| 1. |
- Larsson, Henrik, et al.
(författare)
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Electron transport in quaternized poly(4-vinylpyridine) films containing pentacyanoferrate(II/III) on electrodes. The influence of the binding type of the electroactive complex
- 1992
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 336:1-2, s. 263-279
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Tidskriftsartikel (refereegranskat)abstract
- This study is an attempt to investigate how charge transport in thin redox polymer films spin-coated onto glassy carbon electrode surfaces is affected by the way in which the electroactive group is bound to the polymeric matrix. Two different redox polymers based on methylated and cross-linked poly(4-vinylpyridine) and pentacyanoferrate(II/III) have been synthesized. In the first case, an anionic complex formed by coordinating pyridine to pentacyanoferrate(II) was electrostatically bound to the methylated pyridine groups in the polymer matrix. In the other case, pentacyanoferroate(II) was coordinated directly to unmethylated pyridine groups in the partly methylated polymer film. The film thicknesses were estimated with ellipsometric measurements. Their electrochemical characteristics were investigated using cyclic voltammetry, chronocoulometry and impedance spectroscopy. The apparent charge-transport diffusion coefficient D(app) was almost two orders of magnitude greater in the ion-exchange polymer than in the redox polymer with coordinatively bound electroactive groups. The temperature dependence of D(app) was evaluated using Arrhenius plots.
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| 2. |
- Fontes, Eduardo, et al.
(författare)
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Mathematical modelling of the MCFC cathode : On the linear polarisation of the NiO cathode
- 1997
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Ingår i: Journal of Electroanalytical Chemistry. - 0022-0728 .- 1873-2569. ; 432:1-2, s. 121-128
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Tidskriftsartikel (refereegranskat)abstract
- Experimental polarisation curves for the porous lithiated NiO cathode used in molten carbonate fuel cells very often exhibit a linear shape over a wide potential range. It is shown by means of mathematical modelling that this linear behaviour can be explained by the interplay of intrinsic electrode kinetics, diffusion of electroactive species through an electrolyte film and the effective ohmic resistance of the pore electrolyte, providing that the cathodic transfer coefficient has a value of about 1.5. In contrast, with the generally assumed value of 0.5 of this transfer coefficient and with reasonable values of the effective electrolyte conductivity, predicted polarisation curves will always bend downwards over the overvoltage region of interest. The evolution of the polarisation curves with increasing electrolyte fill can be simulated by a model according to which the electroactive surface area becomes gradually blocked with the increasing amount of electrolyte.
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| 3. |
- Larsson, Henrik, et al.
(författare)
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Charge propagation in [Os(bpy)2(PVP)xCl]Cl polymers. An example of mean field behavior in a system with constrained diffusion of redox sites?
- 1995
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 0022-0728 .- 1873-2569. ; 381:1-2, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- Chronocoulometry and impedance spectroscopy were used to study the dynamics of charge transport in a series of methylated [Os(bpy)(2)(PVP)(x)Cl]Cl polymers (PVP = poly(4-vinylpyridine); bpy = 2,2'-bipyridine; 5 less than or equal to x less than or equal to 40) which were deposited as thin firms on glassy carbon electrodes. Apparent charge propagation diffusion coefficients D-app were of the order of 10(-8) cm(2) s(-1) and were approximately linearly dependent on the total concentration of redox sites but independent of the ratio of oxidized to reduced centres present in a particular coating. Attempts were made to explain these observations in terms of a recent theory of charge transport appropriate for systems in which the redox sites are permanently attached to the polymer chains. It was found that the concentration dependence and magnitude of D-app could be explained satisfactorily by a mean field model of charge propagation.
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| 4. |
- Sharp, Michael, et al.
(författare)
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Studies of the temperature dependence of charge propagation rates in quaternized poly(4-vinylpyridine) polymers containing electrostatically bound and coordinated redox sites
- 1995
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 0022-0728 .- 1873-2569. ; 386:1-2, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- The activation parameters associated with charge propagation in a series of quaternized poly(4-vinylpyridine) polymers, which contained both electrostatically hound and coordinated redox sites and which were deposited as thin films on electrode surfaces, were derived from the temperature dependence of apparent charge transport diffusion coefficients. The values of the activation energies and entropies obtained are discussed in terms of models of charge transport that are appropriate for redox polymers in which physical displacements of the redox sites are either free or constrained.
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| 5. |
- Yang, Zhongping, et al.
(författare)
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Electrochemical characterisation of mixed monolayer assemblies of thiol analogues of cholesterol and fatty acids on gold
- 1997
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier Science B.V., Amsterdam.. - 0022-0728 .- 1873-2569. ; 430:1-2, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- A self-assembled monolayer (SAM) on gold prepared from a binary mixture of a thiol analogue of cholesterol (thiocholesterol, TC) and a functionalised alkanethiol (11-mercaptoundecanoic acid, MUA) has been investigated by voltammetry. The voltammetric results are in agreement with previously reported spectroscopic data and show that the geometric arrangement and composition of the molecules in the mixed monolayer controls the heterogeneous electron transfer process of Fe(CN)(6)(3-) across the assembly. The quantitative description of the influence of TC on the electron transfer rate constant is given through Tafel plots. At the pure MUA SAM electrode, the electron transfer is governed by penetration through the monolayer. The introduction of TC into the SAMs creates defects giving rise to diffusion controlled electron transfer in addition to penetration. By raising the TC content the electron transfer rate constant increases due to diffusion, This behaviour can be explained by a model in which the assembly goes from a penetrative but defect-free film barrier (pure MUA SAM) via a structure with defects in the mixed composition regime to a defect-rich structure consisting of an array of ultramicroelectrodes (pure TC SAM). (C) 1997 Elsevier Science S.A.
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| 6. |
- Larsson, Henrik
(författare)
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Ellipsometric determinations of the thicknesses of dry and electrolyte-immersed poly(4-vinylpyridine) films containing coordinated light-absorbing [Os(bpy)2pvpCl]2+/+ redox groups
- 1994
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 1572-6657 .- 1873-2569. ; 365:1-2, s. 229-237
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Tidskriftsartikel (refereegranskat)abstract
- Ellipsometry has been used to measure the dimensions of quaternized poly(4-vinylpyridine) films containing [Os(bpy)2pvpCl]2+/+ redox groups on glassy carbon electrodes. Film thicknesses and complex refractive indices were deduced using molar absorptivities obtained from photometry or a combination of photometry and cyclic voltammetry. The precision in the film thicknesses was estimated using data obtained from thick and thin films with the same polymer + redox group compositions and from data recorded at 60-degrees and 70-degrees angles of incidence of 633 nm laser light. The effects of errors in the experimentally determined molar absorptivity of the redox groups on film thickness were also assessed. The results of this study suggest that reliable thicknesses can be obtained for both dry and electrolyte-swollen films, and that the presence of light-absorbing redox groups within coatings such as these presents no real obstacle for ellipsometric determinations.
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| 7. |
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| 8. |
- MATTSSON, G, et al.
(författare)
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CATHODIC STRIPPING VOLTAMMETRY OF CU2SE AT MERCURY-ELECTRODES
- 1994
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Ingår i: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : ELSEVIER SCIENCE SA LAUSANNE. - 0022-0728. ; 379:1-2, s. 49-61
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemistry of the codeposition of Se(IV) and Cu2+ at a hanging-mercury-drop electrode has been studied in detail in 0.1 M HClO4 or HCl solutions. Films consisting of Cu2Se are formed and the cathodic stripping of these films results in a single
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