Synthesis and characterization of Pt-MoO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>-TiO<Subscript>2</Subscript> electrodes for direct ethanol fuel cells

To enhance the CO-tolerance performance of anode catalysts for direct ethanol fuel cells, carbon nanotubes were modified by titanium dioxide (donated as CNTs@TiO₂) and subsequently served as the support for the preparation of Pt/CNTs@TiO₂ and Pt-Mo/CNTs@TiO₂ electrocatalysts via a UV-photoreduction method. The physicochemical characterizations of the catalysts were carried out by using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy of adsorbed probe ammonia molecules. The electrocatalytic properties of the catalysts for methanol oxidation were investigated by the cyclic voltammetry technique. The results show that Pt-Mo/CNTs@TiO₂ electrode exhibits the highest performance in all the electrodes. It is explained that, the structure, the oxidation states, and the acid-base properties of the catalysts are influenced due to the strong interaction between Ti and Mo species by adding TiO₂ and MoO _x to the Pt-based catalysts.     

Synthesis of SnO2TiO2 nanocomposite photocatalysts by supercritical fluid combination technology

Acrylic acid, acrylic ester and their ramification have developed quickly in recent years. However, their pro duction process produces a mass of waste water, which when released into the aquatic ecosystem, becomes a source of dramatic disturbance of aquat…     

Synthesis and characterization of Pt-MoOx-TiO2 electrodes for direct ethanol fuel cells

To enhance the CO-tolerance performance of anode catalysts for direct ethanol fuel cells,carbon nanotubes were modified by titanium dioxide (donated as CNTs@TiO2) and subsequently served as the support for the preparation of Pt/CNTs@TiO2 and Pt-Mo/CNTs@TiO2 electrocatalysts via a UV-photoreduction method.The physicochemical characterizations of the catalysts were carried out by using X-ray diffraction (XRD),transmission electron microscopy (TEM),X-ray photoelectron spectroscopy (XPS),and infrared spectroscopy of adsorbed probe ammonia molecules.The electrocatalytic properties of the catalysts for methanol oxidation were investigated by the cyclic voltammetry technique.The results show that Pt-Mo/CNTs@TiO2 electrode exhibits the highest performance in all the electrodes.It is explained that,the structure,the oxidation states,and the acid-base properties of the catalysts are influenced due to the strong interaction between Ti and Mo species by adding TiO2 and MoOx to the Pt-based catalysts.     

CdS光化学修饰介孔TiO2及其增强的可见光催化活性

[目的]提高介孔TiO₂材料的光催化活性。[方法]采用蒸发诱导自组装法(EISA),以四氯化钛和钛酸丁酯为钛源,嵌段共聚物P123(EO₂₀PO₇₀EO₂₀)为模板剂,制备介孔TiO₂。用光化学修饰法将CdS掺进介孔TiO₂中,合成对可见光有较好响应的复合材料,并利用X射线衍射(XRD)、透射电镜(TEM)、原子吸收分光光度法(AAS)和光催化等手段对样品进行表征。[结果]XRD和TEM结果表明成功合成有序的六方介孔材料;AAS确定复合材料中Cd的含量为0.96mg/g;光催化于500 W氙灯下以2×10^-5mol/L次甲基蓝(MB)为模型污染物,结果显示CdS/TiO₂复合材料的可见光催化活性明显提高。[结论]光化学修饰法制备的介孔CdS/TiO₂复合材料可增强其可见光催化活性。     

Preparation of polypropylene/montmorillonite nanocomposites by intercalative polymerization： Effect of in situ polymer matrix functionalization on the stability of the nanocomposite structure

The copolymerization of propylene and 5-hexenyl-9-borabicyclo[3.3.1]nonane (5-hexenyl-9-BBN) has been conducted with an MgCl2/TiCl4 catalyst intercalated in an organically modified montmorillonite (OMMT) with triethylaluminum (AlEt3) cocatalyst and diphenyldimethoxysilane (DDS) external donor. This polymerization process simultaneously results in both the exfoliation of MMT layers to realize the preparation of polypropylene (PP)/MMT nanocomposites and the implantation of reactive borane groups in the formed PP matrix. The polymer-borne borane groups have been able to undergo an effi-cient hydrolysis process under very mild reaction conditions (40℃, 3 h, in THF), introducing hydroxy groups into PP without sacrificing the polymerization-formed nanocomposite structure (the exfoliation of MMT). The resultant hydroxyl-functionalized PP/MMT nanocomposites exhibit enhanced structural stability against processing compared with those based on unfunctionalized PP matrix.     

Synthesis, structure and ethylene polymerization behavior of titanium complexes [C3H6（N = CH-Ar-O）2]TiCl2

Early transition metal catalysts containing twophenoxy-imine ligands, called FI catalysts which havevery high potential to become a new generation of olefinpolymerization catalysts, are new-type catalysts whichhave attracted much attention in recent years[1—3]. Many ofthem display activities comparable to those of the metal-locene catalysts and, in some cases, behave as living po-lymerization catalysts of α-olefins. Brookhart and Gibsonet al.[4,5] recently reported separately series of Schi…     

In situ time-resolved FTIR investigation on the reaction mechanism of partial oxidation of methane to syngas over supported Rh and Ru catalysts

In situ time-resolved FTIR spectroscopy was used to study the reaction mechanism of partial oxidation of methane (POM) to synthesis gas and the reaction of CH₄/O₂/He (2/1/45, molar ratio) gas mixture with adsorbed CO species over Rh/SiO₂, Ru/γ-Al₂O₃ and Ru/SiO₂ catalysts at 500—600℃. It was found that CO is the primary product of POM reaction over reduced and working state Rh/SiO₂ catalysts. Direct oxidation of CH₄ is the main pathway of synthesis gas formation over Rh/SiO₂ catalyst. CO₂ is the primary product of POM over Ru/γ-Al₂O₃ and Ru/SiO₂ catalysts. The dominant reaction pathway for synthesis gas formation over Ru/γ-Al₂O₃ catalyst is via the reforming reactions of CH₄ with CO₂ and H₂O. For the POM reaction over Rh/SiO₂ and Ru/γ-Al₂O₃ catalysts, consecutive oxidation of surface CO species is an important pathway of CO₂ formation.     

Ti-Si复合氧化物催化剂的合成、 表征及邻苯二酚O-单醚化反应性能

采用溶胶-凝胶法制备了不同Ti/Si比的钛硅氧化物及纯SiO₂和TiO₂样品, 通过XRD, FT-IR, UV-vis, NH₃-TPD和氮吸附等手段对材料的物理化学性质进行了表征. 结果表明, Ti-Si复合氧化物以无定形状态存在, 随着硅量的增加, 钛的存在形态由六配位为主向四配位为主转变, 表面酸量降低; 样品在以邻苯二酚和甲醇为原料气相法合成愈创木酚反应中的活性结果表明, n(Ti) ∶n(Si)＝6 ∶1的样品活性最高68％, 随着Ti/Si的减小活性降低, 这可能与样品表面酸量和酸类型变化有关.     

Ti-M分子筛合成及其性能研究

 以高硅丝光沸石(M分子筛),TiO₂粉和HClO₄为原料,水热晶化法合成Ti-M分子筛.运用FT-IR和UV-vis光谱技术表征合成的Ti-M分子筛样品的物化特性,证明了钛原子进入了M分子筛的骨架位,推测出骨架钛在Ti-M分子筛中的确存在.选择环已酮氨氧化为探针反应,考察了Ti-M对此反应的催化活性,结果表明Ti-M分子筛对环已酮氨氧化具有较好的催化性能.     

纳米Pt-Ru/C电催化剂的制备

以炭黑（Vulcan XC72)为载体，将铂钌混合氧化物胶体吸附在炭黑上，然后用氢气还原以制备Pt-Ru/C电催化剂，利用X－射线衍射（XRD）经及X－射线能谱（XPS）技术对样品进行表征，结果表明：在Pt-Ru/C中，面心立方结构中的部分铂原子被钌原子取代，铂钌合金原子的粒子大小在3nm左右，铂钌氧化物吸附在炭黑上后，两种金属的氧化态降低，可以通过氢气鼓泡的方法将其还原。     

Microstru cture and oxygen storage capacity of Sr-modified Pt/CeO2 –ZrO2catalysts

Strontium was introduced into CeO2–ZrO2 mixed oxides (CZ) by doping and impreg-nation metho ds, and then Pt was impregnated on the Sr-modifie d CZ to obtain the catalysts. X-ray diffraction (XRD), X-photon spectra (XPS), high-resolution transmission electronic microscopy (HRTEM) and H2 temperature programmed reduction (TPR) were carried out to characterize the micro-structure and reducibility of catalysts. The oxygen storage capacity (OSC) was evaluated with CO serving as probe gas. The results showed that the incorporation of Sr₂₊ in the lattice of CZ could promote the OSC properties by increasing the structure defects and enhancing the diffusion rate of oxygen from bulk to surface. For the Sr-impregnated sample, the strong metal–support interaction (SMSI) between Pt and CZ was interrupted, since Sr covered parti al surface Ce species. Such interruption retarded the back-spillover effect occurring at the Pt/Ce interface at low temperature, resulting in the loss of OSC. Meanwhile, it was found that a part of impregnated Sr₂₊ could partially diffuse from the surface to the inner atomic layers of CZ and partially incorporated in the lattice during the calcination. The OSC performance of Sr-impregnated sample therefore climbed remarkably with the rise of temperature.     

共沉淀法原位合成TiB_2/B_4C陶瓷复合粉体

采用共沉淀技术,以TiCl4溶液和B4C粉末为主要原料原位合成了TiB2/B4C陶瓷复合粉体.利用TEM研究了溶液的pH值和氨水滴定速度对Ti(OH)4包覆B4C效果的影响,利用X射线衍射仪研究了合成温度对陶瓷复合粉体物相的影响,并分析了TiB2/B4C陶瓷复合粉体的合成热力学.实验结果表明:当溶液的pH值为5,氨水的滴定速度为2 mL/min时,Ti(OH)4包覆B4C效果最佳,当合成温度高于1 350℃时,可以合成出TiB2/B4C陶瓷复合粉体.     

Simulation for the primary electronic donor of photosystem IIin vitro

Histidine coordinated to Chi a is a distinct characteristic of Chl ain vivo. By using histidine analogue of 1-methylimidazole (C₄H₆N₂2) and measuring the UV/vis absorption, CD and MCD spectra of the interaction between C₄H₆N₂ and Chl a in CCI₄, we have obtained that: (i) In pure CCl₄ solvent, Chl a molecule is in five-coordinate state, and two Chl a molecules form an asymmetric compact-dimer with strong coupling interaction. We propose that the two Chl a molecules are connected by two unequally coordinated Mg-O bonds (the two oxygen atoms come from the C=O of C13¹ keto and C17 ester, respectively); (ii) when the molar ratio of C₄H₆N₂/Chl a is 0.5 or 1 (corresponding to 2Chl a · 1C₄H₆N₂ and 2Chl a · 2C₄H₆N₂, respectively), significant changes have been observed in the absorption, CD and MCD spectra, which indicate that the Chl a remains in dimer form, but the coupling interaction between them reduces greatly. We postulate that C₄H₆N₂ replaces the ligation of C=O of C17 ester and C13¹ keto to Mg atoms sequentially. The two Chl a molecules linked by two weakly interacted Mg…O bonds form a relaxed-dimer. The structure of the model is essentially similar to that of the primary electronic donor, P₆₈₀, of photosystem II in high plants and algae.     

CuO/CeO2催化剂在温度变动过程中的CO-PROX催化性能

采用浸渍方法制备不同Cu/Ce原子比的CuO/CeO₂催化剂,用于富氢气体中CO优先氧化反应(CO-PROX),考察其在温度变动情况下的催化性能. 利用X射线衍射(XRD)、程序升温还原(TPR)方法对反应前后催化剂样品进行了表征. XRD测试表明,催化反应后的催化剂中有金属Cu0生成. 这与文献结果一致. 与不含CO₂的情况比较,当模拟富氢气体中含有CO₂时,低温段催化活性明显下降. Cu/Ce原子比为10%的催化剂在温度变动过程中具有较稳定的催化性能.      

不同形貌LaBO_3型钙钛矿的制备及其催化H_2O_2分解反应性能

采用柠檬酸络合法制备了La BO3(B=Fe,Co,Ni)钙钛矿催化剂,通过X-射线粉末衍射(XRD)、傅立叶-红外光谱(FT-IR)、透射电镜(TEM)、X-射线光电子能谱(XPS)等对催化剂进行了表征,在室温下测定了其对H2O2的催化分解能力.结果表明:催化分解能力依次为La Ni O3>La Co O3>La Fe O3,说明Ni较Co和Fe能更好地分解H2O2.通过改变La Fe O3催化剂的形貌也能提高催化剂性能,如多孔状La Fe O3较负载在SBA-15上的La Fe O3具有更好的催化分解活性.     

Mechanochemical preparation of sulfur-doped nanosized TiO2 and its photocatalytic activity under visible light

In order to make nanosized TiO2 photocatalyst responsive to visible light and effectively utilize solar energy, we have, for the first time, prepared S-doped nanosized TiO2 by a mechanochemical method with hydrolysis of TiCl4. The as-prepared S-doped nanosized TiO2 possesses strong absorption for visible light of 400-650 nm and shows high photocatalytic activity for decomposition of methylene blue under irradiation of visible light. The oxidation states of the S atoms incorporated into TiO2 were determined to be S^6＋ and S^4＋. The comparative study of fluorescence emission spectra shows that S-doping has also improved the separation of electron-hole pairs.     

Etching mechanism of barium strontium titanate （BST） thin films in CHF_3/Ar plasma

Reactive ion etching was used to etch barium strontium titanate thin films in a CHF3/Ar plasma.BST surfaces before and after etching were analyzed by X-ray photoelectron spectroscopy to investigate the reaction ion etching mechanism,and chemical reactions had occurred between the F plasma and the Ba,Sr and Ti metal species.Fluorides of these metals were formed and remained on the surface during the etching process.Ti was almost completely removed because the TiF4 by-product is volatile.Minor quantities of Ti?F could still be detected by narrow scan X-ray photoelectron spectra,and Ti?F was thought to be present in the form of a metal-oxy-fluoride.These species were investigated from O1s spectra,and a fluoride-rich surface was formed during etching.BaF2 and SrF2 residues were difficult to remove because of their high boiling point.The etching rate was limited to 12.86 nm/min.C?F polymers were not found on the surface,indicating that the removal of BaF2 and SrF2 was important for further etching.A 1-min Ar/15 plasma physical sputtering was carried out for every 4 min of surface etching,which effectively removed remaining surface residue.Sequential chemical reaction and sputtered etching is an effective etching method for barium strontium titanate films.     

Ice core dust particulate by XPS-SEM/EDAX

The ice core dust particulate sampled from Mt. Xixabangma has been analyzed by means of X-ray photoelectron spectrometer (XPS) and scanning electron microscope with energy dispersion X-ray analysis (SEM/EDAX). The results show that the contents of SO ₄ ²⁻ and SO ₄ ²⁻ in the surface layer of the dust are significantly higher than those in the subsurface layer (with the exception of organic sulfide). This difference indicates that the surface SO_x has been captured and then chemically converted by the atmospheric dust particulate before its deposition with snow, which is obviously different from those inner layer sulfates and sulfites contained by dust itself. In addition, it has been determined by SEM/EDAX that the dust contains relatively high concentrations of transition metal elements such as Fe and Ti oxides which could function as photocatalysts to the conversion of SO_x adhered on the surface of the dust, and consequently accelerate the deposition of SO_x to snow. Our research also demonstrates that the adsorptive carrying and the catalytic performance of the dust to the atmospheric SO_x are most important causes of the positive correlation between SO ₄ ²⁻ and dust concentration records in ice cores.     

The synthesis and characterization of a Co-N/C composite catalyst for the oxygen reduction reaction in acidic solution

A non-precious metal Co-N/C catalyst for the oxygen reduction reaction (ORR) was synthesized by heating a mechanical mixture of cobalt chloride, urea and acetylene black under a nitrogen atmosphere. The catalyst was characterized by XRD and XPS. The electrocatalytic activity in the ORR was evaluated by linear sweep voltammetry in 0.5 mol L⁻¹ H₂SO₄ solution. The results show that the Co-N/C catalyst aids the reduction of oxygen. The presence of elemental cobalt in the precursor allows nitrogen atoms to embed themselves in the graphite matrix to form pyridinic and graphitic type C-N structures as the ORR active sites. The effect of heat-treating temperature on the catalytic activity was also investigated. The results also show that the Co-N/C catalyst is most active when pyrolyzed at 600°C. The obtained Co-N/C catalyst loses some activity after initial exposure to the H₂SO₄ solution because of leaching, but is then stable for up to 20 h immersion. The catalyst is also stable when charged, which is supported by the cyclic voltammetry results.     

新型免疫抑制剂FTY-720的合成

分别以苯为原料, 经傅克酰基化、 还原、 酰化、 缩合、 还原羰基、 还原酯基、 去乙酰化、 成盐反应和以苯乙醇为原料, 经氯化、 傅克酰基化、 缩合、 还原羰基、 还原酯基、 去乙酰化、 成盐反应合成目标分子FTY-720, 总收率分别为17%和21%. 各关键中间体及FTY-720的结构经红外光谱、 核磁共振氢谱及碳谱、 质谱等得到确证.