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61.
Flavio S. Damos 《Electrochimica acta》2006,51(7):1304-1312
In the present work an investigation of the effects of the electropolymerization mode on the optical properties associated to the doping/dedoping processes of nanometric films of polypyrrole (PPy) is reported, monitoring in situ and in real time using simultaneously surface plasmon resonance and electrochemical techniques (ESPR). The electropolymerization of pyrrole was performed by potentiostatic, potentiodynamic and galvanostatic methods and the use of the ESPR technique showed that the electropolymerization mode is essential to the stability of polymer and the reversibility of its optical properties during the doping and dedoping processes. Thus, the optical properties of oxidized and reduced film were obtained by nonlinear least square fitting using Fresnel equations for a four-layer system. Then, the values of the real and imaginary parts of the complex dielectric constant for PPy fims were correlated with the polymer doping level. Finally, quartz crystal microbalance measurements were also applied to obtain correlation between doping/dedoping processes and the changes in the real and imaginary parts of the dielectric constant of the polypyrrole film, showing that the doping and dedoping processes in the polypyrrole film can act directly on its optical properties while the ESPR technique can give the same information indirectly. 相似文献
62.
Anodic oxidation of mecoprop herbicide at lead dioxide 总被引:1,自引:0,他引:1
The electrochemical oxidation of an aqueous solution containing mecoprop (2-(2-methyl-4-chlorophenoxy)propionic acid) has
been studied at PbO2 anodes by cyclic voltammetry and bulk electrolysis. The influence of current density, hydrodynamic conditions, temperature
and pH on the degradation rate and current efficiency is reported. The results obtained show that the use of PbO2 leads to total mineralization of mecoprop due to the production of oxidant hydroxyl radical electrogenerated from water discharge.
The current efficiency for the electro-oxidation of mecoprop is enhanced by low current density, high recycle flow-rates and
high temperature. In contrast, the pH effect was not significant. It has also been observed that mecoprop decay kinetics follows
a pseudo-first-order reaction and the rate constant increases with rising current density. 相似文献
63.
Debasmita Das Purabi Rani Samaddar Pratik Kumar Sen Kaushik Das 《Journal of Applied Electrochemistry》2008,38(6):743-749
Galvanostatic steady state current potential measurements were carried out for oxidation of a series of aliphatic alcohols
having varying number of hydroxyl groups. The anodically deposited layer of MnO2 on platinum was used as the electrode material. The deposit was characterised by scanning electron microscopy (SEM), energy
dispersive X-ray analysis (EDAX) and electrode potential measurements. The catalytic role of MnO2 in the electro-oxidation of alcohols was indicated by the chronopotentiograms and the cyclic voltammograms. An analysis of
the electrochemical data indicated a catalytic EC mechanism in which Mn (V) is generated electrochemically and consumed chemically
in succession. Based on this and the hydrogen bonding interaction between alcoholic hydroxyl groups and MnO2 layer, a mechanism was proposed which accounts for the variation in the observed electrochemical reaction orders. Tafel behaviour
was found to be followed only approximately. Current efficiency of the electrochemical oxidation of polyols was studied. Replacement
of platinum by carbon as current collector was found to leave the electrocatalytic activity of the MnO2 deposit practically unaltered. 相似文献
64.
Teresa Łuczak 《Journal of Applied Electrochemistry》2008,38(4):469-476
The electrooxidation of phenylethanolamine (2-amino-1-phenylethanol) at a gold electrode in alkaline electrolyte has been
studied. Measurement of the differential capacitance of the electric double layer versus the electrode potential has shown
that the adsorption of phenylethanolamine at the gold-solution interface plays a significant role in the oxidation mechanism.
The effect of amine concentration, electrolyte pH and potential scan rate on the electrooxidation is analysed. 相似文献
65.
A. Demoz C. Khulbe C. Fairbridge S. Petrovic 《Journal of Applied Electrochemistry》2008,38(6):845-851
Hydrogen is among the emerging energy vectors that are being developed to replace nonrenewable hydrocarbon energy sources.
The preferred method to produce hydrogen without generating greenhouse gases is the electrolysis of water using renewable
energy. The reduction of energy during the water electrolysis process is a desirable goal regardless of the source of electric
power. Similar to ferrous/ferric mediation, iodide can be used as a mediator in the electrolysis of an acidic suspension of
coke or coal. The iodide ion is oxidized at a far lower anodic potential than the alternative oxygen evolution reaction. This
reduces the cell electrolysis voltage and, consequently, reduces electricity use. The iodide consumed at the anode is continuously
regenerated by chemical reaction with the coke/coal in suspension. 相似文献
66.
1,3,5‐Triglyceratetriazine [first tier (G1)] and tri(1,3,5‐triglycerate) triazine [second tier (G2)] dendrimers were prepared with 1,3,5‐trichlorotriazine and sodium glycerate in a 1 : 3 mass ratio in an ethanolic medium.G1 and G2 were amorphous, white, solid substances. Their structures were elucidated with IR, 1H‐NMR, and 13C‐NMR, and their thermal stability was studied with thermogravimetric analysis. The activation energy was calculated with the Freeman–Carroll model. Densities, viscosities, and surface tensions for 0.01–0.08 mol/kg aqueous solutions increased at 0.01 mol/kg for sodium glycerate, 1,3,5‐trichlorotriazine, 1,3,5‐triazine triglycerate chloride, G1, and G2. These values were measured at 298.15 K. The apparent molal volume, reduced viscosity, and inherent viscosity were calculated from the densities and viscosities, respectively. The data were regressed for the limiting densities, limiting apparent molal volumes, intrinsic viscosities, limiting inherent viscosities, and limiting surface tensions for solute–solvent interactions. The positive limiting apparent molal volume values were noted in the order of G2 > 1,3,5‐triazine triglycerate chloride > G1 > 1,3,5‐trichlorotriazine > sodium glycerate, with weaker hydrophilic intermolecular interactions of G2. The higher intrinsic viscosity and limiting inherent viscosity values for G2 implied stronger G2–H2O hydrophilic interactions, and the higher limiting apparent molal volume of G2 indicated slightly higher dynamic conformational changes in comparison with G1, with stronger structural activities. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
67.
The swelling kinetics curves of structurally defined poly(acrylic acid) hydrogel in bidistilled water at temperatures: 25, 30, 35, 40, and 45°C were determined. The possibility of kinetically explaining the isothermal swelling process by applying the following models: reaction controlled by diffusion, first order chemical reaction kinetics, and second order chemical reaction kinetics, was investigated. It was found that kinetically explaining the swelling process using these methods was limited to only certain parts of the process. The swelling process in bidistilled water was described in full range assuming that the hydrogel's swelling rate was a kinetically controlled reaction by the rate of the movement of reactive interface of hydrogel. Based on that model, the kinetic parameters, activation energy (Ea) and preexponential factor (A), of the swelling process were determined to be Ea = 35 kJ/mol and lnA = 8.6. A possible mechanism of the investigated swelling process was discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
68.
The nonisothermal crystallization kinetics of a metallocene-made isotactic polypropylene (m-iPP) and its compounds with 0.1 wt % and 0.3 wt % of a sorbitol derivative [1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (DMDBS); an α nucleator] were investigated by differential scanning calorimetry at different cooling rates from the melt. The nucleation efficiency was proved by a significant increase in the crystallization temperatures (accompanied by a slight augmentation of the degree of crystallinity and a decrease in the crystal sizes). This increase in the crystallization temperatures led to higher amounts of fractional content in the γ polymorph, even though DMDBS was supposed to be a nucleator for the α form. The Avrami and Ozawa methods effectively described only the early stage of crystallization, whereas a combined Avrami–Ozawa method was valid for the whole crystallization process. The values of the exponent for this method decreased for nucleated samples in the later stage of crystallization, especially in the case of m-iPP with 0.3 wt % DMDBS added (m-iPP03). The activation energy of the process and the surface free energy were also estimated. The production of considerable proportions of the γ polymorph in m-iPP03 corresponded to higher values of the activation energy and lower values of the surface free energy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
69.
E. P. M. Leiva C. Vázquez M. I. Rojas M. M. Mariscal 《Journal of Applied Electrochemistry》2008,38(8):1065-1073
In this work, the structural and energetic properties of two typical catalytic surfaces, Na/Pt(111) and O/Pt(111), are studied
by means of quantum mechanical calculations and Monte Carlo Grand Canonical simulations. The simulations were performed with
electrostatic potentials at different truncation schemes. In order to elucidate the modification of catalyst surfaces produced
by the backspillover of ionic species onto Pt(111), the electrostatic field at the interface due to the electric double layer
was also analyzed. 相似文献
70.
Reda Karoum Antonio de Lucas-Consuegra Fernando Dorado Jose Luis Valverde Alain Billard Philippe Vernoux 《Journal of Applied Electrochemistry》2008,38(8):1083-1088
The electrochemical promotion of catalysis (EPOC) of propene combustion was investigated using Pt sputtered thin film on an
O2− conductor, 8 mol% Y2O3-stabilized-ZrO2 (YSZ). In order to separate the influence of the thermal migration of the O2− oxide ions from the electrolyte to the catalyst surface and the impact of an electrical polarization on the catalytic activity,
several light-off experiments (cool down and heat up procedures) were successively performed under different polarizations,
i.e. OCV, +2 and −2 V. These experiments have clearly shown that the presence of O2− (thermally or electrochemically induced) inhibits the catalytic activity of the platinum for the propene deep oxidation.
These results demonstrate the importance to define a normalized rate enhancement ratio, ρ
n
, from a reference value of the catalytic rate corresponding to a Pt surface state free of O2− ions. 相似文献