Computational study on the reactions of H2O2 on TiO2 anatase (101) and rutile (110) surfaces

This study investigates the adsorption and reactions of H(2)O(2) on TiO(2) anatase (101) and rutile (110) surfaces by first-principles calculations based on the density functional theory in conjunction with the projected augmented wave approach, using PW91, PBE, and revPBE functionals. Adsorption mechanisms of H(2)O(2) and its fragments on both surfaces are analyzed. It is found that H(2)O(2) , H(2)O, and HO preferentially adsorb at the Ti(5c) site, meanwhile HOO, O, and H preferentially adsorb at the (O(2c))(Ti(5c)), (Ti(5c))(2), and O(2c) sites, respectively. Potential energy profiles of the adsorption processes on both surfaces have been constructed using the nudged elastic band method. The two restructured surfaces, the 1/3 ML oxygen covered TiO(2) and the hydroxylated TiO(2), are produced with the H(2)O(2) dehydration and deoxidation, respectively. The formation of main products, H(2)O(g) and the 1/3 ML oxygen covered TiO(2) surface, is exothermic by 2.8 and 5.0 kcal/mol, requiring energy barriers of 0.8 and 1.1 kcal/mol on the rutile (110) and anatase (101) surface, respectively. The rate constants for the H(2)O(2) dehydration processes have been predicted to be 6.65 × 10(-27) T(4.38) exp(-0.14 kcal mol(-1)/RT) and 3.18 × 10(-23) T(5.60) exp(-2.92 kcal mol(-1)/RT) respectively, in units of cm(3) molecule(-1) s(-1).     

V2O5/TiO2-ZrO2催化剂上甲醇选择氧化制甲缩醛

采用共沉淀法制备TiO2-ZrO2复合氧化物载体、等体积浸渍法制备V2O5/TiO2-ZrO2催化剂,对催化剂在温和条件下甲醇选择氧化生成甲缩醛(DMM)反应进行研究.结果表明,与单一氧化物载体TiO2或ZrO2负载的钒基催化剂相比,V2O5/TiO2-ZrO2对甲醇选择氧化具有较好的催化性能.XRD、NH3-TPD和...     

Interface dominated high photocatalytic properties of electrostatic self-assembled Ag(2)O/TiO(2) heterostructure

Electrostatic self-assembled Ag(2)O/TiO(2) nanobelts heterostructure was synthesized via simple physical mixing of Ag(2)O nanoparticles and TiO(2) nanobelts. The morphologies and microstructures of Ag(2)O/TiO(2) nanobelt heterostructure were characterized by high resolution transmission electron microscopy. The interface dominated high UV photocatalytic activity and degraded photoluminescence strength of composite catalyst confirmed the heterostructure effect between Ag(2)O nanoparticles and TiO(2) nanobelts. X-ray photoelectron spectroscope provided direct evidence of charge transfer on the heterostructures between them.     

ZnO/TiO2复合涂层电极的制备及其光电性能

以氧化铟锡导电玻璃为基材,采用电泳沉积法制备负载型ZnO/TiO2复合涂层,经450℃后续烧结处理后,采用XRD、SEM、EDX和UV-Vis DRS对ZnO/TiO2复合涂层进行表征;在pH=7.00的磷酸盐缓冲溶液中,分别测试ZnO/TiO2复合涂层电极在紫外灯和100 W白炽灯辐照下的电化学阻抗谱、Tafel极化曲线和循环伏安等电化学性质。结果表明:ZnO以200~300 nm晶粒分散于复合涂层中,质量百分比为0.74%;ZnO/TiO2复合涂层在可见光区有一定的吸收;在可见光辐照下ZnO/TiO2复合涂层电极具有较好的光电活性,并对水的分解具有较强的光电催化活性。     

球磨法制备复合光催化剂Bi12TiO20/ZnO及其光催化性能

本文用水作为分散介质,采用球磨法掺杂一定量的Bi₁₂TiO₂₀于ZnO中制备复合光催化剂Bi₁₂TiO₂₀/ZnO. 利用UV-Vis、XRD和SEM等仪器对样品进行了分析与表征. 通过对甲基橙的氧化来研究其光催化活性. 结果表明,光催化剂Bi₁₂TiO₂₀/ZnO对甲基橙氧化的催化活性高于氧化锌的催化活性.当Bi₁₂TiO₂₀的掺杂量为0.5%(质量分数),球磨时间为12 h,焙烧温度为300℃时,光照20 min后,复合光催化剂Bi₁₂TiO₂₀/ZnO对甲基橙的降解率可达到95.2%.     

有机染料罗丹明B在复合催化剂TiO2-APS-PW11Ni作用下的光降解研究

利用自组装方式制备了多酸-有机胺-二氧化钛复合催化剂K5Ni(H2O)PW11O39-APS-TiO2(APS为(C2H5O)3SiCH2CH2CH2NH2的简称),简称为TiO2-APS-PW11Ni,通过红外(IR),紫外漫反射(UV/DRS)对其组成和结构进行了表征.并利用该催化剂光降解染料污染物罗丹明B(RB)水溶液,与纳米TiO2催化剂光降解进行对比,结果表明,染料罗丹明B在复合催化剂作用下的催化效果明显优于TiO2光催化效果,计算得降解半衰期分别为:T1/2(复合催化剂)＝6.5 min,T1/2(TiO2)＝21.2 min.     

TiO2/H2O2/超声波协同降解壬基酚聚氧乙烯醚溶液

采用经过处理的锐钛矿型TiO2作为催化剂,在H2O2存在下,以TiO2/H2O2/超声波协同降解壬基酚聚氧乙烯醚反应为模型,探讨了TiO2催化剂用量、H2O2用量、超声波功率、壬基酚聚氧乙烯醚溶液初始浓度、初始pH值对壬基酚聚氧乙烯醚降解率的影响。结果表明,在一定的超声波功率和一定的TiO2用量范围内,壬基酚聚氧乙烯醚降解率随超声波功率和TiO2用量的增大而增大,达到一定值后保持平稳;当H2O2浓度介于一定范围内,增大H2O2用量可提高壬基酚聚氧乙烯醚的降解率,但H2O2用量过多时,反而会使壬基酚聚氧乙烯醚的降解率下降;pH<5时,壬基酚聚氧乙烯醚降解效果较好,且pH值越小,降解率越高;pH>5时,降解率越来越低。TiO2/H2O2/超声波体系降解壬基酚聚氧乙烯醚产生了较强烈的协同效应,在同一时刻三者协同体系的降解率比其3种单独体系的降解率之和高出约60%;在TiO2催化剂用量0.4g/L、H2O2用量0.2g/L、超声波功率600W、降解时间120min的条件下,对初始质量浓度为80mg/L,pH=1的壬基酚聚氧乙烯醚溶液进行降解,其降解率达98%以上。     

The co-effect of Sb and Nb on the SCR performance of the V2O5/TiO2 catalyst

The effect of the Sb and Nb additives on the V(2)O(5)/TiO(2) catalyst for the selective catalytic reduction (SCR) of NO with NH(3) was investigated. The experimental results show that either Nb or Sb can improve the activity of V(2)O(5)/TiO(2) catalyst. Higher Nb loading led to higher N(2) selectivity. The co-doping of Sb and Nb showed higher improving effect than the single doping of Sb or Nb. The V(2)O(5)/TiO(2) catalyst doped with Sb and Nb had a better H(2)O resistance than the V(2)O(5)/TiO(2) catalyst. The addition of Sb and Nb also enhance the resistance of the V(2)O(5)/TiO(2) catalyst to K(2)O poisoning. The catalysts were characterized by BET, XRD, TEM, and XPS. The results showed that the active components of V, Sb, and Nb were well interacting with each other. The coexistence of Sb and Nb will enhance the redox ability and surface acidity and thus promote the SCR performance.     

具有多通道载流子分离功能的 ZnO/P25异质结构光催化氧化甲苯

甲苯是一种最常见的室内有毒挥发性有机物(VOCs),目前消除方法主要有吸附、催化燃烧和光催化氧化,其中光催化是一种最高效和经济可行的方法,能在较温和条件下将甲苯完全矿化为 CO2.作为研究最广泛的光催化剂, TiO2在应用中通常有锐钛矿(ATiO2)和金红石(RTiO2)两种物相,但单物相 TiO2的低量子产率和光生电子-空穴对的快速复合严重限制了它的应用.本文选择兼具锐钛矿和金红石两种物相的 P25为催化剂载体,通过负载少量 ZnO和构建多组分并具备多通道载流子分离功能的异质结以提高 TiO2基光催化剂的性能.
　　利用一步浸渍法制备了一系列 ZnO/P25复合光催化剂,考察了其光催化降解气相甲苯性能. X射线粉末衍射结果表明, ZnO/P25异质光催化剂是由 ATiO2, RTiO2和红锌矿三种物相结构组成.高分辨透射电镜结果表明, ZnO/P25具备三相异质结 ZnO(002)/ATiO2(101)/RTiO2(110).紫外可见光谱、荧光光谱和光电流表征结果表明, ZnO/P25所形成的三相异质结不但增强了光吸收能力,还实现了多通道电子/空穴分离.催化降解实验表明, ZnO/P25异质光催化剂能在室温紫外光辐射下将甲苯完全矿化为 CO2和 H2O.基于三相异质结和多通道光生电子-空穴对分离的形成及促进作用, ZnO/P25光催化活性和速率均明显高于 P25.本文报道的多通道载流子分离理念可为高效光催化剂设计和应用提供一种新思路.     

Preparation and characterization of porous TiO_2/ZnO composite nanofibers via electrospinning

<正>Porous TiO_2/ZnO composite nanofibers have been successfully prepared by electrospinning technique for the first time.It was generated by calcining TiO_2/ZnCl_2/PVP[PVP:polyvinyl pyrrolidone)]nanofibers,which were electrospun from a mixture solution of TiO_2,ZnCl_2 and PVP.Transmission electron microscopy(TEM) and X-ray diffraction(XRD) analyses were used to identify the morphology of the TiO_2/ZnO nanofibers and a formation of inorganic TiO_2/ZnO fibers.The porous structure of the TiO_2/ZnO fibers was characterized by N_2 adsoption/desorption isotherm.Surface photovoltage spectroscopy(SPS) and photocatalytic activity measurements revealed advance properties of the porous TiO_2/ZnO composite nanofibers and the results were compared with pure TiO_2 nanofibers,pure ZnO nanofibers and TiO_2/ZnO nanoparticles.     

CO Preferential oxidation promoted by UV irradiation in the presence of H2 over Au/TiO2

The catalytic oxidation of CO was performed over Au/TiO(2) under UV irradiation in the presence of H(2) in different reaction systems. It was found that the introduction of H(2) enhanced the CO thermocatalytic oxidation in a CO pre-introduced system (CO/O(2)vs. CO/H(2)/O(2)), but suppressed that in an O(2) pre-introduced (O(2)/CO vs. O(2)/H(2)/CO) system. Although the CO oxidation in both CO/H(2)/O(2) and O(2)/H(2)/CO systems could be remarkably enhanced under UV irradiation, the oxidation of H(2) was suppressed under UV irradiation. It was proposed that the dissociative chemisorption H ([triple bond]Ti-H) at surface oxygen vacancy sites of TiO(2) could act as both the electron-acceptors for the photogeneration electrons and the electron-donors for the chemisorbed O(2) at TiO(2), and thus enhance the CO oxidation during the coinstantaneous process of thermocatalysis and photocatalysis. The suppression of H(2) thermocatalytic oxidation under UV irradiation might be ascribed to the electron transfer effect, i.e., the dissociative chemisorption H on Au (Au-H) could be desorbed at the H(2) molecule via accepting the photogenerated electrons from TiO(2).     

氧化物担载铑原子簇催化剂的金属载体相互作用的考察——Ⅰ.Rh/V_2O_5和RH/TiO_2催化剂的金属载体强相互作用的比较

本文用XPS和XRD考察了由Rh_4(CO)_(12)出发制得的Rh/V_2O_5和Rh/TiO_2两种催化剂的金属载体强相互作用的差别。实验结果表明,1)高温H_2还原的Rh/TiO_2催化剂,经氧处理后即能恢复吸H_2能力。Rh/V_2O_5催化剂在较低温度(473K)H_2还原时Rh就进入SMSI状态,吸H_2能力被完全抑制,373K氧处理并不能使之恢复,吸H_2性质表现出不可逆性。2)与Rh/TiO_2催化剂的TiO_2相比,Rt/V_2O_5催化剂的V_2O_5更易还原,Rh对V_2O_5的还原有明显的促进作用。3)担载在TiO_2上的Rh比在V_2O_5上更易还原。4)还原后,催化剂表层的Rh/V、RH/Ti均有较大幅度的降低。用氧空位模型能较好地说明Rh/TiO_2催化剂的实验结果,而Rh/V_2O_5催化剂的实验结果适于用钒氧化物覆盖模型解释。     

Structural features of titanate nanotubes/nanobelts revealed by Raman, X-ray absorption fine structure and electron diffraction characterizations

High-purity nanotubes and nanobelts could be controllably obtained in hydrothermal treatments of anatase TiO(2) in concentrated NaOH solution depending on treating temperature and duration. Their structural features were studied employing X-ray diffraction, Raman, X-ray absorption fine structure, and electron diffraction characterizations. The results reveal that both the nanotubes and nanobelts might be of layered titanate structure. The similarity and difference among the nanotubes/nanobelts and other bulk titanates represented by trititanate H(2)Ti(3)O(7) and lepidocrocite-type H(0.7)Ti(1.825) square(0.175)O(4.0).H(2)O were also presented.     

Heterobimetallic molecular cages for the deposition of Cu/Ti and Cu/Zn mixed-metal oxides

Heterobimetallic molecular precursors [Ti4(dmae)6(mu-OH)(mu-O)6Cu6(OAc)9.H2O] (1) and [Zn7(OAc)10(mu-OH)6Cu5(dmae)4Cl4] (2) for the deposition of metal oxide thin films of Cu6Ti4O12 (Cu3TiO4, TiO2) and Cu5Zn7O12 (ZnO, CuO) were prepared by the interaction of Ti(dmae)4 with Cu(OAc)2.2H2O for 1 and tetrameric (N,N-dimethylamino)ethanolatocopper(II) chloride, [(dmae)CuCl]4 [where dmae = (N,N-dimethylamino)ethanolate] with Zn(OAc)2.2H2O (where OAc = acetate) for 2 in dry toluene. Both complexes were characterized by melting point, elemental analysis, Fourier transform IR, fast atom bombardment mass spectrometry, thermal analysis (TGA), and single-crystal X-ray diffraction. TGA and XRD prove that complexes 1 and 2 undergo facile thermal decomposition at 300 and 460 degrees C to form thin films of Cu/Ti and Cu/Zn mixed-metal oxides, respectively. Scanning electron microscopy and XRD of the thin films suggest the formation of impurity-free crystallite mixtures of Cu3TiO4 and TiO2, with average crystallite sizes of 22.2 nm from complex 1 and of ZnO and CuO with average crystallite sizes of 26.1 nm from complex 2.     

二氧化钛纳米粒子-氧化石墨烯/聚酰亚胺混合基质膜的原位聚合及气体渗透性能

以钛酸四丁酯为前驱体,采用浸渍-沉淀法制备二氧化钛纳米粒子-氧化石墨烯(TiO_2-GO)复合物,再将TiO_2-GO复合物与4,4'-(六氟异亚丙基)邻苯二甲酸酐和4,4'-二氨基二苯醚通过原位聚合构建TiO_2-GO/TiO_2-GO/PI(聚酰亚胺)混合基质膜,用于CO_2的渗透脱除.采用傅里叶变换红外光谱(FTIR)、拉曼光谱(Raman)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、热失重(TG)和Zeta电位等表征了TiO_2-GO复合物和TiO_2-GO/PI混合基质膜的形貌与结构;探讨了TiO_2掺杂量对TiO_2-GO复合物及TiO_2-GO/PI混合基质膜的结构和气体渗透性能的影响.结果表明,TiO_2-GO复合物中TiO_2纳米粒子较均匀地沉积在GO片层上,TiO_2纳米粒子在形成的同时破坏了GO的结构,使其无序度增加.TiO_2的掺杂对TiO_2-GO/PI混合基质膜的形貌与结构影响较小,但提升了TiO_2-GO/PI混合基质膜的CO_2和N2渗透性能.但过量的掺杂使TiO_2粒子在GO片层上团聚,从而导致TiO_2-GO复合物在混合基质膜中的分散性变差,CO_2渗透性及CO_2/N2渗透选择性降低.当TiO_2掺杂质量分数为30%时,TiO_2-GO/PI混合基质膜的CO_2渗透性为360 Barrer[1 Barrer=10~(-10)cm~3(STP)·cm/(cm~2·s·cm Hg)=7.5×10~(-14)cm~3(STP)·cm/(cm~2·s·Pa)],CO_2/N_2的渗透选择性可达31.     

TiO2与ZnO复合纳米结构电极的光电化学研究

利用尿素加压共沉淀法以Ti(SO4)2与Zn(NO3)2为原料制备了TiO2-ZnO复合纳米粒子, 其纳米结构电极的光电化学研究结果表明, 反应物摩尔比为3∶1, 于530 ℃煅烧制备的复合纳米结构电极的光电转换效率最高. 对吸附染料RuL2(SCN)2∶2TBA的纳米结构TiO2和各种复合纳米粒子的纳米结构电极进行光电研究的结果表明, 染料对各纳米结构电极都起到了敏化作用, 其中也是由反应物摩尔比为3∶1, 于530 ℃煅烧制备的纳米结构电极的光电转换效率最高. 对聚3-甲基噻吩修饰的纳米结构TiO2和摩尔比为3∶1, 于530 ℃煅烧的复合纳米粒子构成的纳米结构电极进行光电性能研究, 结果表明, 聚3-甲基噻吩与半导体纳米粒子之间存在p-n结, 在一定条件下p-n结的存在有利于光生电子/空穴的分离, 从而提高了光电转化效率.     

纳米微晶TiO2合成Li4Ti5O12及其嵌锂行为

用溶胶-凝胶法并经热处理制备不同形态和晶体尺寸的TiO2，分别与Li2CO3高温固相反应生成锂钛复合氧化物，经电化学测试发现,用300 ℃热处理所得纳米微晶TiO2制备的Li4Ti5O12具有良好的嵌锂性能，其可逆比容量大于95 mA•h•g－1，充放电效率近100％，循环性能良好，电压平台平稳,在嵌锂至容量≥85％或脱锂至容量≥90％时均有明显的电压变化，可用作锂离子电池负极材料.     

H2O2/TiO2超声协同光降解活性艳橙的研究

以活性艳橙溶液为模拟废水,通过H₂O₂/TiO₂超声(US)协同作用光降解活性艳橙溶液,探讨了TiO₂催化剂用量、H₂O₂用量、活性艳橙溶液的初始浓度、pH值、TiO₂催化剂锻烧温度等对活性艳橙溶液降解率的影响,并比较了几种不同作用方式对活性艳橙溶液的降解效果.结果表明:UV/H₂O₂/TiO₂/US协同作用降解活性艳橙溶液的效果最好;当活性艳橙溶液的初始浓度为20 mg·L^-1,pH＝5,TiO₂用量为0.4 g·L^-1,H₂O₂用量为0.4 ml·L^-1时,降解率可达92.06%.     

氨法选择性还原氮氧化物 V2O5/TiO2-PILC催化剂的抗硫性能

选择性催化还原(SCR)是目前去除氮氧化物最有效的方法之一. V2O5/TiO2催化剂被广泛应用于氨法选择性还原氮氧化物(NH3-SCR)反应,但该催化剂存在工作温度高(300–400oC)及 SO2氧化率高引起设备腐蚀和管路堵塞等问题,开发低温 SCR催化剂具有重要意义.过渡金属氧化物(如 Fe2O3, MnOx和 CuO等)催化剂用于低温SCR先后见诸文献报道,但这些催化剂在 SO2和 H2O存在下易失活.近年来柱撑黏土(PILC)引起科学家广泛关注, Yang等首次将 V2O5/TiO2-PILC催化剂应用于 NH3-SCR反应,发现其催化活性高于传统 V2O5/TiO2催化剂.柱撑黏土基催化剂在 NH3-SCR反应中也显示出良好抗硫性能,但 V2O5/TiO2-PILC催化剂的抗硫机理至今尚未见深入研究.因此我们制备了一系列 V2O5/TiO2-PILC催化剂,采用原位漫反射红外等方法详细研究了其抗硫性能较好的原因.
　　首先采用离子交换法制备出 TiO2-PILC载体,之后采用浸渍法制备了不同钒含量(质量分数x/%=0,3,4,5)的xV2O5/TiO2-PILC催化剂.同时,制备了传统 V2O5/TiO2和 V2O5-MoO3/TiO2催化剂作为对比.活性评价结果显示,4V/TiO2-PILC催化剂具有最高的催化活性,其催化性能与传统钒钛催化剂相当.在160oC时, NO转化率可达80%以上.同时,4V/TiO2-PILC催化剂还具有较宽的反应温度窗口,在260–500oC范围内, NO转化率保持在90%以上.向反应体系中加入0.05% SO2和10% H2O后,在低温(160oC以下)时所有催化剂的反应活性都有一定提高,可能是由于 SO2的加入提高了催化剂的表面酸性.继续升高温度,4V/TiO2和4V6Mo/TiO2催化剂活性均明显下降,而4V/TiO2-PILC催化剂的活性则未出现明显下降.原位漫反射红外光谱结果显示, SO2在三种催化剂表面的吸附以表面硫酸盐或亚硫酸盐物种以及离子态 SO42–物种形式存在,而在4V/TiO2-PILC催化剂表面离子态 SO42–物种的量最少. X射线光电子能谱及 O2程序升温脱附结果显示,在4V/TiO2-PILC催化剂上,表面吸附氧(Oads)的量最少.综合上述分析可以得出,在 SO2气氛下,离子态 SO42–物种在 SCR催化剂表面的累积可能是导致其失活的主要原因,而离子态 SO42–物种的形成可能与催化剂表面吸附氧的量有关.     

Synthesis and formation mechanism of TiO2/Al2O3 nanobelts by electrospinning

Poly(vinyl pyrrolidone) (PVP)/[Ti(SO₄)₂ + Al(NO₃)₃] composite nanobelts were prepared via electrospinning technology, and TiO₂/Al₂O₃ nanobelts were fabricated by calcination of the prepared composite nanobelts. The samples were characterized by thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). XRD results show that the composite nanobelts were amorphous in structure, and pure phase TiO₂/Al₂O₃ nanobelts were obtained by calcination of the relevant composite nanobelts at 950°C for 8 h. SEM analysis indicates that the surface of as-prepared composite nanobelts was smooth, the widths of the composite fibers were in narrow range, and the mean width was ca. 8.9 ± 2.1 μm, thickness was about 255 nm, and there is no cross-linking among nanobelts. The width of TiO₂/Al₂O₃ nanobelts was ca. 1.3 ± 0.1 μm and the thickness was about 105 nm. TG-DTA analysis reveals that the N,N-dimethylformamide (DMF), organic compounds and inorganic salts in the composite nanobelts were decomposed and volatilized totally, and the weight of the sample kept constant when sintering temperature was above 900°C, and the total weight loss percentage was 81%. FTIR analysis manifests that crystalline TiO₂/Al₂O₃ nanobelts were formed at 950°C. The possible formation mechanism of the TiO₂/Al₂O₃ nanobelts was preliminarily discussed.