原位碳、氮共掺杂二氧化钛空心球的制备与可见光光催化性能

在H₂O₂-HF 的乙醇-水混合溶液中, 通过水热处理碳氮化钛(TiCN)制备了碳、氮共掺杂TiO₂ 空心球(CNTH). 用X 射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X 射线光电子能谱(XPS)和紫外-可见(UV-Vis)吸收光谱表征了所制备的样品. 在可见光(λ≥400 nm)照射下, 通过降解甲基蓝检测了碳、氮共掺杂TiO₂空心球的光催化活性. 结果表明, 源于TiCN中的部分碳和氮原子原位掺入了TiO₂的晶格中, 部分碳掺入TiO₂点阵的间隙中. 该材料在整个可见光区展示了增强的可见光吸收, 其带边明显红移. 光催化研究表明在强可见光吸收和独特的空心球结构的协同作用下, 碳、氮共掺杂TiO₂空心球展示了比P25更高的可见光光催化活性.     

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。     

氟掺杂TiO2纳米管的可见光催化活性及第一性原理计算

作为光催化技术的核心, 提高TiO₂的光催化活性和对可见光的利用率是当前光催化研究中最重要的研究课题. 为了提高TiO₂纳米管的可见光催化活性, 采用化学气相沉积法对TiO₂纳米管进行了氟掺杂. 扫描电子显微镜(SEM)结果表明退火温度对于TiO₂纳米管的形貌完整性有较大影响, 当样品在550和700 °C下退火, 氟掺杂TiO₂纳米管结构受损; X射线衍射(XRD)分析表明氟掺杂对TiO₂由锐钛矿相转化为金红石相有阻碍作用; X射线光电子能谱(XPS)测试表明化学气相沉积能有效地对TiO₂纳米管进行非金属掺杂, 且该方法安全、操作简单. 氟掺杂TiO₂纳米管对甲基橙有较高的可见光催化降解活性. 第一性原理计算结果表明氟掺杂对TiO₂带隙无显著影响, 费米能级附近的F 2p轨道电子位于价带底部, 与O 2p交联作用较小, 因此对TiO₂光吸收带边影响不大. 氟掺杂能促进表面氧空穴的产生, 增加表面酸度与Ti³⁺, 有利于减少电子-空穴复合率, 从而提高其光催化活性.     

超声波制备介孔结构的氮掺杂TiO2纳米晶及其可见光催化性能

采用超声波辐射法制备了具有介孔结构的高浓度氮掺杂TiO₂纳米晶(N/TiO₂).采用N₂物理吸附、X射线粉末衍射、X射线光电子能谱、透射电镜、光致发光谱和紫外-可见漫反射光谱等手段对N/TiO₂进行了表征.以波长为400~660nm的可见光为光源,以水体污染物邻苯二甲酸二甲酯为降解对象,考察了不同制备方法对N/TiO₂光催化性能的影响.结果表明,超声波辐射使氮掺杂浓度提高了2.2倍,该法制备的N/TiO₂同时具有较好的介孔结构,表现了更高的光催化降解邻苯二甲酸二甲酯的活性.其活性提高的主要原因是N/TiO₂含有更高浓度的氮和对可见光具有更强的吸收能力.     

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.     

用分子轨道理论研究NO气体在TiO2表面吸附

根据一氧化氮(NO)气体在二氧化钛(TiO₂)表面吸附和脱附的实验结果, 揭示了气体脱附量的变化规律. 利用MOPAC 和GAUSSIAN分子轨道理论计算了在TiO₂(110)表面上吸附NO分子的原子簇模型, 电荷分布以及原子簇的能级, 推断了NO在TiO₂(110)表面吸附的稳定性.     

Ag掺杂型空心TiO2纳米微球的制备与表征及其光催化性能

通过甲基丙烯酸与苯乙烯的乳液聚合制备了表面载有阴离子的聚苯乙烯(PSt)纳米乳胶粒. 在乙醇与水的混合溶剂中, 用硅烷偶联剂乙烯基三甲氧基硅烷对其进行表面改性. 以此乳胶粒为模板, 加入钛酸四丁酯和硝酸银制备了Ag₂O掺杂型聚苯乙烯/二氧化钛(PSt/TiO₂)复合微球. 对该微球在180 °C进行液相预处理、干燥、500 °C煅烧等步骤制备了Ag 掺杂型Ag-TiO₂复合粒子. 通过扫描电镜(SEM)、透射电镜(TEM)和X射线衍射(XRD)等手段对PSt/TiO₂复合粒子及Ag-TiO₂空心粒子的形貌及晶体结构等进行了表征. 考察了Ag-TiO₂复合粒子在紫外光(365 nm)与紫外-可见光(370-760 nm)下对罗丹明B (RhB)降解的催化活性. 结果表明, 与不含银的TiO₂空心微球相比, 在紫外光照射下, 银含量(n_Ag/n_Ti)为0.1%的Ag-TiO₂复合粒子对RhB的降解率提高了11%左右; 在紫外-可见光照射下, n_Ag/n_Ti为1.0%和2.0% 的Ag-TiO₂复合粒子对RhB的降解率提高了30%左右.     

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.     

Zr离子掺杂TiO2可见光催化剂光催化活性的研究

本文采用溶胶-凝胶法制备了Zr离子掺杂TiO₂光催化剂。光催化降解对氯苯酚实验表明,Zr离子掺杂浓度为10%时活性最高,其紫外光、可见光催化活性分别是纯TiO₂的1.5倍和4倍。利用XRD、Raman、XPS、UV-Vis DRS、PL等技术对样品进行了表征,结果表明：Zr离子以取代式掺杂方式进入TiO₂晶格,在TiO₂导带下方形成掺杂能级,增强了可见光响应,促进了光生载流子的分离,此外Zr离子掺杂在催化剂表面引入大量表面缺陷,增加了表面羟基物种,从而使得Zr离子掺杂TiO₂光催化剂的紫外、可见光催化活性显著提高。     

表面In掺杂TiO2的N719/TiO2-Inx%/FTO薄膜电极的光电转换效率

采用溶胶-凝胶法制备出In 表面修饰的TiO₂ (TiO₂-Inx%)纳米粒子, x%代表在In 掺杂的TiO₂样品中In³⁺与In³⁺和Ti⁴⁺离子摩尔百分含量. 利用二(四丁基铵)顺式-双(异硫氰基)双(2,2''-联吡啶-4,4''-二羧酸)钌(II)(N719)作为敏化剂, 制备出N719/TiO₂/FTO (氟掺杂锡氧化物)和N719/TiO₂-Inx%/FTO染料敏化薄膜电极. 光电转换效率实验表明, 在薄膜电极+0.5 mol·L^-1 LiI+0.05 mol·L^-1 I₂的三甲氧基丙腈(MPN)溶液+Pt 光电池体系中,N719/TiO₂-Inx%/FTO薄膜电极的光电转换效率均高于N719/TiO₂/FTO, 其中N719/TiO₂-In0.1%/FTO的光电转换效率比N719/TiO₂/FTO提高了20%. 利用X 射线衍射(XRD)、X 射线光电子能谱(XPS)、漫反射吸收光谱(DRS)、荧光(PL)光谱和表面光电流作用谱确定了TiO₂-Inx%样品中In3+离子的存在方式和能带结构; 利用表面光电流作用谱研究了N719/TiO₂-Inx%/FTO薄膜电极的光致界面电荷转移过程. 结果表明, In3+离子在TiO₂表面形成O-In-Cl_n (n=1, 2)物种, 该物种的表面态能级位于导带下0.3 eV处; 在光电流产生过程中, O-In-Cl_n (n=1, 2)表面态能级有效地抑制了光生载流子在TiO₂-Inx%层的复合, 促进了阳极光电流的增加, 从而导致N719/TiO₂-Inx%/FTO薄膜电极的光电转化效率高于N719/TiO₂/FTO, 并进一步讨论了光致界面电荷转移的机理.     

Cooperation among N,F and Fe in tri-doped TiO<Subscript>2</Subscript> photocatalyst

TiO₂ photocatalysts tri-doped with N, F and Fe were synthesized by a sol–gel method. The cooperation of N, F and Fe in tri-doped TiO₂ was verified by monitoring NH₃ decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption spectroscopy, and by the simulation based on the density functional theory (DFT). The results from NH₃ decomposition revealed that the cooperation of N, F and Fe broadened the optical response of TiO₂ to the visible light range and also enhanced the photocatalytic activity of TiO₂ under UV light. The reusability of the tri-doped TiO₂ sample after three cycles under UV and visible light irradiation was very good. XRD patterns and SEM and HRTEM images indicated that the tri-doped sample was nanometric anatase with a small amount of rutile with an average particle size of 18 nm. Tri-doping with N, F and Fe suppressed the phase transition from anatase to rutile and also resulted in some more lattice defects. XPS analysis showed that the N, F and Fe atoms were doped into the TiO₂ lattice. UV–Vis absorption spectra of the tri-doped TiO₂ showed that its optical absorption edge was moved up to 640 nm and its UV absorption was also enhanced. The DFT results confirmed that the cooperation of Fe 3d and N 2p orbits narrowed the band gap of TiO₂ and the F 2p orbit broadened the upper valence bands. The synergistic electron density around N, F and Fe in tri-doped TiO₂ was capable of enhancing the photochemical stability and reusability of TiO₂.     

Preparation, characterization and photocatalytic activity of visible light driven chlorine-doped TiO2

A novel chlorine-doped titanium dioxide catalyst with visible light response was prepared by hydrolysis of tetrabutyl titanate in hydrochloric acid. The catalyst samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Results showed that the doped element of Cl lowered the temperatures of phase transformation of TiO₂ from amorphous to anatase and from anatase to rutile. The absorption edge of chlorine-doped TiO₂ calcined at 300°C shifted to visible light region. X-ray photoelectron spectroscopy results proved that chlorine existed in the TiO₂ crystal lattice as anion. The photocatalytic degradation of phenol showed that under visible light (λ > 400 nm) irradiation, the chlorine-doped TiO₂ calcined at 300°C displayed the best performance, the degradation ratio of phenol was 42.5% after 120 min. Translated from Chinese Journal of Catalysis, 2006, 27(10): 890–894 [译自: 催化学报]     

Hierarchical chlorine-doped rutile TiO2 spherical clusters of nanorods: Large-scale synthesis and high photocatalytic activity

In this study, we report the synthesis of hierarchical chlorine-doped rutile TiO₂ spherical clusters of nanorods photocatalyst on a large scale via a soft interface approach. This catalyst showed much higher photocatalytic activity than the famous commercial titania (Degussa P25) under visible light (λ>420 nm). The resulting sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy, ¹H solid magic-angle spinning nuclear magnetic resonance (MAS-NMR) and photoluminescence spectroscopy. On the basis of characterization results, we found that the doping of chlorine resulted in red shift of absorption and higher surface acidity as well as crystal defects in the photocatalyst, which were the reasons for high photocatalytic activity of chlorine-doped TiO₂ under visible light (λ>420 nm). These hierarchical chlorine-doped rutile TiO₂ spherical clusters of nanorods are very attractive in the fields of environmental pollutants removal and solar cell because of their easy separation and high activity.     

Sized dependence and microstructural defects on highly photocatalytic activity based on multisized CdTe quantum dots sensitized TiO2

A series of sensitized TiO₂ NPs with enhanced photocatalytic activity were prepared by different sized CdTe QDs with bifunctional ligand interlinking. The microstructures and morphologies of four different sizes of CdTe QDs and CdTe QDs sensitized TiO₂ NPs were characterized systematically by fluorescence spectroscopy, UV-Vis diffuse reflectance spectroscopy, FT-IR, XRD, XPS, FE-SEM, HRTEM, BET, and positron annihilation lifetime spectroscopy (PALS). The photocatalytic performance of CdTe QDs sensitized TiO₂ NPs was investigated by degrading MO and MB in aqueous solution under visible light irradiation. The process of degradation complied with the first-order reaction kinetics. Four different sized CdTe QDs sensitized TiO₂ exhibited higher photocatalytic activities than TiO₂. Particularly, yellow emitting CdTe QDs (3.28 nm) sensitized TiO₂ (CT_1.5) showed the best photocatalytic performance, which may be attributed to the optimal NP size, and has a moderate light absorption and electron injection. The effect of microstructural defects on CdTe QDs sensitized TiO₂ has been confirmed effectively by positron lifetime measurements.     

Improved efficiency of dye-sensitized solar cells by design of a proper double layer photoanode electrodes composed of Cr-doped TiO2 transparent and light scattering layers

A new strategy for enhancing the efficiency of TiO₂ dye-sensitized solar cells (DSSCs) by design of a new double layer film doped with Cr ions, with various morphologies, is reported. X-ray diffraction and field emission scanning electron microscope (FE-SEM) analyses revealed that the synthesized nanoparticles had uniform and nanometer grains with different phase compositions and average crystallite size in the range of 10–12 nm depending upon Cr atomic percentage. UV–vis absorption showed that Cr introduction enhanced the visible light absorption of TiO₂ nanoparticles by shifting the absorption onset to visible light region. Furthermore, the band gap energy of nanoparticles decreased with an increase in dopant concentration due to reduction of particle size. It was found that, 3 at.% Cr-doped TiO₂ DSSC in the form of a double-layer film composed of TiO₂ nanoparticles, as the under-layer, and mixtures of nano- and micro-particles with weight ratio of 80:20, as the over-layer, (i.e., CT3/NM3 solar cell) had the highest power conversion efficiency of 7.02 %, short current density of 17.32 mA/cm² and open circuit voltage of 674 mV. This can be related to achievement of a balance among the electron injection, light scattering effect and dye sensitization parameters. Optimization of light scattering effect of photoanode electrode led to improve the photovoltaic performance of CT3/NM3 double-layer solar cell and was demonstrated by diffuse reflectance spectroscopy. The presented strategy would open up new insight into fabrication of low-cost TiO₂ DSSCs with high power conversion efficiency.     

生物质C-N-P自掺杂TiO_2的合成及其对亚甲基兰的光催化降解活性

采用溶胶-超声辐照技术同步合成了生物质C-N-P自掺杂TiO_2复合催化剂,通过X射线光电子能谱(XPS)、X射线衍射(XRD)、扫描电子显微镜(FESEM)、紫外-可见漫反射光谱(UV-Vis-DRS)及光致发光光谱(PL)对样品进行了表征.以亚甲基兰(MB)为目标污染物,研究了C-N-P共掺杂TiO_2的可见光光催化性能.实验结果表明,在可见光照射下,光催化反应时间为2 h时,C-N-P共掺杂TiO_2复合催化剂对亚甲基兰的降解效率最高可达9 8.5%;相比纯TiO_2,C-N-P共掺杂TiO_2复合催化剂的比表面积增大,吸收边带红移,禁带宽度减小,相变温度升高,光生载流子复合率降低.     

One-step synthesis of nanocrystalline N-doped TiO2 powders and their photocatalytic activity under visible light irradiation

Nanocrystalline N-doped TiO₂ powders were successfully prepared by hydrothermal reaction for 2 h at low temperature (120 °C) and at an applied pressure of 3 MPa. The grain size of the powders (calculated by use of Scherrer’s method) ranged from 8.2 to 10.2 nm. The BET specific surface area ranged from 151.0 to 220.0 m²/g. A significant shift of the light absorption edge toward the visible light zone was observed in the UV–visible spectra. XPS results showed that nitrogen atoms were incorporated into the TiO₂ lattice. The photocatalytic activity of the synthesized N-doped TiO₂ powders was evaluated by measurement of photodegradation of methylene blue (MB) in aqueous solution under visible light irradiation. The amount of MB degraded increased with increasing illumination intensity.     

Photocatalytic Activity for Water Decomposition to Hydrogen over Nitrogen‐doped TiO2 Nanoparticle

Nitrogen-doped TiO2 nanoparticle photocatalysts were obtained by an annealing method with gaseous ammonia and nitrogen. The influence of dopant N on the crystal structure was characterized by XRD, XPS, BET, TEM and UV-Vis spectra. The results of XRD indicate that, the crystal phase transforms from anatase to rutile structure gradually with increase of annealing temperature from 300 to 700 ℃. XPS studies indicate that the nitrogen atom enters the TiO2 lattice and occupies the position of oxygen atom. Agglomeration of particles is found in TEM images after annealing. BET results show that the specific surface areas of N-doped samples from 44.61 to 38.27 m2/g are smaller than that of Degussa TiO2. UV-Vis spectra indicate that the absorption threshold shifts gradually with increase of annealing temperature, which shows absorption in the visible region. The influence of annealing condition on the photocatalytic property has been researched over water decomposition to hydrogen, indicating that nitrogen raises the photocatalytic activity for hydrogen evolution, and the modified TiO2 annealed for 2 h at 400 ℃ under gas of NH3/N2 (V/V＝1/2) mixture shows better efficiency of hydrogen evolution. Furthermore, the N-doped TiO2 nanoparticle catalysts have obvious visible light activity, evidenced by hydrogen evolution under visible light (λ＞400 nm) irradiation. However, the catalytic activity under visible light irradiation is absent for Degussa as reference and the N-doped TiO2 annealed at 700 ℃.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.