化电流是无规则TiO2载Pd催化剂的16倍.其原因可能与TiO2纳米棒拥有更好的电子传导性且表面拥有较多的活性含氧基团有关,从而能够有效提高催化剂对甲酸氧化的电催化活性和抗毒化性能.     

Synthesis of Mg-Doped TiO2 nanoparticles under different conditions and its photocatalytic activity

In this study, TiO(2)- and Mg-doped TiO(2) nanoparticles with different dopant contents were prepared by sol-gel method. The prepared photocatalysts were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and diffuse reflectance spectroscopy (DRS) techniques. The results of BET analysis indicated a pore diameter of 8 nm and surface area of 48.5 m(2) g(-1). XRD patterns of pure and doped TiO(2) nanoparticles at 450 °C revealed that all phases are anatase. The particle size obtained from TEM was less than 20 nm. The band gap energy of Mg-doped TiO(2) nanoparticles was lower than that of TiO(2) . The photocatalytic activity of the pure and doped nanoparticles has been compared in the removal of C.I. Acid Red 27 (AR27). The photocatalytic activity of Mg-doped (0.2 mol%) TiO(2) for the degradation of AR27 was higher than that of bare TiO(2) nanoparticles. Results of total organic carbon analysis and changes in the AR27 UV-Vis peaks indicated 99% mineralization and extinguishing of all peaks in UV and visible regions is possible with Mg-doped TiO(2) nanoparticles. Removal efficiency of AR27 was sensitive to the parameters such as catalyst dose, pollutant concentration and light intensity.     

Bi3.25La0.75Ti3O12纳米线的可见光催化性能

研究了用一步水热法制备的掺镧钛酸铋(Bi_3.25La_0.75Ti₃O₁₂, BLT)纳米线的光学和可见光催化性能, 并对其晶体结构和微观结构用X射线衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段进行了表征. 结果表明, 制备的纳米线为纯相的Bi_3.25La_0.75Ti₃O₁₂, 平均直径约为25 nm. 室温光致发光谱(PL)显示BLT纳米线在433和565 nm附近有较强的发射峰, 分别对应激子发射和表面缺陷发光. 紫外-可见漫反射光谱(UV-Vis DRS)表明BLT样品的带隙能约为2.07 eV. 利用可见光(λ>420 nm)照射下的甲基橙降解实验评价了BLT样品的光催化性能. 结果表明, BLT的光催化活性比商用TiO₂催化剂P25、掺氮TiO₂和纯相钛酸铋(Bi₄Ti₃O₁₂, BIT)高得多. BLT光催化剂具有更高催化活性的原因是La³⁺离子掺杂拓展了BIT对可见光的吸收范围, 同时抑制了BIT的光生电子-空穴的复合.     

Mobility enhanced photoactivity in sol-gel grown epitaxial anatase TiO2 films

Epitaxial anatase thin films were grown on single-crystal LaAlO3 substrates by a sol-gel process. The epitaxial relationship between TiO2 and LaAlO3 was found to be [100]TiO2||[100]LaAlO3 and (001)TiO2||(001)LaAlO3 based on X-ray diffraction and a high-resolution transmission electron microscopy. The epitaxial anatase films show significantly improved photocatalytic properties, compared with polycrystalline anatase film on fused silica substrate. The increase in the photocatalytic activity of epitaxial anatase films is explained by enhanced charge carrier mobility, which is traced to the decreased grain boundary density in the epitaxial anatase film.     

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.     

负载金的掺氮二氧化钛的制备及其可见光催化性能

以纳米管钛酸为前驱体,采用水热法先制备得到新型N掺杂二氧化钛,然后用沉积沉淀法在N掺杂二氧化钛表面负载微量贵金属Au,制备得到负载Au的掺N二氧化钛.利用TEM、XRD、XPS、ESR和DRS等手段研究了样品的形貌、晶体结构、元素化学态和光谱吸收性质.样品光催化活性通过可见光催化降解丙烯进行评价,结果表明,样品N-TiO₂和Au/N-TiO₂具有明显的可见光(λ≥420 nm)催化活性.ESR结果表明,掺氮过程中生成的束缚单电子的氧空位是样品具有可见光响应的原因.     

FTIR study on the formation of TiO2 nanostructures in supercritical CO2

TiO(2) nanospherical and fibered structures were obtained via a one-step sol-gel method in supercritical carbon dioxide (scCO(2)) involving polycondensation of the alkoxide monomers titanium isopropoxide (TIP) and titanium butoxide (TBO) with acetic acid (HAc). The resulting materials were characterized by means of electron microscopy (SEM and TEM), X-ray diffraction (XRD), thermal analysis (TGA), and attenuated total reflection Fourier transmission infrared (ATR-FTIR) analysis. Depending on the experimental conditions, TiO(2) anatase nanospheres with a diameter of 20 nm or TiO(2) anatase/rutile nanofibers with a diameter of 10-100 nm were obtained. Fiber formation was enhanced by a higher HAc/Ti ratio and the use of the titanium isopropoxide (TIP) monomer. The mechanism of the microstructure formation was studied using in situ FTIR analysis in scCO(2). The FTIR results indicated that the formation of nanofibers was favored by a titanium hexamer that leads to one-dimensional condensation, while nanospheres were favored by a hexamer that permits three-dimensional condensation.     

以纳米微晶纤维素为模板的酸催化水解法制备球形介孔TiO_2

以纳米微晶纤维素(NCC)为模板剂,采用酸催化水解法制备了球形介孔TiO2(SP-TiO2).并采用扫描电镜、透射电镜、X射线衍射、紫外-可见漫反射光谱和低温N2吸附-脱附等手段对其进行了表征.结果表明,所制SP-TiO2为直径100～200nm的规整球形颗粒,单个球形颗粒由粒径为10～20nm的TiO2小晶粒组成.其介孔孔径为8.2～13.5nm,且随焙烧温度的升高而增大.NCC长链结构之间羟基键合所形成的狭小空间构成的微反应器,可有效限制TiO2前驱体的生长和团聚,诱导其晶粒自组装成球形结构,并抑制由锐钛矿相向金红石相转变.600oC焙烧的SP-TiO2表现出最高的光催化活性,对苯酚降解率达89%.     

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．     

具有高光催化活性的黑色TiO2（B）/锐钛矿双晶TiO2-x纳米纤维

高效TiO2基光催化材料的开发一直是催化领域的研究热点,主要的策略是如何有效地分离光生载流子.制备多晶相的TiO2材料可引入异质/相结结构使电子与空穴朝不同方向移动,从而避免电子与空穴复合;另外,在TiO2中掺杂其他金属或非金属也可以有效地降低电子与空穴的复合率,掺杂的元素作为电子捕获阱俘获光生电子,以实现电子空穴的有效分离.近些年,作为一种全新的掺杂剂,氧空穴可以有效改善TiO2的光催化活性,所制TiO2具有可见光的全光谱吸收能力,因此该类TiO2呈现出黑色.通过上述方法均可以制备出高活性TiO2基光催化材料,如果能够将这些方法耦合一起,则可能制备出活性更高的光催化剂.因此,本文将异相结结构和空穴掺杂耦合起来,用多孔钛酸盐衍生物在H2中高温焙烧制得一种全新的黑色TiO2(B)/锐钛矿双晶TiO2–x纳米纤维.不同于其他TiO2基光催化材料,该样品仅由Ti和O元素组成,通过Ti和O元素的组合,形成了双晶结构和空穴掺杂两种特殊的结构,借助场发射(FESEM)、拉曼光谱(Raman)、氮气物理吸脱附、X射线光电子能谱(XPS)、热重(TG)、紫外可见漫反射光谱(UV-Vis)和荧光光谱(PL)等表征分析了样品的结构及其光催化性能间构效关系. FESEM结果显示,黑色TiO2(B)/锐钛矿双晶TiO2–x为长1–5mm、宽0.2mm的纤维结构, Raman结果表明,锐钛矿相在特征波段(140 cm–1左右)和TiO2(B)的特征波段(220–260 cm–1)均发生蓝移,说明该两相中均存在氧空穴;该样表面未检测到Ti3+,因此氧空穴可能分散在TiO2(B)和锐钛矿相的体相中.根据黑色TiO2(B)/锐钛矿双晶TiO2–x和白色TiO2(B)/锐钛矿双晶TiO2的失重差,估算出前者的O/Ti原子比为1.97.光催化降解甲基橙实验结果显示,黑色TiO2(B)/锐钛矿双晶TiO2–x的光催化活性是白色双晶TiO2的4.2倍,锐钛矿TiO2的10.5倍,且连续反应10次后未出现失活现象,显示出了良好的光催化稳定性.前期,我们已经证明了白色TiO2(B)/锐钛矿双晶TiO2由于具有TiO2(B)和锐钛矿的异相结结构,致使其电子空穴有效地分离,从而表现出优异的光催化活性;本文的PL结果显示,由于氧空穴的引入,异相结与氧空穴两者共同作用,进一步促进了黑色TiO2(B)/锐钛矿双晶TiO2–x电子与空穴的有效分离,因此黑色TiO2(B)/锐钛矿双晶TiO2–x表现出高的光催化活性.由于其特殊的结构,黑色TiO2(B)/锐钛矿双晶TiO2–x纳米纤维将在环境与能源领域表现出良好的应用前景.     

TiO2纳米管电极金属离子掺杂的表征

采用浸渍法对TiO₂纳米管电极进行Zn²⁺、Fe³⁺、Cu²⁺离子的掺杂改性,并进行了各种性能表征.扫描电镜(SEM)及X射线衍射光谱(XRD)结果表明,金属离子掺杂后的TiO₂纳米管电极依然保持了良好的表面形态及锐钛矿晶型,纳米管的直径为60-100 nm,其晶面主要为101面;可见紫外漫反射光谱(DRS)分析表明,进行掺杂的TiO₂纳米管电极的光学性质有不同程度的改变,Zn²⁺、Fe³⁺和Cu²⁺掺杂的TiO₂纳米管电极的禁带宽度分别为3.37 eV3、.14 eV、2.86 eV.这表明掺Cu²⁺的TiO₂纳米管电极的吸收边带发生了明显的红移.