In离子掺杂二氧化钛纳米管可见光催化活性的研究

采用两步预掺杂方法制备出In离子掺杂二氧化钛纳米管可见光催化剂. 可见光催化降解对氯苯酚实验证明: 掺杂In离子量为3%的TiO2纳米管可见光活性最高, 是纯TiO2纳米管的2倍以上. X射线衍射(XRD), X光电子能谱(XPS)和表面光电压谱(SPS)结果表明: 当In离子掺杂浓度较小时, In离子取代晶格Ti的位置形成InxTi1－xO2取代式掺杂结构. In离子的掺杂能级与Ti离子的3d轨道形成混合价带, 使禁带宽度变窄, 增强了可见光响应. 随着In离子掺杂浓度的增加, 同时在InxTi1－xO2纳米管表面生成In2O3, 形成InxTi1－xO2/In2O3纳米管复合结构. 该复合结构有效地增加可见光响应, 促进了光生载流子的分离, 提高了光生载流子在固/液界面参加光催化反应的利用率, 使纳米管催化剂可见光催化活性显著提高.     

氟掺杂锐钛矿型TiO2溶胶的制备、表征及催化性能

以四氯化钛为前驱物, 采用改性的沉淀-溶胶-水热晶化法制备了一种具有锐钛矿型结构的氟掺杂的二氧化钛(F-TiO₂)溶胶. 研究了氟掺杂、水热晶化的温度、时间及介质pH值对溶胶粒子的晶型和晶化度的影响. 采用XRD, TG-DTA, TEM, UV-Vis-DRS, FTIR, XPS技术及吸附、表面酸度测定手段对溶胶粒子的结构进行了表征. XRD分析结果表明: 氟的掺入可以降低水热晶化反应的温度或减少反应时间、提高粒子的晶化度, 溶胶粒子具有锐钛矿型结构; TEM分析显示: 粒子呈圆球型, 平均粒径大约为6.5 nm. XPS测定结果表明; 氟在溶胶粒子中以吸附态和结合态两种形式存在; 吸附、表面酸度及光催化活性测定表明: 与P25型TiO₂及纯TiO₂溶胶粒子相比, F-TiO₂溶胶粒子具有更大的吸附能力、更强的表面酸度及更高的光催化活性. 还从光生载流子分离效率等方面探讨了掺杂对催化剂活性影响的机理.     

二氧化钛基固体超强酸的结构及其光催化氧化性能

采用溶胶－凝胶法制备了多孔性,大比表面积的ＳＯ４＾２－／ＴｉＯ２固体超强催化剂,运用ＸＲＤ,ＢＥＴ比表面积测定,ＸＰＳ和ＵＶ－Ｖｉｓ反射光谱等技术对该催化剂的结构,表面状态以及半导体特征进行了表征,并通过ＣＨ３Ｂｒ,Ｃ６Ｈ６和Ｃ２Ｈ４等典型有机物的气相光催化氧化反应。     

TiO2晶型对Au/TiO2上光催化分解臭氧的影响

以不同晶型TiO2为载体,采用沉积-沉淀法制备了Au/TiO2光催化剂,并用紫外-可见漫反射光谱、X射线光电子能谱(XPS)和表面光电压谱(SPS)等手段进行了催化剂表征,详细考察了Ti O2晶型对Au/TiO2光催化分解臭氧活性的影响.结果表明,光催化分解臭氧的活性顺序为Au/P25>Au/Anatase>Au/Rutile,这与不同的单一Ti O2对光催化臭氧分解的活性顺序是一致的.但在TiO2上沉积金后,其对光催化臭氧的分解活性有了显著的提高.由催化剂的Au4fXPS分析发现,不同晶型Ti O2上的电荷向金簇迁移的能力有明显差异,加之载体本身对光催化臭氧分解活性不同,两者协同作用导致负载金催化剂光催化分解臭氧活性的不同.SPS信号强度与催化剂光催化活性有很好的对应关系,SPS信号越强,光生电子和空穴分离效率越高,光催化活性越好.     

Nitrogen and sulfur co-doped TiO2 nanosheets with exposed {001} facets: synthesis, characterization and visible-light photocatalytic activity

Nitrogen and sulfur co-doped TiO(2) nanosheets with exposed {001} facets (N-S-TiO(2)) were prepared by a simple mixing-calcination method using the hydrothermally prepared TiO(2) nanosheets powder as a precursor and thiourea as a dopant. The resulting samples were characterized by transmission electron microscope, X-ray diffraction, N(2) adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and UV-Vis absorption spectroscopy. The electronic properties of N,S co-doped TiO(2) were studied using the first-principle density functional theory (DFT). The photocatalytic activity of N-S-TiO(2) was evaluated by degradation of 4-chlorophenol (4-CP) aqueous solution under visible light irradiation. The production of hydroxyl radicals (˙OH) on the surface of visible-light-irradiated samples was detected by photoluminescence technique using terephthalic acid as a probe molecule. The results show that nitrogen and sulfur atoms were successfully incorporated into the lattice of TiO(2), which resulted in N-S-TiO(2) samples exhibiting stronger absorption in the UV-visible range with a red shift in the band gap transition. The first-principle DFT calculations further confirm that N and S co-dopants can induce the formation of new energy levels in the band gap, which is associated with the response of N-S-TiO(2) nanosheets to visible light irradiation. Surprisingly, pure TiO(2) nanosheets show the visible-light photocatalytic activity for the degradation of 4-CP mainly due to the substrate-surface complexation of TiO(2) and 4-CP, which results in extending absorption of titania to visible light region through ligand-to-titanium charge transfer. The N-S-TiO(2) samples studied exhibited an enhanced visible-light photocatalytic activity than pure TiO(2). Especially, the doped TiO(2) sample at the nominal weight ratio of thiourea to TiO(2) powder of 2 showed the highest photocatalytic activity, which was about twice greater than that of Degussa P25. The enhanced activity of N-S-TiO(2) can be primarily attributed to the synergetic effects of two factors including the intense absorption in the visible-light region and the exposure of highly reactive {001} facets of TiO(2) nanosheets. The former is beneficial for the photogeneration of electrons and holes participating in the photocatalytic reactions, and the latter facilitates adsorption of 4-CP molecules on the surface of TiO(2) nanosheets.     

Adsorption states of dialkyl ditelluride autooxidized monolayers on Au(111)

Organic ditellurides (R2Te2 where R = n-butyl (C4), n-octyl (C8), and n-cetyl (C16)) were synthesized, and their adsorption states after oxidation on Au(111) surfaces were studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), theoretical analyses, near-edge X-ray absorption fine structure (NEXAFS) measurements, contact angle measurements, and atomic force microscopy (AFM). The obtained results show that dialkyl ditellurides form autooxidized monolayers (AMs) on the surfaces under ambient conditions and that the oxidation process is accelerated by ambient light. XPS, UPS, and theoretical analyses suggest that the autooxidized ditelluride species consist of polymers or oligomers with Te-O-Te-O network structures stabilized by oxygen bridges between tellurium molecules following the cleavage of tellurium-gold bonds. NEXAFS and contact angle measurements indicate that the average tilt angles of the alkyl chains from the surface normal are smaller for the AMs of dialkyl ditellurides having longer alkyl chains. AFM measurements show defects and roughness features around a few angstroms in height on the surfaces of the dialkyl ditelluride AMs.     

超临界流体干燥法制备TiO2／C纳米粒子及光催化性能

以TiCl4为原料,采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO2/C复合光催化剂.以苯酚的光催化降解对所得催化剂的催化活性进行了评价.结果表明,纳米TiO2/C复合粒子与单组分TiO2比较,复合粒子光催化活性高于单组分的TiO2,h苯酚降解率高达975 ％,COD为957%.并用XRD、TEM、 UV-Vis和XPS等手段进行了表征,iO2以锐钛矿型形式存在.比较了不同制备方法制得的TiO2/C复合催化剂,得出超临界干燥法制备的光催化剂具有粒径小,比表面积大,分散性好,光催化活性高等特点.     

在玻璃的TiO2涂膜上有机物分子的吸附及光催化分解对水接触角的影响

研究了有机物分子在玻璃的TiO₂ 和WO₃/TiO₂ 复合物涂膜上的吸附及光催化分解对水接触角的影响.结果表明:有机物在空白玻璃及其膜的表面的吸附为不可逆化学吸附,WO₃/TiO₂ 复合物膜可钝化玻璃表面对大气污染物分子的吸附能力并具有较好的光催化活性.     

Adsorption and photocatalytic decomposition of amino acids in TiO2 photocatalytic systems

The adsorption and photodecomposition of seven kinds of amino acids on a TiO2 surface were investigated by zeta potential measurements and 1H NMR spectroscopy in TiO2 aqueous suspension systems. The decomposition rates increased in the order of Phe < Ala < Asp < Trp < Asn < His < Ser. For Phe, Trp, Asn, His, and Ser, the isoelectric point (IEP) of TiO2 shifted to a lower pH with increasing decomposition rates upon adsorption on TiO2, suggesting that the effective adsorption and photocatalytic sites for these amino acids should be the basic terminal OH on the solid surface. Since the amino acids that decomposed faster than the others contain -OH (Ser), -NH (Trp, His), or -NH2 (Asn) in their side chain, they are considered to interact with the basic terminal OH groups more preferably by the side chain and are vulnerable to photocatalytic oxidation. On the other hand, Ala interacts with the acidic bridged OH on TiO2 to cause an IEP shift to a higher pH. The correlation of the surface hydroxyl groups with the photocatalysis of amino acids was verified by the use of calcined TiO2 without surface hydroxyl groups.     

Adsorption and charge transfer dynamics of bi-isonicotinic acid on Au(111)

The interaction of bi-isonicotinic acid (4,4(')-dicarboxy-2,2(')-bipyridine) with the Au(111) surface has been investigated using electron spectroscopic techniques. Near edge x-ray absorption fine structure (NEXAFS) spectra show that monolayers of the molecule lie flat to the surface and also reveal that the monolayer is sensitive to the preparation conditions employed. Core level x-ray photoelectron spectroscopy (XPS) shows that the adsorbed molecule does not undergo deprotonation upon adsorption. The "core-hole clock" implementation of resonant photoemission has been used to probe the coupling between molecule and substrate. This technique has revealed the possibility of ultrafast backtransfer from the substrate into the molecule upon resonant excitation of a N 1s core level electron. This is supported by a NEXAFS and XPS investigation of energy level alignments in the system.     

Effects of thermal treatments on the recovery of adsorbed water and photocatalytic activities of TiO2 photocatalytic systems

The effects of thermal treatments on the rehydration process and photocatalytic activity were investigated by 1H NMR spectroscopy for six anatase abundant TiO2 photocatalysts with different properties. Acetic acid and benzoic acid were employed for photodecomposition in aqueous suspension. After the calcinations at 973 K, physisorbed water layers recovered relatively fast for P25, F4, and AMT-600 (shorter than 24 h) with no significant enhancement of the photocatalytic decomposition. On the other hand, for ST-01, UV-100, and AMT-100, the recovery was very slow (longer than 1 week) and only partially reversible, and the photocatalytic decomposition was considerably enhanced but retarded with rehydration. In the presence of adsorbed water, the binding of a carboxyl group of the molecules with adsorbed water is considered to compete with the direct adsorption on the surface, which reduces the amount of the direct adsorption and results in the reduction in the photocatalytic efficiency. In addition, the photocatalytic decomposition of benzoic acid with an aromatic ring was much faster in all of the TiO2 aqueous suspensions and more enhanced for the fully dehydroxylated TiO2 than that of acetic acid. These results suggest that the most efficient photocatalytic sites should be the hydrophobic sites on the TiO2 surface. The difference among the rehydration rates of different TiO2 is discussed in terms of thermally induced changes of surface morphology.     

Self-metalation of 2H-tetraphenylporphyrin on Cu(111): an x-ray spectroscopy study

The bonding and the temperature-driven metalation of 2H-tetraphenylporphyrin (2H-TPP) on the Cu(111) surface under ultrahigh vacuum conditions were investigated by a combination of x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy with density functional theory calculations. Thin films were prepared by organic molecular beam epitaxy and subsequent annealing. Our systematic study provides an understanding of the changes of the spectroscopic signature during adsorption and metalation. Specifically, we achieved a detailed peak assignment of the 2H-TPP multilayer data of the C1s and the N1s region. After annealing to 420 K both XPS and NEXAFS show the signatures of a metalloporphyrin, which indicates self-metalation at the porphyrin-substrate interface, resulting in Cu-TPP. Furthermore, for 2H-TPP monolayer samples we show how the strong influence of the copper surface is reflected in the spectroscopic signatures. Adsorption results in a strongly deformed macrocycle and a quenching of the first NEXAFS resonance in the nitrogen edge suggesting electron transfer into the LUMO. For Cu-TPP the spectroscopic data indicate a reduced interaction of first-layer molecules with the substrate as demonstrated by the relaxed macrocycle geometry.     

可循环使用的Sn-TiO2/聚噻吩纳米杂化材料用于可见光下降解有机污染物

采用改进的溶胶-凝胶法在低温制备了Sn-TiO2/聚噻吩纳米杂化材料(SPNH),运用X射线衍射(XRD)、扫描电镜、X射线光电子能谱(XPS)、红外光谱(IR)、紫外-可见光漫反射光谱(UV-DRS)和BET比表面积分析对所制样品进行了表征。 XRD结果证实聚噻吩(PTh)对TiO2晶相结构没有影响。 IR和UV-DRS结果表明,在掺杂的金属氧化物与PTh的纳米杂化和结合过程中, PTh表面与金属氧化物之间存在相互作用(类似核壳结构)。 XPS结果显示,纳米杂化材料中存在Sn4+以及PTh与TiO2各自所含的元素。催化剂表面吸附污染物结果发现, SPNH的吸附容量高于Sn-TiO2纳米粒子(STN)。在可见光下降解有机污染物硝基苯(NB)和孔雀绿(MG)的反应中, SPNH表现出比单纯STN更高的光催化活性和稳定性。由于STN上存在聚噻吩,使得样品表面吸附NB(24%)和MG(21%)的能力增加,从而导致更高的光催化收率。考察了该光催化剂在可见光下重复使用5次时的光催化活性,未见PTh的消耗和降解。这些高光催化活性的SPNH材料有望在工业水净化中用作光催化剂。     

TiO2/BiNbO4复合光催化剂的制备及降解气相苯性能

采用固相反应法制备出BiNbO4,将其与TiO2耦合,得到TiO2/BiNbO4复合光催化剂。考察了催化剂在紫外光照射下催化降解气相苯的活性。结果表明,TiO2与BiNbO4耦合后催化活性明显提高,其中36%TiO2/BiNbO4紫外光照5 h对苯的降解率是P-25的3.7倍。紫外-可见漫反射谱(UV-Vis DRS)、XRD、XPS和低温氮吸附-脱附等表征结果表明TiO2与BiNbO4的能级匹配,二者之间存在能带协同效应。耦合后的TiO2/BiNbO4的光生电子和空穴能有效分离,从而提高了催化剂催化活性。     

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。     

Structure, morphology and interface properties of ultrathin SnTTBPP(OH)2-films adsorbed on Ag(100)

The molecular interaction of dihydroxo[5,10,15,20-tetrakis(4-tert-butyl-phenyl)porphyrinato]-tin(IV) (SnTTBPP(OH)(2)), the structural order and growth of ultrathin films on Ag(100) have been studied by means of low-energy electron diffraction (LEED) and synchrotron based photoelectron spectroscopy, i.e., X-ray photoemission (XPS) and near-edge X-ray absorption fine structure (NEXAFS/XANES) spectroscopy. For the first time, monolayer adsorption of a metalloporphyrin with octahedral coordination of the metal center by two additional axial hydroxo ligands is investigated in a multi-technique study. The delicate balance of molecule-substrate interactions and intermolecular interactions leads to the formation of a densely-packed organic monolayer which is commensurate with the Ag(100) substrate. From NEXAFS linear dichroism an almost coplanar orientation of the porphyrin system is derived. XPS and NEXAFS clearly indicate that the axial hydroxo ligands are cleaved in monolayer films, i.e., upon adsorption to the Ag substrate. With increasing film thickness orientational order gets lost and leads to polycrystalline growth for thicker films as confirmed by scanning X-ray transmission microscopy (STXM).     

磁载WO3－TiO2／SiO2／Fe3O4复合光催化剂的制备及其光催化活性

 用溶胶－凝胶法在表面包覆了SiO2的磁基体Fe3O4上负载TiO2,从而得到了易于磁性固液分离的磁载WO3－TiO2／SiO2／Fe3O4复合光催化剂,并通过IR,XRD,SEM和XPS等测试手段对催化剂进行了表征．研究了磁载WO3－TiO2／SiO2／Fe3O4复合光催化剂对亚甲基蓝溶液脱色的性能,并考察了WO3掺杂量对样品催化活性的影响．结果表明,n（WO3）／n（TiO2）＝0．001时,磁载WO3－TiO2／SiO2／Fe3O4复合光催化剂的催化活性最高,循环使用3次时脱色率仍保持在98％．     

几种低碳醇在Pt／TiO2上的光催化产氢速率的研究

主要考察了无氧条件下低碳醇（甲、乙、丙醇）在Pt/TiO2表面光催化重整反应制氢。深入探讨了几种低碳醇与其放氢速率的构-效关系,提出了低碳醇在Pt/TiO2光催化剂表面吸附态的模型。     

光催化降解污染物制氢反应与原位红外表征

研究了在Pt/TiO2悬浮体系中单组分和双组分污染物为电子给体光催化分解水制氢反应. 比较了污染物甲醛、甲酸和草酸为电子给体光催化放氢反应效率，发现其活性为：草酸 >甲酸 >甲醛.原位ATR（衰减全反射）红外研究结果表明，光催化放氢活性与污染物吸附特性有关.还研究了草酸与甲酸双组分污染物体系的光解水放氢和污染物降解动力学，发现总的放氢和污染物降解速率与污染物组分在TiO2表面的吸附强度和溶液浓度有关.污染物在TiO2表面的竞争吸附决定了反应动力学.原位ATR-IR方法研究双组分混合物体系的吸附，直观地证实了上述结果.     

Controllable Fabrication of TiO(2) 1D-Nano/Micro Structures: Solid, Hollow, and Tube-in-Tube Fibers by Electrospinning and the Photocatalytic Performance

The solid, hollow, and tube-in-tube porous nanofiber structures of TiO(2) are synthesized successfully by a simple non-coaxial electrospinning method without using a complicated coaxial jet head, combined with adjusting the concentration of the TiO(2) precursor and the pinhole diameter of the jet head and by final calcination. The formation mechanisms of different structured TiO(2) fibers are discussed in detail. This method is facile and effective, and easy to scale up. Furthermore, it is a versatile method for constructing tube-in-tube fibers of other metal oxides such as ZrO(2) , SiO(2) , SnO(2) , and In(2) O(3) . The photocatalytic activity of tubular TiO(2) nanofibers for the degradation of 2-chlorophenol and 2,4-dichlorophenol under UV or visible-light irradiation is better than the one of commercial available TiO(2) powder, rutile, and anatase TiO(2) fibers.