N掺杂对TiO2形态结构及光催化活性的影响

以TiCl₄为钛源,采用酸催化水解法合成TiO₂前驱体,在NH₃/N₂气氛下经不同温度处理制得浅黄色的N掺杂TiO₂(TON)光催化剂。以苯酚为模型物,考察了催化剂在紫外光区、可见光区及太阳下催化活性;采用DRS、XPS、XRD、FTIR、SEM及低温氮物理吸附对光催化剂的晶相结构、光谱特征和表面结构等进行表征。系统研究了N掺杂对TiO₂形态结构及光催化活性的影响。结果表明,掺杂N以阴离子形式进入TiO₂体相中置换晶格中的O,适宜温度下制得适量N掺杂的TON在紫外光区、可见光区及太阳光下均表现出较高的活性。N掺杂在TiO₂表面生成Ti-O-N键,形成新的能级结构,使催化剂的吸收红移至450～550 nm,诱发TiO₂可见光催化活性。同时高温下煅烧,N掺杂可抑制TiO₂晶粒生长,减缓TiO₂粒子间团聚,提高锐钛矿相向金红石相转变温度,减缓相转化速度。     

掺氮TiO2可见光降解有机污染物的比较研究

用溶胶-凝胶法制备了不同掺杂量的N/TiO₂复合纳米粉末, 采用X射线衍射(XRD)、扫描透镜(TEM)、紫外-可见反射吸收光谱(UV-vis)对催化剂进行了初步表征. 通过X射线光电子能谱(XPS)、元素分析仪(EA)测定其含氮量. XPS分析结果显示TiO₂晶格中的氧被氮原子取代, N/TiO₂表面存在Ti^3＋离子; 紫外-可见反射吸收光谱测得不同掺杂量的N/TiO₂的禁带宽度(E_g), 推测在TiO₂价带上方生成了由N诱导产生的中间带, 当氮、钛摩尔比为0.0880时N/TiO₂的E_g最小, 为2.50 eV. 在可见光下, 以酸性桃红(SRB)和无色小分子对氯苯酚(4-CP)作为可见光活性实验的探针反应, 确定了最佳掺杂比为n_N/n_Ti＝0.0880. 结果表明, 最佳掺杂量下N/TiO₂能显著降解SRB和4-CP, 通过测定ESR, IR, TOC, COD, 重点比较了TiO₂在掺杂N前后在降解SRB和4-CP时的差异, 包括氧化物种、矿化率、最终产物等, 证明在可见光下, N/TiO₂的降解机理为电子从独立的N 2p轨道激发到Ti 3d轨道, 产生羟基自由基等氧化物种, 达到降解有机物的目的.     

掺氮TiO2可见光降解有机污染物的比较研究

用溶胶-凝胶法制备了不同掺杂量的N/TiO₂复合纳米粉末, 采用X射线衍射(XRD)、扫描透镜(TEM)、紫外-可见反射吸收光谱(UV-vis)对催化剂进行了初步表征. 通过X射线光电子能谱(XPS)、元素分析仪(EA)测定其含氮量. XPS分析结果显示TiO₂晶格中的氧被氮原子取代, N/TiO₂表面存在Ti^3＋离子; 紫外-可见反射吸收光谱测得不同掺杂量的N/TiO₂的禁带宽度(E_g), 推测在TiO₂价带上方生成了由N诱导产生的中间带, 当氮、钛摩尔比为0.0880时N/TiO₂的E_g最小, 为2.50 eV. 在可见光下, 以酸性桃红(SRB)和无色小分子对氯苯酚(4-CP)作为可见光活性实验的探针反应, 确定了最佳掺杂比为n_N/n_Ti＝0.0880. 结果表明, 最佳掺杂量下N/TiO₂能显著降解SRB和4-CP, 通过测定ESR, IR, TOC, COD, 重点比较了TiO₂在掺杂N前后在降解SRB和4-CP时的差异, 包括氧化物种、矿化率、最终产物等, 证明在可见光下, N/TiO₂的降解机理为电子从独立的N 2p轨道激发到Ti 3d轨道, 产生羟基自由基等氧化物种, 达到降解有机物的目的.     

B离子掺杂TiO2催化剂(TiO2－xBx)光催化活性的研究

采用溶胶-凝胶法制备出纳米TiO₂和TiO_2－xB_x催化剂. 光催化实验证明, TiO_2－xB_x催化剂的紫外、可见光催化活性均高于TiO₂. XRD, XPS和Raman结果表明, B离子是以取代式掺杂占据了TiO₂的O^2－的晶格位置. UV-Vis和PL谱的结果表明, B离子的2p轨道与O的2p轨道形成混合价带, 产生可见光响应, B离子的掺入有效地阻止了光生载流子的复合, 促进了其分离, 是TiO_2－xB_x催化剂紫外、可见光催化活性提高的主要原因.     

TiO2光子晶体的光子带隙及其应用

最近利用TiO₂光子晶体控制光子的研究取得了一定进展。本文概述了TiO₂光子晶体的分类、性质、制备和应用。TiO₂光子晶体在反射器件、光电转换、化学传感器和光催化等方面应用前景广阔,目前,可见光和近红外波段的TiO₂光子晶体的合成是工作的难点,本文对今后TiO₂光子晶体的研究提出了展望。     

N, S共掺杂纳米TiO2：水解-溶剂热法合成及可见光催化活性

采用简单的两相分离的水解-溶剂热法,以硫脲为非金属原料,可控地制备了N,S共掺杂的纳米TiO₂。所获得的纳米TiO₂平均粒径为10nm、粒径分布集中,且分散性好。N,S共掺杂拓展了纳米TiO₂对可见光的响应范围。气氛可控的表面光电压谱（SPS）的测试结果表明,N,S共掺杂引起的表面态能够捕获光生空穴,进而有利于光生电荷分离。在可见光催化氧化水产氧及降解污染物乙醛的过程中,共掺杂的纳米TiO₂表现出了高的活性,甚至优越于N掺杂的。这主要归因于N,S共掺杂的纳米TiO₂分散性好、可见光吸收强和光生电荷分离高。     

掺杂Fe2O3对吸附相反应技术制备TiO2的形貌和光催化性能的影响

利用吸附相反应技术制备得到了掺杂不同浓度的Fe₂O₃的TiO₂复合光催化剂。通过透射电子显微镜(TEM)、紫外可见光谱和X射线衍射(XRD)研究不同掺杂浓度对TiO₂形貌和结晶过程的影响,并利用3种波长光源下的甲基橙光降解实验考评了各个复合光催化剂的催化活性。结果表明,掺杂后复合光催化剂中Fe₂O₃分散性较好较均匀。在TiO₂紫外可见吸收光谱中由于Fe₂O₃的掺杂而出现了红移,而且随着掺杂浓度增加红移越来越明显,复合光催化剂的禁带宽度也越来越小。在焙烧过程中无定形Fe₂O₃或Fe³⁺进入了TiO₂的晶格结构,从而抑制了TiO₂的结晶过程。半导体禁带宽度的减少以及TiO₂结晶过程的抑制作用,都导致紫外光下复合光催化剂催化活性的降低。但Fe₂O₃的掺杂也使得复合光催化剂在可见光区出现了一定的光催化活性。     

B离子掺杂TiO2催化剂(TiO2－xBx)光催化活性的研究

采用溶胶-凝胶法制备出纳米TiO₂和TiO_2－xB_x催化剂. 光催化实验证明, TiO_2－xB_x催化剂的紫外、可见光催化活性均高于TiO₂. XRD, XPS和Raman结果表明, B离子是以取代式掺杂占据了TiO₂的O^2－的晶格位置. UV-Vis和PL谱的结果表明, B离子的2p轨道与O的2p轨道形成混合价带, 产生可见光响应, B离子的掺入有效地阻止了光生载流子的复合, 促进了其分离, 是TiO_2－xB_x催化剂紫外、可见光催化活性提高的主要原因.     

Au改性TiO2纳米复合物对人结肠癌细胞的光催化杀伤作用

提出了通过TiO₂表面修饰纳米Au的方法来提高纳米TiO₂光催化杀伤癌细胞的效率. 采用化学还原法合成了Au改性的TiO₂ (Au/TiO₂)纳米复合物, 并研究了不同掺杂量(1 wt%, 2 wt%, 4 wt%)的Au/TiO₂对人结肠癌LoVo细胞的光催化杀伤效应. 结果显示, Au的掺杂大大地提高了TiO₂纳米粒子光催化杀伤结肠癌LoVo细胞的效率, 而且Au掺杂量的高低影响Au/TiO₂光催化杀伤癌细胞的效率, 掺金量为2%的Au/TiO₂对结肠癌LoVo细胞具有最高的光催化杀伤效率. 在光强为1.8 mW/cm²的紫外灯(λ_max＝365 nm)下光照110 min, 50 μg/mL掺金量为2%的Au/TiO₂能够杀死所有的癌细胞, 而同样浓度的TiO₂只能杀死70%的癌细胞.     

金属离子掺杂对TiO2光催化性能的影响

TiO₂光催化反应过程涉及光生电荷、电荷迁移、电荷在TiO₂表面的反应和溶液体相反应4个顺序相接并相互影响的步骤.在TiO₂中掺杂金属离子对以上4个步骤均有重要影响,合理的掺杂可有效地提高其光催化性能.本文综合了国内外此方面的最新研究成果,从提高TiO₂光催化性能和优化光催化反应的角度出发,在材料吸光能力、电荷扩散、表面反应、粒径和晶型等方面,全面地分析总结了金属离子掺杂的影响效果和规律性认识,并对TiO₂基光催化材料的金属离子掺杂改性研究的未来发展方向提出了建议.文中还简要介绍了相关的掺杂方法和材料表征手段.     

非金属掺杂改性TiO_2光催化剂的机理

为了扩展TiO2光催化剂对可见光的利用,以非金属元素对其进行掺杂和改性是近年来很活跃的研究内容,文献报道主要有氮、碳、硫、氟等非金属元素的改性结果。各种不同的改性方法如高温气氛还原、脉冲激光沉积、离子溅射、机械化学、溶液湿法等都可以得到非金属元素改性。本文重点探讨了氮改性TiO2光催化剂的结果,氮改性TiO2的方法和改性机理,讨论了氮改性TiO2的结构及其对可见光的利用机理等,对碳、硫、氟等元素掺杂改性也作了简要介绍。     

Strategies developed on the modification of titania for visible light response with enhanced interfacial charge transfer process: an overview

The modification of titania by metal / non metal ion doping, coupling with narrow band gap sensitizer, surface flourination, metal deposition, and together with recent ventures on application of {001} facets of anatase titania for visible light response with enhanced charge carrier separation are briefly overviewed.     

Photocatalytic mechanisms of modified titania under visible light

Heterogeneous photocatalysis with titania under visible light has increasingly been a focus for research. Metal or non-metal doping, surface sensitization, semiconductor coupling, precious metal deposition and increasing crystal defects have been used to enhance the photocatalytic activity of titania under visible light. Based on the research results of different modification methods in recent years, some mechanisms from the excitation, bulk diffusion and surface transfer of photoinduced charge carriers, such as band gap modification, changing the excitation path, promoting the separation of photogenerated charge carrier, improving the surface adsorption and reaction, and synergistic effects, for photocatalysis under visible light are discussed and the development trend in this field is predicted.     

Titania supported gold nanoparticles as photocatalyst

This Perspective is focused on the photocatalytic activity of gold nanoparticles supported on titania (Au/TiO(2)). Titania is the most widely used photocatalyst, but its limited activity under visible light irradiation has motivated the quest for modified titania materials absorbing visible light. The review starts by justifying how doping with metallic elements is a related strategy, but different, to that leading to the use of Au/TiO(2) in photocatalysis. Data supporting and confirming the photoactivity of gold nanoparticles in colloidal solutions are briefly presented to justify the possibility of gold photosensitization of titania by electron injection into the conduction band. After describing the most common procedures used to prepare Au/TiO(2), the central part of this article is focused on the photocatalytic activity reported for Au/TiO(2) for hydrogen generation, dye decoloration, phenol decomposition and carboxylic acid degradation, among other processes. Emphasis is given to the role that parameters like Au loading, particle size, surface area, spatial structuring and others play on the photocatalytic activity. One important issue has been to distinguish those reports using visible light from those other in which direct titania excitation by UV light has been used. These Au/TiO(2) photocatalysts can find real applications in the near future for environmental remediation and for hydrogen generation.     

Theoretic and Experimental Studies on Titania Nanotube Doped with Ag Metal Ions

The electronic state density and energy bands of Ag-doped anatase TiO2 are studied by WIEN2k software package based on DFT. The calculation results show that the band-gap of anatase titania became bigger after doping with Ag metal ions. The band-gap transfers from 2.04 to 2.5 eV, but a new energy band appears among the forbidden band after the Ag atom substitution. The interband width of Ag-TiO2 is 0.17 eV, which is located at –0.07 eV; more excitation and jump routes are opened for the electrons. The lowest excitation energy can achieve 1.2 eV, which may allow the photons with lower energy (at longer wavelength, such as visible light) to be absorbed. Ag ions are implanted into the titania nanotube sample by MEVVA (Metal Vapor Vacuum Arc) implanter. The photo-electrochemical response and photo-degradation experiment of titania nanotube samples implanted with Ag ions are tested under UV and visible light; the results indicated that the performance of implanted titania naotubes is enhanced both under UV and visible light; it is worth mentioning that the photocurrent density can reach 0.145 mA/cm2 under visible light, which is 181 times higher than those of pure TiNT, and the k value of degradation methyl orange can obtain 0.30 h-1, which is 71 times higher than that of pure TiNT. All the experimental results are consistent well with the theoretic ones.     

硫和银共掺杂介孔TiO2的制备表征及光催化活性

以P123为模板,以钛酸四正丁酯、硝酸银和硫脲为原料采用模板法制备了一系列硫和银共掺杂介孔TiO2光催化材料。利用扫描电子显微镜（SEM）、X射线衍射（XRD）、BET和紫外-可见光谱（UV-Vis）等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征。以甲基橙溶液的光催化降解为模型反应, 考察了不同掺杂量的样品在紫外和可见光下的光催化性能。结果表明：用模板法制备的共掺杂介孔TiO2光催化材料在紫外和可见光条件下较纯介孔TiO2和单掺杂介孔TiO2对甲基橙溶液具有更好的光催化降解效果, 且硫和银的掺杂量及样品焙烧温度显著影响该材料的催化性能。当硫掺杂量为2%（mol）和银掺杂量为1%（mol）,在500℃焙烧2 h所得光催化材料的催化性能最佳, 4 h即可使甲基橙的降解率达98.8%,重复使用4次仍可使甲基橙的降解率保持在87.5%以上。因此, 以该模板合成法, 通过硫和银的共掺杂有望使TiO2成为一种低或无能耗、高活性的绿色环保型催化材料。     

Thermal properties of undoped, S-doped, Nb-doped, and S, Nb co-doped titania nanoparticles prepared by sol–gel method

One of the classic methods to extend the spectral response of a wide band gap titania semiconductor to visible light is impurity doping. This study has studied undoped, S-doped, Nb-doped, and S, Nb co-doped titania nanopowders prepared by sol–gel. The relationship between the doping conditions and the thermal stability, phase composition, crystallinity, morphology of particles, and the influence of dopant in similar conditions was investigated. Also the relationship between the dopant and the properties of titania nanosized powders, such as thermal stability, phase composition, crystallinity, morphology and size of particles, was investigated. Thermogravimetry coupled with differential thermogravimetry, X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscope was used for the characterization of the materials. During heating of the air dried samples, their chemical degradation took place giving rise to anatase phase.     

Effects of calcining temperature on photocatalytic activity of Fe-doped sulfated titania

Using industrial titanyl sulfate as a raw material, Fe‐doped sulfated titania (FST) photocatalysts were prepared by using the one‐step thermal hydrolysis method and characterized using XRD, SEM, TGA–DSC, FTIR, UV–Vis DRS and N₂ adsorption–desorption techniques. The effects of calcining temperature on the structure of the titania were investigated. The photocatalytic activity of the FST was evaluated using the photodegradation of methylene blue and photooxidation of phenol in aqueous solutions under UV and visible light irradiation, respectively. The results evinced that Ti⁴⁺ is substituted by Fe³⁺ in titania lattice and forms impurity level within the band gap of titania, which consequently induces the visible light absorption and visible‐light‐driven photocatalytic activity. The synergistic effects of Fe‐doping and sulfation are beneficial to the efficient separation of the photogenerated carriers and also improve the quantum efficiency of photocatalysis. In addition, Brönsted acidity arisen from the strong inductive effect of sulfate is also conducive to enhancing the photocatalytic performance of FST. However, when the calcining temperature is higher than 800°C, sulfur species and surface hydroxyl groups decompose and desorb from FST and the specific surface area decreases sharply. Moreover, severe sintering and rutile phase formation occur simultaneously. All these are detrimental to photocatalytic activity of FST.     

Generation of low-molecular-weight organic compounds in water by titania photocatalyst under UV-Vis light radiation

We attempted to develop a new type titania photocatalyst that, when activated, responded in not only the ultraviolet rays region but also visible light radiation region by the new titania photocatalyst with the zirconia and nitrogen simultaneously introduced in the titania lattice. The decomposition performance of the standard organic compound in water by this new type titania photocatalyst nanoparticle was compared with the conventional type under both the ultraviolet ray and visible light radiation conditions. It was suggested that the low-molecular-weight organic compounds were also generated from the organic compound in water by the new type titania photocatalyst activities under the visible light radiation.     

Bismuth-doped ordered mesoporous TiO2: visible-light catalyst for simultaneous degradation of phenol and chromium

A controllable and reproducible synthesis of highly ordered two-dimensional hexagonal mesoporous, crystalline bismuth-doped TiO(2) nanocomposites with variable Bi ratios is reported here. Analyses by transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy reveal that the well-ordered mesostructure is doped with Bi, which exists as Bi(3+) and Bi((3+x+)). The Bi-doped mesoporous TiO(2) (ms-TiO(2)) samples exhibit improved photocatalytic activities for simultaneous phenol oxidation and chromium reduction in aqueous suspension under visible and UV light over the pure ms-TiO(2), P-25, and conventional Bi-doped titania. The high catalytic activity is due to both the unique structural characteristics and the Bi doping. This new material extends the spectral response from UV to the visible region, and reduces electron-hole recombination, which renders the 2.0% Bi-doped ms-TiO(2) photocatalyst highly responsive to visible light.