Showing papers on "Supporting electrolyte published in 2000"

Electrochemical and in Situ Ellipsometric Investigation of the Permeability and Stability of Layered Polyelectrolyte Films

Abstract: Utilization of layered polyelectrolyte films as sensor or ion-separation materials will depend critically on their stability and ion permeability in aqueous solution. We report electrochemical and in situ ellipsometric studies on the permeability and stability of poly(allylamine hydrochloride)/poly(styrenesulfonate) (PAH/PSS) and PAH/poly(acrylic acid) (PAA) films. The permeability of these layered polyelectrolyte films to Fe(CN)63- and Ru(NH3)63+ depends on the solution pH, the number of bilayers in the film, whether supporting electrolyte is present during film deposition, and the nature of constituent polycations and polyanions. Cyclic voltammetry and impedance spectroscopy show that film permeability is similar in pH 3.2- and pH 6.3-buffered solutions but increases dramatically in alkaline solutions. In situ ellipsometry helps to explain these results. Upon immersion in pH 3.2- and pH 6.3-buffered solutions, the thickness of PAH/PSS films increases by 40%, but swelling is constant over time. At pH 10,...

Oxidation of carboxylic acids at boron-doped diamond electrodes for wastewater treatment

Abstract: Thin boron-doped diamond films have been prepared by HF CVD (hot filament chemical vapour deposition technique) on conductive p-Si substrate (Si/Diamond). The morphology of these Si/diamond electrodes has been investigated by SEM and Raman spectroscopy. The electrochemical behaviour of the Si/diamond electrodes in 1 M H2SO4 and in 1 M H2SO4 + carboxylic acids has been investigated by cyclic voltammetry. Finally, the electrochemical oxidation of some simple carboxylic acids (acetic, formic, oxalic) has been investigated by bulk electrolysis. These acids can be oxidized at Si/diamond anodes to CO2, in the potential region of water and/or the supporting electrolyte decomposition, with high current efficiency.

Electrochemical oxidation of dyeing baths bearing disperse dyes

Abstract: This paper presents the results of the electro-oxidation of pollutants in synthetic textile wastewater containing partially soluble disperse dyes. The experiments were performed in an electrochemical undivided cell reactor using seven different anode materials and 0.1 M NaCl as the supporting electrolyte. With the Ti/Pt−Ir anode, which showed the best performance among all the tested materials, additional experiments were also carried out using 0.05 M Na2SO4 as the supporting electrolyte. Experimental results obtained in the electrochemical reactor, supported by the data obtained during cyclic voltammetry studies, showed that under the conditions of the present research the removal of pollutants was mediated by active chlorine generated by electro-oxidation of chloride ions or by other mediators generated in situ and not by a direct discharge of pollutants at the anode. Under the conditions of free pH evolution 39% removal of chemical oxygen demand was obtained after 40 min of electrolysis. The apparent p...

Achievement of Near-Reversible Behavior for the [Fe(CN)6]3-/4- Redox Couple Using Cyclic Voltammetry at Glassy Carbon, Gold, and Platinum Macrodisk Electrodes in the Absence of Added Supporting Electrolyte

Abstract: Voltammetric studies in the absence of added supporting electrolyte are presently dominated by the use of near-steady-state microelectrode techniques and millimolar or lower depolarizer concentrations. However, with this methodology, large departures from conventional migration−diffusion theory have been reported for the [Fe(CN)6]3-/4- process at both carbon fiber and platinum microdisk electrodes. In contrast, data obtained in the present study reveal that use of the transient cyclic voltammetric technique at glassy carbon, gold, or platinum macrodisk electrodes and K4[Fe(CN)6] or K3[Fe(CN)6] concentrations of 50 mM or greater provides an approximately reversible response in the absence of added electrolyte. It is suggested that the use of very high [Fe(CN)6]3- and [Fe(CN)6]4- concentrations overcomes problems associated with a diffuse double layer and that large electrode surface areas and faster potential sweep rates minimize electrode blockage and passivating phenomena that can plague voltammetric stu...

Immobilization of invertase in functionalized copolymer matrices

Abstract: In this study, immobilization of invertase on functionalized polymer electrodes constructed with pyrrole-capped polyazotetrahydrofuran and polytetrahydrofuran-block-polystyrene copolymer matrices was performed. Immobilization in these enzyme electrodes was carried out by the entrapment of the enzyme in conducting polymer matrices during electrochemical polymerization of pyrrole. Sodium dodecyl sulphate was used as the supporting electrolyte in the preparation of enzyme electrodes. The effects of temperature and pH on the activity of the enzyme electrodes were examined, and re-use number studies were performed. The changes in the maximum reaction rate and the variations of the Michaelis–Menten constant were investigated.

Battery electrolytic solution with fluoride-ion-dissociating salt and battery using the same

Abstract: The present invention relates to an electrolytic solution excellent in stability, and also relates to a battery excellent in battery performance and having an outer structure having light weight. The electrolytic solution contains a supporting electrolyte and a gas formation inhibitor in the solvent. The gas formation inhibitor contains a decomposition product of the supporting electrolyte with formation of a gas in the solvent. It functions as controlling to solution equilibrium in the electrolytic solution participating in decomposition reaction of the supporting electrolyte. A battery is obtained by filling the electrolytic solution between a positive electrode and a negative electrode.

A Study of Surface Properties of Red Mud by Potentiometric Method

Abstract: A bauxite waste of alumina manifacture, ie, red mud (RM), is an oxide-like adsorbent capable of removing radiocesium and strontium The adsorption behavior of these radionuclides is dominated by the surface charge of the adsorbent and the number of available adsorption sites In this study, the surface charge densities (sigma), microscopic acidity constants (pK(s)), and site distributions of the RM in 10(-3)-1 M concentrations of NaCl, CsCl, and SrCl(2) solutions were evaluated from potentiometric titration data The reciprocal slopes of the pH-sigma curves are higher than those predicted by double-layer theory This suggests that surface charge and the counter charge are located in a region inside the surface because the porous and/or gel surface layer is permeable to these ions Ionic strength dependency of sigma in CsCl solutions is similar to those found for other oxides In SrCl(2) and NaCl solutions, at any pH the surface charge decreases as the electrolyte concentration increases This behavior of the RM may be attributed to the existence of differently charged oxide surface sites of variable affinity for electrolyte ions Uptake of protons on these sites could be interpreted in terms of H(+) adsorption and well described by the Freundlich equation The empirical Freundlich parameters were used to characterize a site distribution function which provides information about the affinity ratio of the adsorption sites to H(+) and supporting electrolyte cations Copyright 2000 Academic Press

Electrochemical Studies of C60/Pd Films Formed by the Reduction of C60 in the Presence of Palladium(II) Acetate Trimer. Effects of Varying C60/Pd(II) Ratios in the Precursor Solutions

Abstract: Cyclic voltammetric studies of the electrochemical formation and redox properties of C60/Pd films are reported. Films used in this work are generated under multicyclic scans in an acetonitrile/toluene (1:4, v/v) mixture containing fullerene C60 and palladium(II) acetate trimer as the film precursors and tetra(n-butyl)ammonium perchlorate as supporting electrolyte. The structure and electrochemical properties of the deposited layers depend on the relative concentrations of the precursors (C60 and {Pd(OAc)2}3) present in the growth solution. In the presence of excess palladium(II) acetate trimer, palladium, as well as the redox active film, is deposited, as shown by electrochemical studies of the behavior of the modified electrodes toward hydrogen evolution and palladium oxidation in aqueous acidic solution. At very negative potentials, all of the films decompose which is presumed to be due to the repulsive interaction between negatively charged C60 centers and mechanical strain induced by the incorporation...

Effect of Electrode Density of States on the Heterogeneous Electron-Transfer Dynamics of Osmium-Containing Monolayers

Abstract: Dense monolayers of [Os(OMe-bpy)2(p3p)Cl]1+, where OMe-bpy is 4,4‘-dimethoxy-2,2‘-bipyridyl and p3p is 4,4‘-trimethylenedipyridine, have been formed by spontaneous adsorption onto clean platinum, mercury, gold, silver, carbon, and copper microelectrodes These systems have been used to probe the influence of the electrode density of states on the rate of electron transfer across the electrode/monolayer interface Monolayers on each material exhibit well-defined voltammetry for the Os2+/3+ redox reaction where the supporting electrolyte is aqueous 10 M NaClO4 The high scan rate (>2000 V s-1) voltammetric response has been modeled using a nonadiabatic electron-transfer model The standard heterogeneous electron-transfer rate constant, k°, depends on the identity of the electrode material, eg, k° is 6 × 104 and 4 × 103 s-1 for platinum and carbon electrodes, respectively Chronoamperometry, conducted on a microsecond time scale, has been used to probe the potential dependence of the heterogeneous electro

Flat non-aqueous electrolyte secondary cell

Abstract: In a flat non-aqueous electrolyte secondary cell comprising an electricity-generating element including at least a cathode, a separator and an anode and a non-aqueous electrolyte in the inside of a cathode case, a plurality of electrode units each consisting of the cathode and the anode opposite to each another via the separator are laminated to form an electrode group, or an electrode unit in a sheet form consisting of the cathode and the anode opposite to each another via the separator is wound to form an electrode group, or a sheet-shape cathode is wrapped with the separator except for a part contacting at inner face of cathode case and a sheet-shaped anode is set on the sheet-shaped cathode in a right angled position each other and then these cathode and anode are bent alternately to form an electrode group, and the total sum of the areas of the opposing cathode and anode in this electrode group is larger than the area of the opening of an insulating gasket in a sealed portion in the cathode case or than the area of an opening in a sealed plate in a sealed portion in the cathode case, whereby the discharge capacity upon heavy-loading discharge is significantly increased as compared with the conventional cells. Accordingly, while the size of the cell is small, the discharge capacity is increased as described above, and thus it is possible to provide a highly utilizable flat non-aqueous electrolyte secondary cell. Further, in said flat non-aqueous electrolyte secondary cell, problems which may be caused by the increased discharge capacity in the cell can be solved by improving the solvent and supporting electrolyte for the electrolyte or by various improvements in the cathode and anode cases.

Studies of Double-Layer Effects at Single-Crystal Gold Electrodes. 1. The Reduction Kinetics of Hexaamminecobalt(III) Ion in Aqueous Solutions

Abstract: The effect of the double-layer on the reduction of [Co(NH3)6]3+ cation has been studied at four different single-crystal gold substrates, namely, Au(111), Au(100), Au(110), and Au(210), and at various concentrations of perchloric acid. The values of the experimental transfer coefficient (αex) are much larger than 1.0 at all gold surfaces and decrease with increasing concentration of the supporting electrolyte. The value of αex also depends on the crystallographic orientation of the gold substrate and increases in the following order: Au(111) < Au(100) < Au(110) < Au(210), consistent with a decreasing reduction rate from Au(111) to Au(210) at constant electrode potential. The experimental transfer coefficients are rationalized on the basis of the classical theory of the double-layer with consideration of reactants and products in estimation of the diffuse-layer potential. The charge on the reactant transported through the double-layer is 2+. Corrected Tafel plots yield an apparent transfer coefficient αa ...

Voltammetric and amperometric detection without added electrolyte.

Abstract: Eliminating or using very little supporting electrolyte provides opportunities for new types of voltammetry and amperometry experiments

Electron Transfer Kinetics of Tris(1,10-phenanthroline)ruthenium(II) Electrooxidation in Aprotic Solvents

Abstract: Double layer and solvent effects on the kinetics of the one-electron oxidation of Ru(phen)32+ (where phen = 1,10-phenanthroline) at platinum and gold ultramicroelectrodes were studied by ac-voltammetry. The standard rate constant of Ru(phen)32+ electrooxidation is independent of both electrode material and concentration of supporting electrolyte, indicating the absence of double-layer effects on the kinetics of electron transfer. The small variation of the formal redox potential of the Ru(phen)32+/3+ system with change of the supporting electrolyte concentration demonstrates the absence of a significant influence of ion pairing on the reaction rate. Therefore, the electrode process of Ru(phen)32+ oxidation is found to be ideally suitable for the study of solvent effects on electron transfer kinetics. The solvent dependence of the electron transfer rate constant was interpreted within the context of contemporary theory. The charge transfer process was found to be perfectly adiabatic. Since the crossing rat...

Nitric oxide solutions : standardisation by chronoamperometry using a platinum disc microelectrode

Abstract: Studies on the anodic oxidation of nitric oxide (NO) at platinum microdiscs have been performed. Results obtained with platinum disc microelectrodes of various radius values showed that the process is mass transport controlled. At 0.9 V (versus Ag/AgCl), current–time data were analysed according to an analytical expression that describes the chronoamperometric transient at a disc microelectrode and allows the determination of the diffusion coefficient of the electroactive species as well as its concentration. From chronoamperometric curves obtained by using a 25 μm radius platinum microelectrode, the concentration of NO in saturated solutions prepared at 25 °C in phosphate buffer (pH 7.4) was found to be (2.1 ± 0.3) × 10−3 mol dm−3. In the same supporting electrolyte, the data led to the calculation of the diffusion coefficient of NO, the value being 1.2 × 10−5 cm2 s−1.

Determination of carbendazim in soil samples by anodic stripping voltammetry using a carbon fiber ultramicroelectrode

Abstract: A method for the determination of carbendazim (MBC) by anodic stripping voltammetry using a carbon fiber ultramicroelectrode was developed. The ultramicroelectrode was made in our laboratory and its electrochemical behavior was characterized by measuring the electrochemical response with a solution of potassium ferricyanide. The optimum parameters used for the determination of MBC are the following: 0.05 M phosphate buffer at pH 2.0 as supporting electrolyte; a scan rate of v = 10.00 V s–1 and an accumulation potential of Eac = 0.00 V. The MBC was determined in a soil sample with the method proposed and the results found were comparable to those obtained by HPLC.

Electrochemical Behavior and Determination of Ketoconazole from Pharmaceutical Preparations

Abstract: The oxidation of ketoconazole (KC) was investigated by rotating disk electrode voltammetry, cyclic voltammetry, and controlled potential coulometry in chloroform at platinum (Pt), gold (Au), and glassy carbon (GC) electrodes using tetrabutylammonium perchlorate as supporting electrolyte. Based on the electrochemical results obtained, the following possible mechanism was proposed to explain the electrochemical oxidation of KC KC ⇌-e KC·+ -e P P′ A differential pulse voltammetric method at a Pt electrode was developed for the determination of KC from pharmaceutical preparations in the concentration of 3.0×10–6–1.0×10–4 M. The procedure was applied to the determination of KC in its tablets and creams as well as its recovery from blood serum and urine samples.