离子液体中纳米TiO2/聚3-甲基噻吩复合膜的制备及性质研究

采用溶胶凝胶法制成了纳米TiO₂电极, 在离子液体中将其应用于3-甲基噻吩的电化学聚合, 采用循环伏安法(CV), 在线紫外可见光谱(UV-Vis), 扫描电镜(SEM)和电化学阻抗谱(EIS)对TiO₂/聚3-甲基噻吩(TiO₂/PMT)复合膜进行了表征并研究了其电化学性质. 实验证明, 不论是用循环伏安法, 恒电位, 还是恒电流方法, 都能在电极上得到聚3-甲基噻吩(PMT)膜, 并伴随有明显的掺杂和去掺杂过程. 对应的在线紫外可见光谱上, 也出现了氧化和还原两种不同的吸收状态, 还原(去掺杂)过程中在480 nm处有一个吸收峰, 而氧化(掺杂)过程中此峰消失, 取而代之的是一个可见光区的逐渐增强的吸收. PMT膜是p型半导体, TiO₂是n型半导体, 两者之间能够形成p-n异质结, 使光电转换效率得以提高. SEM给出了TiO₂电极和聚合物修饰的TiO₂的形貌图, 电极的交流阻抗谱则从一个角度说明了聚合物膜修饰电极的导电性.     

铝电极在LiNO3-KNO3熔盐中的电化学行为

采用循环伏安和恒电位电解法考察了铝电极在LiNO3-KNO3熔盐中的电化学行为. 实验结果表明, 在该熔盐中, 锂离子在铝电极上的电还原过程伴随着新生态的锂原子向电极内部的随后扩散步骤; 锂原子进入铝电极后与铝发生合金化, 形成β-LiAl合金和γ-LiAl合金; 锂离子在铝电极上的还原过程受还原态锂在铝基体内的扩散步骤控制. 循环伏安实验发现, 铝电极在该熔盐中的氧化和还原峰电流都先随循环次数增加而增大, 最后基本上趋于稳定. 这表明铝电极在该熔盐体系中具有较好的电化学稳定性.     

Reactions of 3-cyclopropyl-3-oxopropionitrile anion generated by electroreduction of 5-cyclopropylisoxazole

3-Cyclopropyl-3-oxopropionitrile anion obtained by cathodic reduction of 5-cyclopropylisoxazole in an aprotic medium was used as an example to demonstrate that cyano ketone anions show a dual reactivity. The reaction of acetyl chloride with the electrogenerated tetrabutylammonium salt of 3-cyclopropyl-3-oxopropionitrile gave O-acylation products, whereas the reaction with its sodium salt gives C-acylation products. The reactions of these salts with hydroxylamine hydrochloride follow a different route: in the case of the tetrabutylammonium salt, resinification takes place, while in the case of the sodium salt, 5-amino-3-cyclopropylisoxazole is formed. The condensation of this product with 4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dione in glacial AcOH affords 3-cyclopropyl-6-(2-thienyl)-4-(trifluoromethyl)isoxazolo[5,4-b]pyridine in 85% yield. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2110–2114, November, 2007.     

The dealkylation of 2-diethylamino-3H-phenothiazin-3-one

2-Diethylamino-3H-phenothiazin-3-one was dealkylated to 2-ethylamino-3H-phenothiazin-3-one either by photolysis or pyrolysis.

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Entalkylierung von 2-Diethylamino-3H-phenothiazin-3-on (Kurze Mitteilung)

Zusammenfassung Die Titelverbindung wurde durch Photolyse oder Pyrolyse zu 2-Ethylamino-3H-phenothiazin-3-on entalkyliert.

     

Cyclic voltammetric study on the catalysis of electrodeposited manganese oxide on the electrochemical oxygen reduction reaction (ORR) in room temperature ionic liquids (RTILs) of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF<Subscript>4</Subscript>) on glassy carbon clectrode

For the first time, the electrochemical oxygen reduction reaction (ORR), was investigated using cyclic voltammetry (CV) on the electrodeposited manganese oxide (MnO _x )-modified glassy carbon (MnO _x -GC) electrode in the room temperature ionic liquids (RTILs) of EMIBF₄, i.e. 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄). The results demonstrated that, after being modified by MnO _x on a GC electrode, the reduction peak current of oxygen was increased to some extent, while the oxidation peak current, corresponding to the oxidation of superoxide anion, i.e., O₂⁻ was attenuated in some degree, suggesting that MnO _x could catalyze ORR in RTILs of EMIBF₄, which is consistent with the results obtained in aqueous solution. To accelerate the electron transfer rate, multi-walled carbon nanotubes (MWCNTs) was modified the GC electrode, and then MnO _x was electrodeposited onto the MWCNTs-modified GC electrode to give rise to a MnO _x /MWCNTs-modified GC electrode, consequently, the improved standard rate constant, k_s, originated from the modified MWCNTs, along with the modification of electrodeposited MnO _x , showed us a satisfactory electrocatalysis for ORR in RTILs of EMIBF₄. Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 3, pp. 340–345. The article is published in the original.     

Electrocatalytic activity of poly(3-methylthiophene) electrodes

Poly 3-methylthiophene (P3MT) modified electrodes have shown an improvement for detecting catecholamines when compared to classical ones. Past work with this polymer electrode suggested the possible presence of “active sites,” which are believed to be the polymer’s center of electrocatalytic activity. The interaction of 1,5-anthroquinone-disolfonic acid (1,5-AQDS) at the P3MT electrode showed a nonreversible behavior resulting in the blocking of “the active sites,” suggesting the specific electcatalytical activity of this polymer is limited to catechol and similar compounds. In order to improve catecholamine detection, two methods of electropolymerization for P3MT were compared under similar conditions; (1) a constant potential for a specific length of time, and (2) potential cycling. It was found that cycling provided a more sensitive CV, i.e. increased number of active sites. Under a controlled pH study (pH range 2–9), the polymer electrode maintained its superior performance, manifested as lower ΔE and higher i, toward catechol over the traditional electrodes. Two different supporting electrolytes were used, sulfate and phosphate, and it was found that in neutral or basic solutions containing phosphate, the oxidation and reduction potentials of catechol shifted to lower values. Solutions containing sulfate exhibited no shift in the oxidation potential at any pH value.     

Electrocatalytic Activities of 1,2-Naphthoquinone Modified Carbon Nanotube to the Electrochemical Oxidation of β-Nicotinamide Adenine Dinucleotide

The carbon nanotube (CNT) was functionalized with the electroactive species of 1,2-naphthoquinone (Nq) by a method of adsorption to form Nq-CNT nanocomposite. The Nq-CNT was characterized by spectroscopic techniques, for example UV-Vis, FTIR, SEM, etc., and the results showed that Nq can rapidly and effectively be adsorbed on the surface of CNT with high stability. Moreover, it was shown that the dispersion ability of CNT in aqueous solution had a significant improvement after CNT functionalized with Nq. The Nq-CNT/GC electrode was fabricated by modifying Nq-CNT nanocomposite on the GC electrode surface and its electrochemical properties were investigated by voltammetry, which indicated that CNT could improve the electrochemical behavior of Nq and greatly enhance its redox peak currents. The Nq-CNT/GC electrode exhibited a pair of well-defined and nearly symmetrical redox peaks with the formal potential of –87.3 ± 4.5 mV (vs. SCE, 0.1 M PBS, pH 7.0), which was almost independent on the scan rates. The experimental results also demonstrated that Nq and CNT could synergistically catalyze the electrochemical oxidation of NADH, and Nq-CNT exhibited a high performance with lowering the overpotential by more than 510 mV. The presented method had some advantages, such as rapid and facile CNT functionalization, easy electrode fabrication, and high electrocatalytic activity, etc.     

High purity gadolinium by the electrolysis of GdF3

The anodic overvoltage on carbon and platinum electrodes in the electrochemical production of high purity gadolinium from molten 75 LiF-25 mol% GdF₃ solutions is discussed. At the cell temperature of 840°C calciumimpregnated anodes led to the reduction of inert electrode films and to a current yield of nearly 100%.The deposited gadolinium contained 75, 22, 54 and less than 100 ppm of the interstitial elements H, N, O and C respectively; the concentrations of the highest other analysed impurities were: Si (89), Fe (15), Y (5), Zr (3), Nd (3), Tb (71), Ta (49), W (23) and Re (<3 ppm).Partly performed at the Ames Laboratory—U.S. Department of Energy.     

Electrochemical reduction of some 3-aryl-2-cyanothioacrylamide derivatives at the DME

Summary The polarographic behaviour of the title compounds is reported and discussed in acid media. The obtained data indicate that these compounds undergo a four-electron reduction. A mechanism for the electrode process atpH<7 is proposed, discussed and clarified via identification of controlled potential electrolysis (CPE) product and application of cyclic voltammetry (CV).

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Die elektrochemische Reduktion einiger 3-Aryl-2-cyanothioacrylamid-Derivate an der DME

Zusammenfassung Es wurde das polarographische Verhalten der Titelverbindungen in saurem Medium untersucht. Die erhaltenen Daten zeigen, daß diese Verbindungen eine Vierelektronenreduktion eingehen. Es wird ein Mechanismus für den Elektrodenprozess beipH<7 vorgeschlagen und diskutiert. Zur Klärung der Verhältnisse wurden die mittels kontrollierter Potential-Elektrolyse (CPE) erhaltenen Produkte identifiziert und auch cyclische Voltammetrie eingesetzt.

     

Preparation, characterization and the standard enthalpy of formation of La0.95MnO3+δ and Sm0.95MnO3+δ

Among the perovskites, the rare earth manganites find application in several electrochemical devices because of their enhanced thermodynamic stability. In this paper, we present the results obtained on the preparation and characterization of La_0.95MnO_3+δ and Sm_0.95MnO_3+δ which were prepared by the solid state and sol–gel methods. XRD characterization of the manganites indicated that the crystal structure depends on the method of preparation and heat treatments. The ratio of Mn³⁺ to Mn⁴⁺ in these samples also depended on the method of preparation and heat treatments, as indicated by thermogravimetric (TG) and temperature programmed reduction (TPR) studies in Ar + 5% H₂ atmosphere. The standard molar enthalpy of formation, which is a measure of the thermodynamic stability of these compounds were determined using an isoperibol calorimeter.     

4,5-dihydro-5,5-dimethyl-3-oxo-3H-1,2,4-triazole-1-oxide. The unpredicted azoxy-regioisomer

Summary 4,5-Dihydro-5,5-dimethyl-3-oxo-3H-1,2,4-triazole (1) is converted to the title azoxy compound4 by peroxytrifluoroacetic acid. The structure assignment of4 is based on an X-ray analysis.Ab initio calculations were employed to rationalize the reaction path leading to the triazole-1-oxide4 and not to the expected regioisomer triazole-2-oxide3.

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4,5-Dihydro-5,5-dimethyl-3-oxo-3H-1,2,4-triazol-1-oxid. Das unerwartete Regioisomere

Zusammenfassung 4,5-Dihydro-5,5-dimethyl-3-oxo-3H-1,2,4-triazol (1) wird mit Trifluorperessigsäure in die Titel-Azoxy-Verbindung4 umgewandelt. Die Strukturzuordnung von4 basiert auf einer Röntgenstrukturanalyse. Mittelsab initio-Rechnungen wird versucht zu erklären, weshalb die Reaktion zum Triazol-1-oxid4 und nicht zum erwarteten regioisomeren Triazol-2-oxid3 führt.

     

Partial electro-neutralisation of -α-p-hydroxyphenylglycine in sulphuric acid medium

In the industrial synthesis of -α-p-hydroxyphenylglycine the separation of amino acid is carried out by precipitation. During this process, a mother liquor is produced with a high salt content (2 M phosphates and sulphates) and an amino acid concentration of 0.11–0.12 M. The disposal of this mother liquor causes an environmental problem and an economic loss. The salt content of this mother liquor can be reduced in 70% of the initial by means of an electrodialysis process previously carried out by us, with only an amino acid loss of 15% of the initial. To improve and simplify this process, an electro-electrodialysis process (a membrane electrolysis process; the electrode processes and the transport process across the membrane are used) has been developed in which as a first step, the electro-neutralisation of solutions containing sulphuric acid and -α-p-hydroxyphenylglycine is studied. The sulphuric acid content is reduced to 87% of the initial, without detected loss of amino acid. The final solution is posteriorly neutralised by working up the pH of the solution for precipitating the amino acid, and a mother liquor with approximately 0.10 M -α-p-hydroxyphenylglycine and a low salt content (0.08 M Na₂SO₄) is produced. This mother liquor with low salinity can be recirculated again to a new electro-electrodialysis process.     

Characterization and Activity of MnO/γ‐Al2O3 for Hydrogenation of Methyl Benzoate to Benzaldehyde

The activities of a MnO/γ‐Al₂O₃ catalyst for the selective reduction of methyl benzoate to benzaldehyde have been studied in a continuous flow reactor. Characterization of the catalyst has been conducted by XRD, XPS, NH₃‐TPD and TPD‐IR. XRD and XPS results revealed that the steady state catalyst is mainly MnO₂/γ‐AlO₃ before reduction and MnO/γ‐Al₂O₃ after reduction. Monolayer dispersion capacity obtained by XPS method is about w (Mn)11.3% TPD‐IR results revealed that there are only L acidic centers on the catalytic surface. NH₃‐TPD determinations have verified that the catalyst with a certain number of moderate strength acidic sites is advantageous to hydrogenation of methyl benzoate to benzaldehyde.     

Adsorption of<Emphasis Type="Italic"> N</Emphasis>-dodecyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethyl-3-ammonio-1-propanesulfonate (DDAPS), a model zwitterionic surfactant,on the Au(111) electrode surface

Electrochemical measurements including cyclic voltammetry, differential capacity, and chronocoulometry have been used to characterize the adsorption behaviors of the zwitterionic surfactant N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS) on the Au(111) electrode surface. The thermodynamics of the ideally polarized electrode have been employed to determine the Gibbs excess and the Gibbs energy of adsorption. The results show that the adsorption of DDAPS has a multistate character. The first two states are observed at potentials close to zero charge. At low bulk DDAPS concentrations, it corresponds to the formation of a film of nearly flat adsorbed molecules. At higher concentrations it is converted into a hemimicellar state. The second state is formed at negative potentials and charge densities close to 0 C cm^–2. It corresponds to a film of tilted molecules oriented with the hydrocarbon tail towards the metal and the polar head toward the solution.Dedicated to Professor Zbigniew Galus on the occasion of his 70^th birthday and in recognition of his many contributions to electrochemistry.     

Kinetics of oxygen reduction on porous mixed conducting (La0.85Sr0.15)0.9MnO3 electrode by ac-impedance analysis

The oxygen reduction reaction on mixed conducting (La_0.85Sr_0.15)_0.9MnO₃ electrodes with various porosities was investigated by analysis of the ac-impedance spectra. To attain a mixed electronic/ionic conducting state of (La_0.85Sr_0.15)_0.9MnO₃ with high oxygen vacancy concentration, the electrode specimen was purposely subjected to cathodic polarisation. The ac-impedance spectrum clearly showed a straight line inclined at a constant angle of 45° to the real axis in the high-frequency range, followed by an arc in the low-frequency range, i.e. it exhibited the Gerischer behaviour. This strongly indicates that oxygen reduction on the mixed conducting electrode involves diffusion of oxygen vacancy through the electrode coupled with the electron exchange reaction between oxygen vacancies and gaseous oxygen (charge transfer reaction) at the electrode/gas interface. It was further recognised that the two-dimensional electrochemical active region for oxygen reduction extends from the origin of the three-phase boundaries (TPBs) among electrode, electrolyte and gas into the electrode/gas interface segments, which is on average approximately 0.7 to 1.1 μm in length below the electrode porosity 0.12. Based from the fact that the ac-impedance spectrum deviated more significantly from the Gerischer behaviour with increasing electrode porosity above 0.22, it is proposed that due to the increased length of TPBs, the rate of the overall oxygen reduction on the highly porous electrode is mainly determined by the charge transfer reaction at the TPBs, and the subsequent diffusion of oxygen vacancy occurs facilely through the electrode.     

The reactivity of N,N-dialkyl-N-(3-phenylsulfinyltetrahydrofuran-2-ylidene)ammonium bromide

trans-Stereoselective electrophilic cyclization of (2R*,SS*)-N, N-diisopropyl-2-phenylsulfinylpent-4-enamide under the action of bromine afforded (3R*,5S*, SS*)-N-(5-bromomethyl-3-phenylsulfinyltetrahydrofuran-2-ylidene)-N,N-diisopropylammonium bromide. Its transformations under the conditions of hydrolysis, dehydrobromination, and hydride reduction were studied. Dedicated to Academician V. A. Tartakovsky on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1485–1490, August, 2007.     

La1-xCaxMnO3纳米颗粒的制备及氧还原催化性能

本文采用溶胶凝胶法制备了一系列不同Ca含量的钙钛矿型氧化物La_1-xCa_xMnO₃(x=0~0.4)纳米颗粒, X射线粉末衍射及精修、扫描电镜表征显示其相纯度和结晶度高, 颗粒平均粒径约40 nm。在0.1 mol·L^-1 KOH水溶液中进行的氧还原电催化性能测试显示, La_0.7Ca_0.3MnO₃样品催化活性最高, 表观电子转移数接近4, 还原电流密度与Pt/C催化剂相当, 而催化稳定性优于Pt/C。进一步研究了La_1-xCa_xMnO₃样品中Mn价态、晶胞参数的改变对氧还原催化活性的影响, 结果表明当x=0.3时, 催化剂中Mn处于混合价态, Mn-O键长适中, 最有利于电催化反应。     

Electrochemical Studies of a New Iron Porphyrin Entrapped in a Propylpyridiniumsilsesquioxane Polymer Immobilized on a SiO2/Al2O3 Surface

In this work, a new porphyrin, the 5,10,15,20‐tetrakis‐(2,6‐difluoro‐3‐sulfonatophenyl) porphyrinato iron(III) chloride (denoted as FeTsP) was immobilized on SiO₂/Al₂O₃ (SiAl) coated with n‐propylpyridiniumsilsesquioxane polymer (SiPy⁺Cl^?). The FeTsP was adsorbed on SiAl/SiPyCl by an ion exchange reaction, obtaining a modified solid, SiAl/SiPy/FeTsP, where the porphyrin complex was strongly adhered. Cyclic voltammograms of the SiAl/SiPy/FeTsP carbon paste electrode showed an irreversible response, with an oxidation peak at E_pa=0.40 V and nondefined reduction peak at E_pc=0.15 V (vs. SCE). These peaks were not observed for the nonmetallated porphyrin, indicating that they probably correspond to the Fe(III)/Fe(II) process. Studies made in solutions having different pH, (between pH 2 and 9) using the modified electrode showed that the peak potentials and the current density were not affect by pH changes, indicating that the iron porphyrin is very stable and strongly entrapped in the matrix. The modified electrode presented the property to electrocatalyze the eletrooxidation of hydrazine at 0.41 V (vs. SCE), at pH 7. The potentiality of the SiAl/SiPy/FeTsP electrode as a sensor for hydrazine was evaluated by the using the chronoamperometric technique. A linear response was obtained in the concentration range between 5×10^?5 and 6×10^?4 mol L^?1 of hydrazine.     

La1-xCaxMnO3纳米颗粒的制备及氧还原催化性能

本文采用溶胶凝胶法制备了一系列不同Ca含量的钙钛矿型氧化物La1-xCaxMnO3(x=0~0.4)纳米颗粒,X射线粉末衍射及精修、扫描电镜表征显示其相纯度和结晶度高,颗粒平均粒径约40 nm。在0.1 mol.L-1KOH水溶液中进行的氧还原电催化性能测试显示,La0.7Ca0.3MnO3样品催化活性最高,表观电子转移数接近4,还原电流密度与Pt/C催化剂相当,而催化稳定性优于Pt/C。进一步研究了La1-xCaxMnO3样品中Mn价态、晶胞参数的改变对氧还原催化活性的影响,结果表明当x=0.3时,催化剂中Mn处于混合价态,Mn-O键长适中,最有利于电催化反应。     

Die Kristallstruktur von TlFe3Te3

TlFe₃Te₃ is hexagonal, space groupP6₃/m–C _2h ⁶ ,a=9.350(2) Å,c=4.2230 (7) Å,Z=2. Iron and tellurium atoms occupy the positions 6 (h) withx=0.170,y=0.149 andx=0.046,y=0.357 respectively. Thallium atoms are situated in 2 (d). The structure was determined on the basis of single crystal data obtained form a four circle diffractometer. Refinement yielded andR-value of 4.8% for an asymmetric set of 267 reflections. TlFe₃Te₃ is a new structure type. The structure and its relations to the Mn₅Si_3–, the Nb₃Te₄-and the Tl _x V₆S₈-type are discussed.