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1.
There is a high overvoltage in the oxidation of methanol in fuel cells,and so modified electrodes are used to decrease it.A modified electrode that used Ni(II) loaded analcime zeolite to catalyze the electrooxidation of methanol in alkaline solution was proposed.Analcime zeolite was synthesized by hydrothermal synthesis,and Ni(II) ions were incorporated into the analcime structure,which was then mixed with carbon paste to prepare modified electrode.The electrocatalytic oxidation of methanol on the surface of the modified electrode in alkaline solution was investigated by cyclic voltammetry and chronoamperometry.The effects of the scan rate of the potential,concentration of methanol,and amount of zeolite were investigated.The rate constant for the catalytic reaction of methanol was 6 × 103 cm3 mol-1 s-1 from measurements using chronoamperometry.The proposed electrode significantly improved the electron transfer rate and decreased the overpotential for methanol oxidation.  相似文献   

2.
XU Xuan  PENG Qi  XIE Mei-Xiang 《结构化学》2012,31(9):1287-1294
The structures of complexes [MⅡ2Cl4L2] and [MⅢ2Cl7L]- (M = Mo, Re; L = Ph2Ppy, (Ph2P)2py) were calculated by using density functional theory (DFT) PBE0 method. Based on the optimized geometries, the natural bond orbital (NBO) analyses were carried out to study the nature of Re-Re and Mo-Mo bonds. The conclusions are as follows: the M-M distances in two-Ph2Ppy or (Ph2P)2py complexes [MⅡ2Cl4L2] are shorter than those in mono-Ph2Ppy or (Ph2P)2py complexes [MⅢ2Cl7L]- due to the double bridged N-C-P interactions. For singlet of all complexes, there is ReⅢ-ReⅢ or MoⅡ-MoⅡ quadruply bond in complex [Re2Cl7L]- or [Mo2Cl4L2], while only ReⅡ-ReⅡ or MoⅢ-MoⅢ triply bond in complex [Re2Cl4L2] or [Mo2Cl7L]-. The most stable spin state of 2 and 6, triplet, only contains triple ReⅢ-ReⅢ bond. Because the LPCl → BD*Re-Re delocalizations weaken the Re-Re bond, the distance of ReⅢ-ReⅢ quadruple bonds in [Re2Cl7L]- is slightly longer than that of ReⅡ-ReⅡ triple bonds in [Re2Cl4L2]. Moreover, due to the delocalizations from the lone pair electrons of the remaining P' atom to the M-M antibonding orbitals, the M-M distance in (Ph2P)2py complexes is slightly longer than that in Ph2Ppy complexes.  相似文献   

3.
Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide(β-Ni(OH)_2 ) was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO_2 additive on the β-Ni(OH)_2 electrode performance are examined. The structure and property of the TiO_2 added β-Ni(OH)_2 were characterized by XRD, TG-DTA and SEM analysis. A pasted–type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni(OH)_2 and TiO_2 added β-Ni(OH)_2 electrodes in 6 M KOH electrolyte. Anodic(Epa) and cathodic(Epc)peak potentials are found to decrease after the addition of TiO 2 into β-Ni(OH)_2 electrode material. Further,addition of TiO_2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni(OH)_2 lectrode,TiO_2 added β-Ni(OH)_2 electrode is found to exhibit higher proton diffusion coefficient(D) and lower charge transfer resistance. These findings suggest that the TiO_2 added β-Ni(OH)_2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.  相似文献   

4.
The density, viscosity and conductivity of ionic liquids (ILs), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]), 1-octyl-3-methylimidazolium chloride ([omim][Cl]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim] BF4]), 1-hexyl- 3-methylimidazolium chloride ([hmim][Cl]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF6]), and the [omim][BF4] + [omim][Cl], [hmim][BF4] + [hmim][Cl], and [hmim][PF6] + [hmim][Cl] binary mixtures were studied at dif- ferent temperatures. It was demonstrated that the densities of both the neat ILs and their mixtures varied linearly with temper- ature. The density sensitivity of a binary mixture is between those of the two components. The excess molar volumes (VE) of [hmim][BF4] + [hmim][Cl] and [hmim][PF6] + [hmim][Cl] mixtures are positive in the whole composition range. For [omim][BF4] + [omim][Cl], the VE is also positive in the [omim][Cl]-rich region, but is negative in the [omim][BF4]-rich re- gion. The viscosity or conductivity of a mixture is in the intermediate of those of the two neat ILs. For all the neat ILs and the binary mixtures studied, the order of conductivity is opposite to that of the viscosity. The Vogel-Tammann-Fulcher (VTF) equations can be used to fit the viscosity and conductivity of all the neat ILs and the binary mixtures. The neat ILs and their mixtures obey the Fractional Walden Rule very well, and the values of the Walden slopes are all smaller than unit, indicating obvious ion associations in the neat ILs and the binary mixtures.  相似文献   

5.
Redox and spectroscopic properties of the eight-coordination complexes of molybdenum and the rare-earth elements Eu or Er with N,N-diethyldithiocarbamate (dtc) were characterised by cyclic voltamrnetry and UV-visible absorption spectra.The complex cation [Mo(dtc)4]+ is more stable than the complex anions [Eu(dtc)4]-and [Er(dtc)4]-in redox processes,and possesses good redox reversibility.The electron transfer number,formal standard electrode potential in the redox process for the complex cation and its diffusion coefficients were obtained by in aitu spectroelectro-chemistry.  相似文献   

6.
龚静鸣  林祥钦 《中国化学》2003,21(7):761-766
Fe3O4 particles coated with acrylic copolymer (ACP) of about 5--8 nm in diameter were synthesized and used for immobilization of horseradish peroxidase (HRP). Direct electrochemistry of HRP embedded in the nanosized Fe304 solid matrix modified paraffin impregnated graphite electrode (PIGE) was achieved,which is related to the heine Fe(Ⅲ)/Fe(Ⅱ) conversion of HRP. Cyclic voltammetry gave a pair of reproducible and welldefined redox peaks at about Ea of -0.295 V vs. SCE. The standard rate constant k, was determined as 2.7 s^-1. It demonstrated that the nano-Fe3O4 solid matrix offers a friendly platform to assemble the HRP protein molecules and enhance the electron transfer rate between the HRP and the electrode. UV-Vis absorption spectra and WrIR spectra studies revealed that the embedded HRP retained its native-like structure. The HRP/Fe3O4/PIGE showed a strong catalytic activity toward H2O2. The voltammetric response was a linear function of H2O2 concentration in the range of 10-140μmol/L with detection limit of 7.3 μmol/L (s/n = 3 ). The apparent Michaelis-Menten constant is calculated to be 0.42 mmol/L.  相似文献   

7.
The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the interaction of chromium dipeptide complex ([Cr(Ⅲ)-Gly-Gly]2 ) with ninhydrin under varying conditions has been investigated. The rates of the reaction were determined in both water and surfactant micelles in the absence and presence of various organic and inorganic salts at 70 ℃ and pH 5.0. The reaction followed first- and fractional-order kinetics with respect to [Cr(Ⅲ)- Gly-Gly2 ] and [ninhydrin]. Increase in the total concentration of CTAB from 0 to 40×10-3 mol·dm-3 resulted in an increase in the pseudo-first-order rate constant (kψ) by a factor of ca 3. Quantitative kinetic analysis of kψ-[CTAB] data was performed on the basis of the pseudo-phase model of the micelles. As added salts induce structural changes in micellar systems that may modify the substrate-surfactant interactions, the effect of some inorganic (NaBr, NaCl, Na2SO4) and organic (NaBenz, NaSal, NaTos) salts on the rate was also explored. It was found that the tightly bound counterions (derived from organic salts) were the most effective.  相似文献   

8.
The effect of the addition of 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]) on the formation rates of CO2 hydrates was investigate. The isothermal and isobaric methods were used to measure the formation rates of CO2 hydrates. As compared to those of pure water, the data of phase equilibrium changed greatly. The effects of pressure, temperature, and the concentration of [C4mim][BF4] aqueous solution on the formation rates of CO2 hydrates were investigated. With a constant concentration of [C4mim][BF4], the rate of gas consumption was enhanced with the lowering of experimental temperature. However, a decrease in pressure exerted an opposite effect on the rate of gas consumption. Moreover, the addition of [C4mim][BF4] raised the equilibrium pressure of hydrate formation at the same temperature.  相似文献   

9.
The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the interaction of chromium dipeptide complex ([Cr(III)-Gly-Gly]2+) with ninhydrin under varying conditions has been investigated. The rates of the reaction were determined in both water and surfactant micelles in the absence and presence of various organic and inorganic salts at 70 ℃ and pH 5.0. The reaction followed first-and fractional-order kinetics with respect to [Cr(III)-Gly-Gly2+] and [ninhydrin]. Increase in the total concentration of CTAB from0 to 40×10-3mol·dm-3 resulted in an increase in the pseudo-first-order rate constant (kψ) by a factor of ca 3. Quantitative kinetic analysis of kψ-[CTAB] data was performed on the basis of the pseudo-phase model of the micelles. As added salts induce structural changes in micellar systems that may modify the substrate-surfactant interactions, the effect of some inorganic (NaBr, NaCl, Na2SO4) and organic (NaBenz, NaSal, NaTos) salts on the rate was also explored. It was found that the tightly bound counterions (derived fromorganic salts) were the most effective.  相似文献   

10.
The methods for preparing the H2O2 generating air (oxygen) electrode and the composite electrode of photocatalyst-TiO2/C loading on the surface of the air (oxygen) electrode were introduced.In the case of the composite electrode,the current efficiency of electro-generated H2O2 is higher than 80%(J≤15mA/cm^2).The degradation of aniline was used as an example to measure the influence of the composite electrode and compared with the system in which the air (oxygen) electrode and the photocatalyst-TiO2 were sqparated.The results confirmed that the composite electrode played an active role on accelerating the degradation rate of aniline.According to the measurement of the polarization curves of composite electrode and TiO2 photo anode,and of the adsorbing amount of aniline on the surface of the composite electrode,the principle of descending the recombination reta of photo-generated electron and hole and of enhancing the oxidation rate of organic molecule was described.The mechanism about the degradation of aniline was also discussed.  相似文献   

11.
The electrochemical behavior of ferrocene has been studied in a number of room temperature ionic liquids. Diffusion‐controlled, well‐defined anodic and cathodic peaks were found for the Fc/Fc+ (ferrocene/ferrocenium) oxidation/reduction on the gold electrode. Ohmic resistance R between working and auxiliary electrodes was deduced from impedance measurements. Cyclic voltammograms were corrected for the base line current as well as for the ohmic drop (IR). The formal potential 1/2(Epa+Epc) for ferrocene reduction/oxidation in aprotic ionic liquids tested is within a relatively narrow range and may be approximated by the value of 0.527±0.018 V (against the cryptate Ag/Ag+222 in acetonitrile reference). Ferrocene diffusion coefficients, calculated from the peak current dependence on the sweep rate, were of the order of 10?7 cm2 s?1.  相似文献   

12.
The super electron donor (SED) ability of 2-azaallyl anions has recently been discovered and applied to diverse reactivity, including transition metal-free cross-coupling and dehydrogenative cross-coupling processes. Surprisingly, the redox properties of 2-azaallyl anions and radicals have been rarely studied. Understanding the chemistry of elusive species is the key to further development. Electrochemical analysis of phenyl substituted 2-azaallyl anions revealed an oxidation wave at E1/2 or Epa = −1.6 V versus Fc/Fc+, which is ∼800 mV less than the reduction potential predicted (Epa = −2.4 V vs. Fc/Fc+) based on reactivity studies. Investigation of the kinetics of electron transfer revealed reorganization energies an order of magnitude lower than commonly employed SEDs. The electrochemical study enabled the synthetic design of the first stable, acyclic 2-azaallyl radical. These results indicate that the reorganization energy should be an important design consideration for the development of more potent organic reductants.

The super electron donor (SED) capabilities of 2-azaallyl anions has recently been discovered and applied to diverse reactivity; their structures and electron transfer characteristics are reported herein.  相似文献   

13.
Reaction of [Si(3,5‐Me2pz)4] ( 1 ) with [Cu(MeCN)4][BF4] ( 2 ) gave the mono‐ and dinuclear copper complexes [Cu2(FTp*)2] ( 3 ) and [Cu(FTp*)2] ( 4 ). Both complexes contain the so‐far unprecedented boron‐fluorinated FTp* ligand ([FB(3,5‐Me2pz)3]? with pz=pyrazolyl) originating from 1 , acting as a pyrazolyl transfer reagent, and the [BF4]? counter anion of 2 , serving as the source of the {BF} entity. The solid‐state structures as well as the NMR and EPR spectroscopic characteristics of the complexes were elaborated. Pulsed gradient spin echo (PGSE) experiments revealed that 3 retains (almost entirely) its dimeric structure in benzene, whereas dimer cleavage and formation of acetonitrile adducts, presumably [Cu(FTp*)(MeCN)], is observed in acetonitrile. The short Cu???Cu distance of 269.16 pm in the solid‐state is predicted by DFT calculations to be dictated by dispersion interactions between all atoms in the complex (the Cu?Cu dispersion contribution itself is only very small). As revealed by cyclic voltammetry studies, 3 shows an irreversible (almost quasi‐reversible at higher scan rates) oxidation process centred at Epa=?0.23 V (E01/2=?0.27 V) (vs. Fc/Fc+). Oxidation reactions on a preparative scale with one equivalent of the ferrocenium salt [Fc][BF4] (very slow reaction) or air (fast reaction) furnished blue crystals of the mononuclear copper(II) complex [Cu(FTp*)2] ( 4 ). As expected for a Jahn–Teller‐active system, the coordination sphere around copper(II) is strongly distorted towards a stretched octahedron, in accordance with EPR spectroscopic findings.  相似文献   

14.
Three organotin–oxido clusters were formed by hydrolysis of ferrocenyl‐functionalized organotin chloride precursors in the presence of NaEPh (E=S, Se). [RFcSnCl3?HCl] ( C ; RFc = CMe2CH2C(Me)?N?N?C(Me)Fc) and [SnCl6]2? formed {(RFcSnCl2)3[Sn(OH)6]}[SnCl3] ( 3 a ) and {(RFcSnCl2)3[Sn(OH)6]}[PhSeO3] ( 3 b ), bearing an unprecedented [Sn4O6] unit, in a one‐pot synthesis or stepwise through [(RFcSnCl2)2Se] ( 1 ) plus [(RFcSnCl2)SePh] ( 2 ). A one‐pot reaction starting out from FcSnCl3 gave [(FcSn)9(OH)6O8Cl5] ( 4 ), which represents the largest Fc‐decorated Sn/O cluster reported to date.  相似文献   

15.
Reaction of UV and UVI Compounds with SOCl2 UO3, UO2Cl2, UCl6, and UCl5 reacted with OSCl2 yield always UCl5 · SCl2, [SCl3]+ [UCl6]? or a mixture of these compounds, but not an adduct UCl5 · OSCl2. An X-ray study was carried out with single crystals of [SCl3]+[UCl6]?. It crystallizes in the orthorhombic space group P212121 with the lattice constants a = 1066.8, b = 1071.2, c = 1133.3 pm and with Z = 4, containing isolated pyramidal SCl3+ (rSCl = 196.2 ± 1.1 pm ?SCl2 = 102.34 ± 1.13°) and octahedral UCl6? ions (rUCl = 251.1 ± 2.6 pm).  相似文献   

16.
The interactions of [Au(cis-DACH)Cl2]Cl and [Au(cis-DACH)2]Cl3 [where cis-DACH is cis-1,2-diaminocyclohexane] with enriched KCN were carried out in CD3OD and D2O, respectively. The reaction pathways of these complexes were studied by 1H, 13C, 15N NMR, UV spectrophotometry, and electrochemistry. The kinetic data for the reaction of cyanide with [Au(cis-DACH)2]Cl3 are k = 18 M?1s?1, ?H = 11 kJ M?1, ?S = ?185 JK?1 M?1, and Ea = 13 kJ M?1 with square wave voltammetric (SWV) peak +1.35 V, whereas the kinetic data for the reaction of cyanide ion with [Au(cis-DACH)Cl2]Cl are k = 148 M?1s?1, ?H = 39 kJM?1, ?S = ?80 JK-1 M?1, and Ea = 42 kJM?1 along with SWV peak +0.82 V, indicating much higher reactivity of [Au(cis-DACH)Cl2]Cl toward cyanide than [Au(cis-DACH)2]Cl3. The interaction of these complexes with potassium cyanide resulted in an unstable [Au(13CN)4]? species which readily underwent reductive elimination reaction to generate [Au(13CN)2]? and cyanogen.  相似文献   

17.
The single crystal X-ray structure of [Pd(1)2](PF6)2 (1 = 1,4,7-trithiacyclononane) shows a crystallographically centrosymmetric cation with a distorted octahedral stereochemistry about the PdII centre with PdSeq 2.332(3) and 2.311(3) Å for the equatorial thia donors, and PdSax 2.952(4) Å for the two apically coordinated donors. The crystals have space group C2/C, with a 17.879(8), b 15.627(13), c 11.476(8) Å, β 125.92(4)° and Z = 4. Least squares refinement gave R = 0.0565 for 1153 unique observed reflections measured by counter diffracometry using Mo-Kα radiation. This green complex undergoes a chemically reversible, one-electron oxidation in CH3CN, Epa = +0.65V, Epc = +0.56 V vs. Fc/Fc+, ΔEp = 84 mV. Oxidation of [Pd(1)2](PF6)2 by controlled potential electrolysis at +0.7 V affords an orange, ESR active product which may be tentatively assigned to the corresponding palladium(III) species. These results are contrasted with data for the related homoleptic thia complexes [Pd(L)]2+ (L = 1,4,8,11-tetrathiacyclotetradecane (2), 1,4,7,10,13,16-hexathiacyclooctadecane (3)). The syntheses of the complexes cis-[Pd(1)Cl2], cis-[Pt(1)Cl2], cis-[Pd(1)(PPh3)2](PF6)2 and cis-[Pt(1)(PPh3)2](PF6)2 are also described.  相似文献   

18.
The use of the complex acid HAlCl4 (HCl+AlCl3) permits the detemrination of the standard potential of the hydrogen electrode in nitromethane. The result (E0(Hs+/H2)=0.5 V vs. Fc/Fc+, Fc=ferrocene) shows that nitromethane is very weakly basic. This measurement is confirmed by showing that the standard potential of the hydrogen electrode in various solvents is linked to Gutmann's donor numbers of these solvents. The E0(Hs+/H2) value obtained in nitromethane belongs to the correlation line.  相似文献   

19.
A nickel(II) complex, [Ni(taetacn)](ClO4)2 ? H2O, where taetacn = 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane was synthesized. The crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. The complex crystallizes in the orthorhombic space group Pna21 with a = 16.004(2) Å, b = 10.186(1) Å, c = 13.937(2) Å, V = 2271.9(5) Å3, Dx = 1.56 g cm?3, Dm = 1.59 g cm?3 (floatation method), and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values are 0.0636 and 0.1672, respectively, for all 4845 independent reflections. The compound is composed of octahedral nickel(II) cation with three 2-aminoethyl pendant groups of taetacn, tetrahedral ClO 4 ? anion, and a water molecule of crystallization. Electronic spectra are consistent with the octahedral geometry. Temperature dependence of the magnetic susceptibility (4.5–300 K) can be interpreted considering the zero-field splitting of the nickel(II) ion (g = 2.14, D = 3.72 cm?1, and = 300 × 10?6 cm3 mol?1). Cyclic voltammetry in DMF showed quasi-reversible and irreversible oxidation waves (Epa = 0.54 V, Epc = 0.45 V; Epa = 1.16 V, Epc = 0.71 V vs. Ag/Ag+).  相似文献   

20.
Ionic Structures of 4- and 5-coordinated Silicon. Novel Ionic Crystal Structures of 4- and 5-coordinated Silicon: [Me3Si(NMI)]+ Cl?, [Me2HSi(NMI)2]+ Cl?, [Me2Si(NMI)3]2+ 2 Cl?. NMI Me3SiCl forms with N-Methylimidazole (NMI) a crystalline 1:1-compound which is stable at room temperature. The X-ray single crystal investigation proves the ionic structure [Me3Si(NMI)]+Cl? 1 which is the result of the cleavage of the Si? Cl bond and the addition of an NMI-ring. The reaction of Me2HSiCl with NMI (in the molar ratio of 1:2), under cleavage of the Si? Cl bond and co-ordination of two NMI rings, yields the compound [Me2HSi(NMI)2]+Cl? 2 . The analogous reaction of Me2SiCl2 with NMI (molar ratio 2:1) leads to a compound which consists of Me2SiCl2 and NMI in the molar ratio of 1:2. During the sublimation single crystals of the compound [Me2Si(NMI)3]2+ 2 Cl?. NMI 3 are formed.  相似文献   

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