吸附在Pt/C催化剂上Eu~(3+)对CO电氧化的促进作用

引言目前影响质子交换膜燃料电池(PEMFC)迅速发展并商业化的主要问题之一是阳极催化剂抗CO的毒化能力。Pt因其对氢的氧化具有高的催化活性而广泛地用作PEMFC的阳极催化剂,也有人研究将其它金属用于PEMFC阳极催化剂,但催化活性要比Pt低得多[1~4]。而Pt作PEMFC的阳极催化剂一个问题是痕量的CO,如10~100ppm就可以使Pt催化剂中毒[5,6]。现在的PEMFC一般用高压氢作为燃料,有很大的不安全性。人们提出用两种方法来解决这个问题,一是用甲醇、甲烷或汽油现场重整制氢作燃料的方法,但用这种制氢方法制得的氢气中含有大量的CO,即使经过纯化,也会含有ppm级的CO。另一个方法是直接用小分子醇类化合物,如甲醇作燃料,被称为直接醇燃料电池(DAFC)[7~11],但醇类化合物在阳极氧化时会有中间产物,如CO的产生,容易使阳极Pt催化剂中毒。因此,研究抗CO中毒的阳极催化剂已成为PEMFC和DAFC中一个很重要的研究课题。许多文章已报道Pt与其它贵金属或过渡金属的合金催化剂,或Pt与过渡金属氧化物的复合催化剂有一定的抗CO中毒能力。如Pt鄄Ru[12~16]、Pt鄄Bi[17]、Pt鄄Sn[17~19]...

Assemble of poly(aniline-co-o-aminobenzenesulfonic acid) three-dimensional tubal net-works onto ITO electrode and its application for the direct electrochemistry and electrocatalytic behavior of cytochrome c

Stable electroactive film of poly(aniline-co-o-aminobenzenesulfonic acid) three-dimensional tubal net-works was assembled on indium oxide glass (ITO) successfully, and the cytochrome c was immobilized on the matrix by the electrostatic interactions. The adsorbed cytochrome c showed a good electrochemical activity with a pair of well-defined redox waves in pH 6.2 phosphate buffer solution, and the adsorbed protein showed more faster electron transfer rate (12.9 s(-1)) on the net-works matrix than those of on inorganic porous or even nano-materials reported recently. The immobilized cytochrome c exhibited a good electrocatalytic activity and amperometric response (2 s) for the reduction of hydrogen peroxide (H2O2). The detection limit for H2O2 was 1.5 mu M, and the linear range was from 3 mu M to 1 mM. Poly(aniline-co-o-aminobenzenesulfonic acid) three-dimensional tubal net-works was proved to be a good matrix for protein immobilization and biosensor preparation.

Surface-appropriate lipophobicity - Application in isobutene oligomerization over Teflon-modified silica-supported 12-silicotungstic acid

A series of silica-supported 12-silicotungstic acid catalysts (H4SiW12O40, abbreviated as HSiW), modified with various loadings of Teflon (HSiW/SiO2-Teflon), were prepared by an impregnation method. The surface properties of the catalysts were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), BET, infrared (IR) spectroscopy, NH3-TPD and the Drop Shape Analysis (DSA). SEM results combined with energy-dispersive X-ray (EDX) measurements of HSiW/SiO2-Teflon revealed that F-compound (Teflon) is effectively coated on the catalyst surface. The contact angles for water and oil of 50 wt% HSiW/SiO2 and HSiW/SiO2-Teflon indicate that HSiW/SiO2-Teflon catalyst enhances not only the surface hydrophobicity but also the surface lipophobicity by means of the addition of Teflon. Silica-supported 12-silicotungstic acid modified with Teflon exhibits higher C-8(=) selectivity and longer lifetime than that of silica-supported 12-silicotungstic acid in isobutene oligomerization. Thus, surface-appropriate lipophobicity of catalysts may be effective for decreasing the interaction between coke precursors and the catalyst surface and for removing deposited coke more easily.

12-钼磷酸四丁基铵杂多蓝的光化学合成表征与晶体结构

用450W高压汞灯照射H3PMo12O40·5H2O和（Bu4N）Br（TBA）的DMF（N,N-二甲基甲酰胺）溶液,合成了12-钼磷酸四丁基铵杂多蓝（Bu4N）4[PMo12O40]·2DMF·H2O,用元素分析,IR,固体漫反射电子光谱,ESR,XPS和CV等进行了表征。晶体结构分析表明,标题化合物属单斜晶系,空间群P21/c,晶胞参数a=14.124（3）,b=17.481（4）,c=22.744（5）A,β=101.66（3）°,V=5500（2）A3,C70H160Mo12N6O43P,Mr=2956.29,Z=2,Dc=1.785g/cm3,F（000）=2970,μ（MoKα）=1.412mm-1,R=0.0638,wR=0.1975。标题化合物是由4个四丁基铵阳离子、1个12-钼磷混合价杂多阴离子[PMo12O40]4-、2个DMF分子和1个水分子构成。

VUV excitation properties of LnAl(3)B(4)O(12): Re (Ln = Y, Gd; Re=Eu, Tb)

Vacuum ultraviolet excitation spectra of LnAl(3)B(4)O(12):Re (Ln = Y, Gd; Re = Eu, To), along with X-ray photoelectron spectra, were measured. The spectra are tentatively interpreted in terms of the optical properties of the rare earth ions and the band structure. It was found that there is an energy transfer from the hosts to the rare earth ions. It was also found that the top of the valence band in the Gd compound is mainly formed by the 2p levels of O2- and the 4f levels of Gd3+, and in the Y compound mainly by the 2p levels of O2-. (C) 2000 Elsevier Science Ltd. All rights reserved.

Sol-gel-derived, polishable, 1 : 12-phosphomolybdic acid-modified ceramic-carbon electrode and its electrocatalytic oxidation of ascorbic acid

Novel ceramic-carbon electrodes (CCEs) containing 1:12-phosphomolybdic acid (PMo12) were constructed by homogeneously dispersing PMo12 and graphite powder into methyltrimethoxysilane-derived gel. Peak currents for the PMo12-doped CCE were surface-controlled at lower scan rates but diffusion-controlled at higher scan rates and peak potentials shifted to the negative potential direction with increasing pH. In addition, the electrode exhibited electrocatalytic activity toward the oxidation of ascorbic acid. The PMo12-modified CCE presented good chemical and mechanical stability and good surface renewability (ten successive polishing resulted in less than 5% relative standard deviation). (C) 2000 Elsevier Science B.V. All rights reserved.

The role of redox property of La2-x(Sr,Th)(x)CuO4 +/-lambda playing in the reaction of NO decomposition and NO reduction by CO

Two systems of mixed oxides, La2-xSrxCuO4 +/- lambda (0.0 less than or equal to x less than or equal to 1.0) and La(2-x)Tn(x)CuO(4 +/-) (lambda) (0.0 less than or equal to x less than or equal to 0.4), with K2NiF4 structure were prepared. The average valence of Cu ions and oxygen nonstoichiometry (lambda) were determined by means of chemical analysis. Meanwhile, the adsorption and activation of nitrogen monoxide (NO) and the mixture of NO + CO over the mixed oxide catalysts were studied by means of mass spectrometry temperature-programmed desorption (MS-TPD). The catalytic behaviors in the reactions of direct decomposition of NO and its reduction by CO were investigated, and were discussed in relation with average valence of Cu ions, A and the activation and adsorption of reactant molecules. It has been proposed that both reactions proceed by the redox mechanism, in which the oxygen vacancies and the lower-valent Cu ions play important roles in the individual step of the redox cycle. Oxygen vacancy is more significant for NO decomposition than for NO + CO reaction. For the NO + CO reaction, the stronger implication of the lower-valent Cu ions or oxygen vacancy depends on reaction temperature and the catalytic systems (Sr- or Th-substituted). (C) 2000 Elsevier Science B.V. All rights reserved.

环戊二烯—12-钼硅杂多四丁基铵电荷转移盐的合成、表征与晶体结构

以环戊二烯与 1 2 钼硅杂多四丁基铵为原料 ,采用光化学法合成了一种新型电荷转移盐 (Bu4N) 4(C5 H6 ) [HSiMoVI11MoVO40 ]。用元素分析、IR、CV、固体漫反射电子光谱、ESR进行了表征。X 射线晶体结构测定其晶体属三斜晶系 ,空间群P1 ,晶胞参数a =1 4.347(3) ,b =1 4.42 3(3) ,c =2 7.1 5 8(5 ) ,α =96 .90 (3) ,β =1 0 4.1 8(3) ,γ =98.2 0 (3)° ,V =5 32 2 (2 ) 3,Z =2 ,Mr=2 85 5 .30 ,Dc=1 .782 g·cm-3,F(0 0 0 ) =2 86 0 ,R =0 .0 71 9,wR =0 .1 983。标题化合物由 1个环戊二烯、4个Bu4N+阳离子和 1个 [SiMoVI11MoVO40 ]4 -阴离子构成。

Electrochemical and in situ spectroelectrochemical behavior of 2,3,7,8,12,13,17,18-octakis(hexyl-thio) tetraazaporphyrin (H(2)OHTTAP) and (Zn(II)OHTTAP)

The characterization of free base porphyrin 2,3,7,8,12,13,17,18-octakis(hexyl-thio) tetraazaporphyrin (H(2)OHTTAP) and its zinc(II) complexes [Zn(II)OHTTAP] containing eight thioether groups at the beta -pyrrole positions of the macrocycle was reported. Results obtained by cyclic voltammetry and differential pulse voltammetry indicated a five-electron reduction in five steps for each complex. They were oxidized in two single-electron-transfer steps to yield pi -cation radicals and dications and reduced in three single-electron-transfer steps to yield pi -anion radicals, dianions and trianions, respectively. The redox property of H(2)OHTTAP was unusual as compared to porphyrins (PPs) and phthalocyanines (Pcs). Each process was monitored by in situ thin-layer spectroelectrochemistry, which indicated that only the Ligand was electroactive. The existence of the eight hexylthio groups was responsible for the intrastack interactions and enhanced intracolumnar and intercolumnar electron motions, resulting in improved conductivity. Copyright (C) 2001 John Wiley & Sons, Ltd.

己二胺-12-钼磷酸电荷转移盐的光化学合成与晶体结构

采用光化学法合成一种有机-无机电荷转移盐，（HMDH2）[H2PMo12O40]·AA·3H2O·DMF（HMD = 1,6-己二胺，AA = 乙醛，DMF = N,N-二甲基甲酰胺）超分子化合物。用元素分析，IR，固体漫反射电子光谱，ESR进行了表征。X-射线四圆衍射测定其晶体结构属三斜晶系，空间群 Pī，Mr=2081.68，晶胞参数a = 14.092(3)，b =14.347(3)，c =14.358(3)?，α=75.10(3)，β=80.70(3)，γ=80.73(3)°,V=2746.6(10)?3，Z=2，Dc=2.517g/cm3，F(000)=1970，μ(MoKα)=2.766mm- 1，全矩阵最小二乘法修正至R=0.0832，wR=0.2638。标题化合物是由1个质子化的1,6-己二胺、12-钼磷混合价杂多阴离子 [PMo12O40]4ˉ、3个水分子、2个乙醛分子和1个二甲基甲酰胺分子构成。

16-and 18-electron Cp*Rh complexes with 1,2-dicarba-closo-dodecabofane(12)-1,2-dichalcogenolato ligands, as studied by multinuclear magnetic resonance

The reaction of [Cp*RhCl2](2) 1 with dilithium 1,2-dicarba-closo-dodecaborane(12)-1,2-dithiolate (a) and -diselenolate (b) afforded the 16-electron rhodium(III) half-sandwich complexes Cp*Rh[E2C2(B10H10)] [E=S (3a), Se (3b)]. The 18-electron trimethylphosphane rhodium(III) half-sandwiches Cp*Rh(PMe3)[E2C2(B10H10)] 4a-c were prepared from the reaction of Cp*RhCl2(PMe3) 2 with the same dichalcogenolates, including the ditelluride (c). The complexes 4a,b could also be obtained from the reaction of 3a,b with trimethylphosphane. The molecular geometry of 4b was determined by X-ray structural analysis. The 16-electron complexes 3 an monomeric in solution as shown by multinuclear magnetic resonance (H-1-, B-11-, C-13-, P-31- Se-77-, Rh-103-, Te-125-NMR). also in comparison with the data for the trimethylphosphane analogues 4a-c and for 6a in which the rhodium bears the eta(5)-1,3-C5H3 Bu-t(2) ligand. The Rh-103 nuclear shielding is reduced by 831 ppm (3a) and 1114 ppm (3b) with respect to the 18-electron complexes 4a,b. Similarly, the Se-77 nuclear shielding in 3b is reduced by 676.4 ppm with respect to that in 4b. (C) 1999 Elsevier Science S.A. All rights reserved.

A nickel molybdenum phosphate with tunnel: Hydrothermal synthesis and structure of (NH3CH2CH2NH3)(4)center dot(NH3CH2CH2NH2)center dot Na center dot[Ni2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 6H(2)O

A nickel molybdenum phosphate, (NH3CH2CH2NH3)(4).(NH3CH2CH2NH2). Na .[Ni2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]. 6H(2)O, invoicing molybdenum present in V oxidation, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Deep brown-red crystals are formed in the triclinic system, space group P (1) over bar, a = 12,011(2), b = 14,612(3), c = 21.252(4) Angstrom, alpha = 80.54(2)degrees, beta = 83.10(2)degrees, gamma = 76.29(2)degrees, V = 3561.4(12) Angstrom(3), Z = 2, lambda(MoK alpha) = 0.71073 Angstrom (R(F) = 0.0529 for 9880 reflections), Data mere collected on a Siemens P4 diffractometer at 20 degrees C in the range of 1.75 degrees < theta < 23.02 degrees using the omega-scan technique. The structure was solved by direct methods using the program SHELXTL-93 and refined with the method of fun-matrix least-squares on F-2. The structure of the title compound may be considered to be two [Mo6O15(HPO4)(H2PO4)(3)](5-) units bonded together with a nickel atom, although several P-O groups are not protonated on account of coordination with a Na+ cation, The one-dimensional tunnels were formed in the solid of the title compound. A probe reaction of the oxidation of acetaldehyde with H2O2 using the title compound as catalyst was carried out in a liquid- solid system, showing that the title compound had high catalytic activity in the reaction, (C) 1999 Academic Press.

Gas-phase ion-molecule reactions of neutral C-60 with alkyl methyl ethers under chemical ionization conditions

Gas-phase ion-molecule reactions of buckminsterfullerene (C-60) with the ion systems generated from the self-chemical ionization of alkyl methyl ethers (CH3OR, R = n-C2H5, n-C3H7, n-C4H9) were studied in the ion source of a mass spectrometer. The adduct cation [C60C2H5O](+) and protonated molecule [C60H](+) were observed as the major products. The former adduct ion was produced by the reactions of C-60 with the methoxymethyl ion [CH3OCH2](+), and the latter resulted from the proton transfer reactions from protonated alkyl methyl ethers to C-60 It is suggested that the [3+2] cycloadduct to a 6-6 bond of C-60 (a C-C bond common to two annulated six-membered rings) is the most favorable structure among the probable isomers of [C60C2H5O](+). (C) 1998 John Wiley & Sons, Ltd.