不同晶相TiO2负载Cu2O催化甲醛乙炔化反应

分别以金红石相和锐钛矿相TiO₂为载体, 采用液相还原-沉积法制备了Cu₂O/TiO₂催化剂. 采用氮气物理吸附-脱附(N₂-physisorption)实验、 氢气程序升温还原(H₂-TPR)、 X射线衍射(XRD)、 X射线光电子能谱(XPS)、 CO红外光谱(CO-IR)及高分辨透射电子显微镜(HRTEM)等技术, 研究了不同晶相TiO₂载体对Cu₂O/TiO₂结构及其催化甲醛乙炔化反应性能的影响. 结果表明, 以金红石相TiO₂为载体的催化剂炔化活性明显高于以锐钛矿相TiO₂为载体的催化剂, 原因在于金红石相TiO₂主要暴露(110)晶面, 其与铜物种的配位环境及较高的空位密度形成了更多的Cu—O—Ti结构物种, 表现为Cu₂O与TiO₂之间强的相互作用. 这导致Cu₂O高效转变为乙炔亚铜活性物种, 并保持了较高的分散度与稳定性, 抑制了过度还原物种金属Cu的生成, 进而使催化剂表现出较高的催化性能.     

混合相二氧化钛石墨烯复合物的制备及光催化性能

采用水热法制备了一系列混合相二氧化钛-石墨烯(TrG)的复合物, 并考察了石墨烯的用量对降解污染物甲基蓝的影响. 采用X射线衍射(XRD), 傅里叶变换红外(FTIR)光谱, 高分辨透射电镜(HRTEM), 拉曼光谱,紫外-可见漫反射吸收光谱(UV-Vis DRS), X射线光电子能谱(XPS)和比表面积(BET)等测试手段对复合材料进行表征. 结果表明, 复合材料中TiO₂为棒状的混合相, 且均匀分散在石墨烯表面. 由于石墨烯良好的吸光性能,混合相中的异质结和复合物的良好光电子传递能力以及高比表面积, 复合材料具有较高的光催化活性. 所制备的TrG复合材料在紫外光下降解甲基蓝的催化活性均高于纯TiO₂, 且当氧化石墨烯负载量为0.8% (质量分数,w)时, 复合材料TrG具有较好的光催化效果.     

钛纳米管负载锰催化剂的低温选择性催化还原脱硝性能

采用水热法合成了钛纳米管（TiNT）,以400℃焙烧后得到的TiO₂纳米管为载体,采用浸渍法制备了MnO_x/TiNT催化剂,用于低温NH₃选择性催化还原脱NO反应（SCR）。BET、TEM、XRD及TG测试表明,经过400℃焙烧之后的钛纳米管主要成分为锐钛矿型TiO₂,所制备的催化剂活性组分分散性较好。在模拟烟气条件下,考察了锰负载量、空速、O₂含量、氨氮比及进口NO浓度对MnO_x/TiNT的SCR催化性能的影响。在150℃、\[NH₃\]/\[NO\]比为1.2、O₂浓度为3%、NO浓度为0.06%、空速GHSV为23613.8h^-1、Mn的负载量为5%~15%的条件下,NO的转化率达到95%以上。反应气氛中单独通入水会造成催化剂的活性下降;切断H₂O,催化剂的活性可以恢复至初始水平。温度越高,催化剂抗水性能越好,而且水存在情况下的抗硫性能优于其单独抗硫性能。再次切断H₂O和SO₂,催化剂的活性逐渐上升,但不能恢复到初始水平。     

顺序浸渍法制备V-W/x(Mn-Ce-Ti)/y(Cu-Ce-Ti)/堇青石urea-SCR催化剂及其性能研究(英文)

用溶胶凝胶法制备了Mn-Ce/TiO2(用M表示)和Cu-Ce/TiO2(用C表示)催化剂,将M相、C相和V2O5-WO3(用V表示)用顺序浸渍法依次负载到堇青石蜂窝陶瓷载体(CC)上。用尿素选择性催化还原NOx(SCR)的转化率作为衡量指标对一系列的整体催化剂性能进行评价。催化剂的物理化学性能用N2吸附、CO2-TPD、NH3-TPD、XRD、XPS和H2-TPR等进行表征。结果表明,当M相优先于C相负载到CC上时,在0.01%SO2和10%H2O存在的情况下,V/3C/3M/CC复合催化剂仍比C相或M相单独负载到堇青石上表现出较高的活性,并且微量的SO2有利于催化剂活性的提升。XRD分析结果表明,Cu-Ce负载到TiO2溶胶上有助于锐钛矿相的形成,Mn-Ce负载到TiO2上有助于金红石相的形成。比表面积只与M或C相的负载量有关而与负载顺序无关。M或C相能够增加催化剂表面不同强度的酸性位。H2-TPR研究结果表明,V和Cu或Mn之间的相互作用提高了V的还原能力,进而增加了耗氢量。由XPS分析可知,催化剂表面较高的V4+/V5+比值和大量化学吸附氧的存在有利于催化剂活性的提升。     

Synthesis of nano-TiO2 assisted by diethylene glycol for use in high efficiency dye-sensitized solar cells

The performance of dye-sensitized solar cells(DSSCs) consisting of anatase TiO_2 nanoparticles that were synthesized via a hydrothermal method was studied.The synthesized TiO_2 nanoparticles were characterized by X-ray diffraction(XRD),nitrogen sorption analysis,scanning electron microscopy(SEM),high resolution transmission electron microscopy(HRTEM),and UV-vis spectroscopy.Then the J-Vcurve,electrochemical impedance spectroscopy(EIS),and open-circuit voltage decay(OCVD) measurement were applied to evaluate the photovoltaic performance of DSSCs.Compared with the commercial TiO_2nanoparticles(P25),the synthesized-TiO_2 nanoparticles showed better performance.By adding diethylene glycol(DEG) before the hydrothermal process,the synthesized TiO_2 nanoparticles(hereafter referred to as TiO_2-DEG particles) shows narrower size distribution,larger specific surface area,higher crystallinity,and less surface defects than TiO_2(DEG free) particles.The analysis of photovoltaic properties of DSSCs based on TiO_2-DEG particles showed that the recombination of electron-hole pairs was decreased and the trapping of carries in grain boundaries restrained.It was believed that the photoelectrode fabricated with the as-prepared TiO_2 nanoparticles improved the loading amount of dye sensitizers(N719).and enhanced the photocurrent of the DSSCs.As a result,the TiO_2-DEG particle based cells achieved a photo-to-electricity conversion efficiency(η) of 7.90%,which is higher than 7.53%for the cell based on TiO2(DEG free) and 6.59%for the one fabricated with P25.     

异相晶核法液相合成金红石型TiO2纳米晶

分别以SnCl₂·2H₂O和SnCl₄·5H₂O为锡源,采用胶溶晶核法,经沉淀和胶溶过程,在液相中一步合成了金红石型TiO₂.详细考察了各种胶溶条件对产物结构的影响,并通过两种锡源实验结果的比较对异相晶核法中两种锡源的成晶机理进行了分析.所合成的金红石型TiO₂晶粒度为20～50nm,两种方法获得完全金红石型TiO₂所需引入SnO₂的最低物质的量的分数分别为10%和8%.     

热处理对TiO2纳米管结构相变的影响

TiO₂纳米管为无定形结构,焙烧后则由无定形转变为锐钛矿型,纳米管的管状结构被破坏,晶型转变是TiO₂纳米管的管状结构破坏的根本原因.经热处理,原来的TiO₂纳米管部分转变为长棒状的金红石型晶柱结构,而原料TiO₂在较大温度范围内焙烧均未出现长棒状晶柱结构;TiO₂由A→R的相变温差很大,TiO₂纳米管的A→R相变温度比原料约低350℃;合成的TiO₂纳米管的比表面积和孔体积很大.     

阴离子对TiO2晶形的影响及光催化性能研究

以SO₄^2-、F^-、Cl^-和PO₄^3-作为阴离子来研究其对水热合成TiO₂(分别记为TiO₂-S、TiO₂-F、TiO₂-Cl和TiO₂-P)晶体的影响,并考察了其光催化性能.SEM显示TiO₂-S、TiO₂-F、TiO₂-Cl和TiO₂-P分别呈粒子、十面体、刺球和不规则块状.XRD图谱表明TiO₂-S和TiO₂-F为锐钛矿晶型,TiO₂-Cl为金红石晶型,而TiO₂-P为锐钛矿、金红石和板钛矿混合晶型,这一结论也被紫外-可见漫反射实验所证实.XPS能谱表明这4种TiO₂纳米材料都受到了各自阴离子掺杂的影响,光催化试验显示:它们的光催化活性顺序为: TiO₂-F>TiO₂-S>TiO₂-Cl>TiO₂-P,这表明锐钛矿的光催化活性要大于金红石和板钛矿,且具有{001}面,掺杂了F的锐钛矿光催化活性更强.     

一维TiO2锐钛矿/金红石异相结的制备及光催化降解甲醛性能

TiO₂异相结主要通过高温方法制备,所制备材料的形貌和组成较难控制,尤其是在较低温度下一步制备一维TiO₂异相结仍具有一定的挑战性。采用简单、方便的一步水热法,在较低温度下(180℃)制备了一维纳米TiO₂异相结材料。X射线衍射(XRD)和高分辨透射电镜(HRTEM)分析表明,制备的材料以一维金红石相TiO₂纳米棒(长度:(400±50)nm,直径:(60±5)nm)为基本结构,粒径分布均匀的锐钛矿相TiO₂纳米粒子(直径:(9.5±0.5)nm)高密度、单分散地负载在纳米棒上。通过控制水热反应时间成功调控了异相结中锐钛矿相TiO₂的含量(20%~50%),进而实现了其光催化降解HCHO性能的调控。实验结果表明,当锐钛矿相TiO₂的含量为33%时(TiO₂-24,水热时间24 h制备的样品),异相结光催化剂表现出最佳的HCHO降解性能:在低光强LED灯(波长为365 nm,光强为12.26 mW·cm^-2)照射下,浓度约为120 mg·L^-1的HCHO气体在25 min后的降解率达到了92%,实现了高效、快速地去除空气中的HCHO(矿化为CO₂)。稳态荧光光谱和光电化学测试表明,与其他水热时间的样品相比,TiO₂-24具有更高效的光生电荷分离和传输效率。一维TiO₂异相结不仅有利于光生电荷的传输,而且对电荷的分离具有定向驱动作用,使其具有较高的光催化降解HCHO性能。     

物理混合法制备分级混晶TiO2微纳米材料及其光催化性能

通过物理混合法可控合成了分级混晶TiO₂微纳米材料, 采用扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线衍射仪(XRD)、 X射线光电子能谱仪(XPS)和固体紫外-可见分光光度计(UV-Vis)等对该微纳米材料进行了表征, 并评价了不同混晶比材料的光催化性能. 结果表明, 所得材料是由均匀负载金红石纳米颗粒的锐钛矿纳米片组装的三维分级结构. 其具有很高的光催化活性, 分级结构和混晶异相结的同时引入是提高材料光催化活性的关键.     

Synthesis of nanosized TiO2 particles in reverse micelle systems and their photocatalytic activity for degradation of toluene in gas phase

Nanosized pure TiO₂ particles with high crystallinity and large surface area were prepared by hydrolysis of tetrabutyl titanate in water/Triton X-100/isooctane reverse micelle solutions as reaction media followed by hydrothermal treatment to improve crystallinity. The prepared TiO₂ nanoparticles were characterized by XRD, BET, TGA, FT-IR and TEM. The size of ultrafine particles was controlled by changing the water content of the reverse micelle solution. The TiO₂ particles showed monodispersity, large surface area and high degrees of crystallinity and thermostability. The photocatalytic activity of the TiO₂ particles was evaluated by decomposition of toluene in the gas phase. The activity of the TiO₂ nanoparticles was higher than that of commercially available anatase fine particles, such as ST-01, which is one of the most active photocatalysts for degradation of organic compounds in the gas phase.     

用表面处理法降低TiO2粉末光活性问题的研究

本工作采用了两种简便的方法即用不同金属盐和金属氧化物对两种晶型(锐钛矿型和金虹石型)TiO₂粉末进行表面处理来降低TiO₂的光活性并对两种表面处理方法的优缺点作了比较,在评价TiO₂光活性时采用异丙醇光氧化反应的方法。实验证明,用金属盐表面处理TiO₂,其光活性有明显降低。用金属氧化物对TiO₂进行表面处理,在氧化物/TiO₂比例适当时也可以得到与金属盐表面处理TiO₂的同样效果。此外,我们还对TiO₂表面处理后能降低其光活性的作用机制问题进行了讨论。     

块状TiO2气凝胶的制备及其表征

随着以溶胶-凝胶法和超临界干燥技术为基础的气凝胶制备方法的逐步完善,已不断制备出多种气凝胶[1～3].由于TiO2具有半导体特性,它常被作为光催化剂而受到重视,但是TiO2气凝胶的结构强度远比SiO2气凝胶小,在制备过程中极易碎裂粉化,所以至今未见制备块状TiO2气凝胶的报道.Dagan等[4]曾用异钛酸丁酯为母体制得TiO2气凝胶,并发现水杨酸在TiO2气凝胶存在下的光解速率是一般TiO2粉末的10倍,但获得的仅为TiO2气凝胶粉末.张敬畅等[5]以无机盐为原料,采用溶胶-凝胶法结合超临界干燥技术制备了纳米级TiO2气凝胶,也未能得到块状TiO2气凝胶材料. 本文报道以正钛酸丁酯为原料制备块状TiO2气凝胶的方法,并用TEM,SEM,XRD和IR等手段对所获得的气凝胶进行了结构表征.     

方形锐钛矿TiO2纳米晶的合成及表征

在不添加任何模板剂或形状控制剂的条件下,以TiCl₄为前体,经氨水沉淀、乙醇洗涤和超临界干燥(AS制备法)选择性地合成了方形锐钛矿TiO₂纳米单晶.热稳定性研究结果表明,当焙烧温度不超过650℃时,方形锐钛矿TiO₂纳米晶的表面积、孔容、晶粒/颗粒尺寸基本保持不变.XRD和拉曼光谱分析表明,方形锐钛矿TiO₂纳米晶在800℃下焙烧后仍能保持晶相不变,表现出很强的抗晶相转变能力.但在1000℃焙烧后,样品可以完全转变成金红石相TiO₂.     

Properties of TiO2-polyacrylic acid dispersions with potential for molecular recognition

Titanium dioxide (TiO₂)/polyacrylic acid (PAA) (TiO₂/PAA) particles were formed by mixing PAA and an acidic solution of TiO₂ nanoparticles in dimethylformamide (DMF) followed by heat treatment. TEM and particle analysis showed that the resulting particles had a narrow size distribution. The colloid was very stable and aggregation was not observed over a wide pH range (3–9) or at high salt concentration. The residual carboxylic acid of PAA could be modified via EDC/NHS activation to form an amide bond with a protein. An antibody was attached to the hybrid nanoparticle and specific binding to antigen was monitored by surface plasmon resonance. The results suggest that TiO₂/PAA nanoparticles are candidates as the base component of a photocatalytic system with potential for substrate selectivity.     

Pt/TiO2纳米纤维的制备及其对甲醇的电催化氧化活性

采用静电纺丝技术结合还原浸渍法制备了Pt/TiO₂纳米纤维电催化剂, 通过X射线衍射(XRD)分析、扫描电镜(SEM)、透射电镜(TEM)和X射线能谱(EDS)等测试手段对样品的晶相、形貌、微结构和化学组成进行了表征. 测试结果表明, TiO₂纳米纤维为锐钛矿和金红石组成的混晶, Pt 纳米颗粒均匀地分布于TiO₂纳米纤维的表面, 且Pt 颗粒大小较均一, 平均粒径为4.0 nm, Pt/TiO₂纳米纤维中Pt 的质量分数约为20%. 采用三电极体系的循环伏安和计时电流电化学分析方法研究了样品在酸性溶液中对甲醇的电催化氧化活性, 结果表明, 与负载相同质量分数Pt 的Pt/P25 和商业Pt/C 催化剂相比较, Pt/TiO₂纳米纤维催化剂对甲醇呈现出较高的电催化氧化活性和更好的稳定性.     

Electrochemical and gas-phase photocatalytic performance of nanostructured TiO2(B) prepared by novel synthetic route

Nanostructured phase pure TiO₂(B) with microfibrous morphology was synthesized by newly developed protocol employing amorphous TiO₂ as a precursor. Compared to traditional syntheses from K₂Ti₄O₉, the new product exhibited better electrochemical performance and stability. Cyclic voltammetry of Li-insertion into the TiO₂(B) evidences a pseudocapacitive faradaic process of Li accommodation which is basically different from the diffusion-controlled lithium storage in anatase or rutile. The presence of two pairs of peaks in cyclic voltammogram with formal potentials of ca. 1.5 and 1.6 V is specific for TiO₂(B). This enables to use cyclic voltammetry for identification of this phase in a broad palette of TiO₂ materials of various origin.

The photocatalytic activity of TiO₂(B) in a gas phase was evaluated using the total oxidation of propane with oxygen and the photocatalytic reduction of NO to N₂ in an oxygen rich gas mixture. For the total oxidation of propane in the gas mixture containing 300 ppm propane and 20% oxygen, the reaction rates per 1 m²/g of the BET surface area of the catalyst for TiO₂(B) prepared by our protocol and Hombifine N (anatase, S_BET = 300 m²/g) are comparable. For the photocatalytic NO reduction to N₂ in an atmosphere containing 20% oxygen the ratio of quantum yields for TiO₂(B) and Hombifine N was found to be 0.08, which is roughly equivalent to the ratio of their BET surface areas (0.09), despite different phase composition of both materials. In comparison with the standard catalyst our material exhibited higher selectivity in the reduction of NO to N₂.     

Hierarchical TiO2 Flower-spheres with Large Surface Area and High Scattering Ability: an Excellent Candidate for High Efficiency Dye Sensitized Solar Cells

Hierarchical TiO₂ flower-spheres assembled from porous nanosheets-stacked of nanoparticles were synthesized by a simple hydrothermal method with one-step. The as-prepared TiO₂ flower-spheres showed a diameter range from 200 nm to 550 nm and a large surface area of 188 m²/g. A double layer photoanode made of P25 nanoparticles and as-prepared TiO₂ flower-spheres was fabricated for the dye sensitized solar cells(DSSCs). The efficient light scattering and dye absorption of the photoanode can be attributed to the top-layer of hierarchical TiO₂ flower-spheres. DSSCs based on the double layers photoanode exhibit a higher energy conversion efficiency of 8.11% with a short-circuit photocurrent density of 17.87 mA/cm², indicating that there is an increase of 38% in the conversion efficiency compared to those based on electrode P25(5.91%, 14.09 mA/cm²).     

LaCoO_3-TiO_2纳米管阵列的构筑及可见光光催化性能

TiO_2纳米管阵列具有较高的光催化活性,但可见光吸收弱,限制了其太阳能利用和环境应用。窄带隙的钙钛矿(ABO3)型氧化物能够吸收大范围波段的可见光,且稳定性高,但光催化活性低。本文首先采用溶胶-凝胶法合成了LaCoO_3纳米颗粒,然后利用电泳沉积技术将LaCoO_3纳米颗粒修饰于TiO_2纳米管阵列表面,构筑了LaCoO_3-TiO_2纳米管阵列。扫描电子显微镜(SEM)、透射电子显微镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)的表征结果显示溶胶-凝胶法合成的纳米颗粒为LaCoO_3,其尺寸均匀,结晶度高,平均粒径约为100nm。LaCoO_3纳米颗粒与TiO_2纳米管阵列之间的结合力好。紫外可见吸收光谱(DRS)显示,随着电泳沉积时间的延长,LaCoO_3-TiO_2纳米管阵列的吸收带边逐渐红移700nm。可见光下光催化降解甲基橙(MO)的结果表明,电泳沉积15 min制得的LaCoO_3-TiO_2纳米管阵列对MO的光催化效率最高,其降解速率是相同条件下TiO_2纳米管阵列的4倍。光致发光光谱和电化学阻抗谱证实LaCoO_3纳米颗粒的负载有效地促进了光生电荷的分离和传输,可见光光催化活性明显增强。     

Template Synthesis and Characterization of Cu2O/TiO2 Coaxial Nanocable for Photocatalysis

Coaxial nanocable consisted of p-type Cu₂O nanowires and n-type TiO₂ nanotubes arrays was prepared in the porous anodic aluminum oxide(AAO) template via the sol-gel method and subsequent electrodeposition method. X-ray diffraction analysis identified an anatase structure of the TiO₂ nanotubes and cubic structure of the Cu₂O nanowires. The obtained samples were also characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and energy dispersive X-ray spectroscopy(EDS). The diffrence of open circuit potential of the coaxial nanocable electrode was larger than that of the TiO₂ nanotubes electrode under ultraviolet illumination, which means doping with Cu₂O could improve the photovoltage effectively. Meanwhile, nanocable arrays exhibited a high activity for photodegrading Rhodamine B under Xe lamp irradiation and the photocatalysis degradation efficiency was up to 98.69% after degradation for 7 h. The enhanced photocatalytic activity could be attributed to the high migration efficiency of photoinduced electrons, which may suppress the charge recombination effectively.