Showing papers on "Supporting electrolyte published in 1999"
TL;DR: In this article, it was shown that the heat of adsorption of hydrogen on Pt(111) at the electrochemical interface is essentially independent of either the pH of the electrolyte or the nature of the supporting anion.
Abstract: The variation of the adsorption pseudocapacitance with temperature is used to obtain the enthalpy, entropy, and free energies of adsorption of Hupd and OHad on Pt(111) as a function of pH and nature of the anion of the supporting electrolyte. It is shown that the heat (enthalpy) of adsorption of hydrogen on Pt(111) at the electrochemical interface is essentially independent of either the pH of the electrolyte or the nature of the supporting anion. The heat of adsorption has a linear decrease with ϑHupd, from ∼42 kJ/mol at ϑHupd = 0 ML to ∼24 kJ/mol at ϑHupd = 0.66 ML. The heat of adsorption of OHad is more sensitive to the nature of the anion in the supporting electrolyte. This is presumably due to coadsorption of the anion and OHad in electrolytes other than the simple alkali bases. From the isosteric heat of adsorption of OHad in alkaline solution (ca. ∼200 kJ/mol) and the enthalpy of formation of OH• we estimated the Pt(111)−OHad bond energy of 136 kJ/mol. This value is much smaller than the Pt−Oad bon...
297 citations
TL;DR: In this paper, a dependence of the PPy growing rate on the pore size and on the electrolyte nature and concentration has been observed, and the morphology of different template-synthesized nanostructures has been carefully analyzed by fieldemission scanning electron microscopy.
Abstract: Polypyrrole (PPy) with four different counterions was electrochemically synthesized in homemade polycarbonate particle track-etched membranes with different pore sizes. A dependence of the PPy growing rate on the pore size and on the electrolyte nature and concentration has been observed. The morphology of the different template-synthesized nanostructures has been carefully analyzed by field-emission scanning electron microscopy. In all cases, nanotubules were observed. However, their thickness depends on the pore diameter of the template membrane and on the nature of the supporting electrolyte. The electrical conductivity of PPy in such a structure is known to increase compared to the bulk conductivity, which is also shown here. In addition Raman spectroscopy showed that the relative conjugation length increases with decreasing pore size.
240 citations
TL;DR: In this paper, it was shown that in neutral aqueous solutions, the product of H 2 O 2 electrocatalytic reduction is OH − − − 2, and that the operational stability of Prussian Blue in H 2O 2 reduction was highly dependent on the buffer capacity of the supporting electrolyte.
231 citations
TL;DR: Using N-carbobenzyloxy-l-isoleucylaminooctadecane as a low molecular weight gelator for polar solvents, organogel electrolytes were prepared from supporting electrolyte and a polar solvent such as DMF, DMSO, and PC by physical gelation as mentioned in this paper.
Abstract: Using N-carbobenzyloxy-l-isoleucylaminooctadecane as a low molecular weight gelator for polar solvents, organogel electrolytes were prepared from supporting electrolyte and a polar solvent such as DMF, DMSO, and PC by physical gelation. The ionic conductivity of the prepared organogel electrolytes decreased very slightly with increasing concentration of gelator, while the gel strength drastically increased with increasing concentration. The organogel prepared from DMF exhibited relatively high ionic conductivity, interpreted due to the high mobility of carrier ions in the low-viscosity DMF. Arrhenius plots of ionic conductivities of organogel electrolytes indicate that the behavior of supporting electrolytes in the organogels is essentially similar to that in the isotropic solution, and the ionic mobility of supporting electrolytes is scarcely affected by the gelator molecules. The optimal concentration of supporting electrolytes in organogel electrolytes to achieve both high conductivity and high gel str...
166 citations
TL;DR: In this article, an analysis of the alternating current passage across a thin film containing mobile charge carriers of two types, which for the sake of specificity are referred to as "electrons" and "counterions", is presented.
152 citations
TL;DR: In this paper, the authors demonstrate the applicability of electrolytic procedures for the direct anodic (oxidative) degradation of toxic organic wastes, referred to as "electrochemical incineration" (ECI).
Abstract: This report summarizes results obtained as part of a larger effort to demonstrate the applicability of electrolytic procedures for the direct anodic (oxidative) degradation of toxic organic wastes. We refer to this process as “electrochemical incineration” (ECI) because the ultimate degradation products, e.g., carbon dioxide, are equivalent to those achieved by thermal incineration processes. In this work, the ECI of 4-chlorophenol is achieved in an aqueous medium using a platinum anode coated with a quaternary metal oxide film containing Ti, Ru, Sn, and Sb oxides. The electrode is stable and active when used with a solid Nafion membrane without the addition of soluble supporting electrolyte. Liquid chromatography (LC), including reverse phase and ion exchange chromatography, is coupled with electrospray mass spectrometry (ES-MS) and used, along with gas chromatography−mass spectrometry (GC-MS) and measurements of pH, chemical oxygen demand (COD), and total organic carbon (TOC), to study the reaction and ...
141 citations
TL;DR: In this paper, an electric double layer capacitor (EDLC) was prepared with an activated carbon powder electrode with poly(vinylidene fluoridehexafluoropropylene) (PVdF-HFP) based gel electrolyte.
Abstract: An electric double layer capacitor (EDLC) was prepared with an activated carbon powder electrode with poly(vinylidene fluoridehexafluoropropylene) (PVdF-HFP) based gel electrolyte. Ethylene carbonate (EC) and propylene carbonate (PC) were used as plasticizer and tetraethylammonium tetrafluoroborate (TEABF4) was used as the supporting electrolyte. An optimized gel electrolyte of PVdF-HFP/PC/EC/TEABF4 5 23/31/35/11 mass ratio exhibited high ionic conductivity of 5 3 10 23 S cm 21 , high electrode capacitance, and good mechanical strength. An electrode consisting of activated carbon (AC) with the gel electrolyte as the bind er (AC/PVdF-HFP based gel, 7/3 mass ratio) showed a higher specific capacitance and a lower ion diffusion resistance within the electrode than a carbon electrode, prepared with PVdF-HFP binder without plasticizer. This suggests that an electrode mixed with the gel electrolyte has a lower ion diffusion resistance inside the electrode. The highest specific capacitance of 123 F g 21 was achieved with an electrode containing AC with a specific surface area of 2500 m 2 g 21 . A coin-type EDLC cell with optimized components showed excellent cycleability exceeding 10 4 cycles with ca. 100% coulombic efficiency achieved when charging and discharging was repeated between 1.0 and 2.5 V at 1.66 mA cm 22 .
127 citations
TL;DR: In this paper, the effects of pH and supporting electrolyte concentration on the intrinsic viscosities of eight humic acids and one fulvic acid were evaluated and compared with two synthetic poly(acrylic acid) (PAA) samples.
113 citations
TL;DR: In this article, a review of recent progress in microelectrode voltammetry in solutions without or with low concentrations of supporting electrolyte is reviewed, where mathematical treatment of transport, experimental setup, steady state and non-steady state transport, migration coupled with homogeneous equilibrium, studies on the mechanism of the electrode processes, transport of ions in solutions of polyelectrolytes and colloids, and analytical applications are addressed.
112 citations
TL;DR: Electrochemical studies indicate that the adsorbed Co(II) complex on the surface of mercury is the active catalyst for the reduction of protons to dihydrogen.
Abstract: The macrocyclic cobalt hexaamines [Co(trans-diammac)]3+ and [Co(cis-diammac)]3+ (diammac = 6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine) are capable of reducing the overpotential for hydrogen evolution on a mercury cathode in aqueous solution. Protons are reduced in a catalytic process involving reoxidation of the CoII species to its parent CoIII complex. The cycle is robust at neutral pH with no decomposition of catalyst. The stability of the [Co(trans-diammac)]2+ and [Co(cis-diammac)]2+ complexes depends on the pH of the solution and the coordinating properties of the supporting electrolyte. Electrochemical studies indicate that the adsorbed CoII complex on the surface of mercury is the active catalyst for the reduction of protons to dihydrogen.
105 citations
TL;DR: In this paper, a rotating disc gold electrode is used for the determination of copper in μg−l−1 and sub-μg l−1 concentrations without removal of oxygen by the method of subtractive anodic stripping voltammetry (SASV).
TL;DR: In this paper, it was found that the relative contribution of anions and cations to the overall charge transport process depends upon several factors, such as the oxidation state of the polymer, the composition of the supporting electrolyte as well as on the film thickness.
Abstract: Electrochemical quartz crystal microbalance studies on poly(pyrrole) electrodes revealed a complex nature of the potential-dependent sorption of ionic substances. It is found that the relative contribution of anions and cations to the overall charge transport process depends upon several factors, such as the oxidation state of the polymer, the composition of the supporting electrolyte as well as on the film thickness. The phenomena observed are discussed in terms of morphological transformations arising as a result of interactions between the polymer and the mobile substances.
TL;DR: The viscosity at an arbitrarily selected shear rate of 1.16 s-1 and the yield stress of anatase dispersions are linearly correlated, and both show a maximum at the isoelectric point (IEP) at pristine conditions.
TL;DR: In this paper, the authors attempted continuous electrochemical decomposition of chloroform that is the main compound of trihalomethanes and some toxic chlorinated hydrocarbons in water using a metal-impregnated carbon fiber electrode (CFE).
Abstract: Trihalomethane and other chlorinated hydrocarbons are known to be toxic to human health. However, removal of these compounds from water is not easy. We attempted continuous electrochemical decomposition of chloroform that is the main compound of trihalomethanes and some toxic chlorinated hydrocarbons in water using a metal-impregnated carbon fiber electrode (CFE). At Ag- and Zn-impregnated CFE, concentration of chloroform in 0.5 M K2SO4 (the supporting electrolyte) solution was decreased from 0.25 m mol/L to below the limit of detection of our analysis system (1 ppm) at a flow rate of 1 mL/min. The main product of electrolysis was methane. This high efficiency, determined by the chemical yield, hardly changed at a flow rate of 20 mL/min at a Ag-impregnated CFE. At a flow rate of 1 mL/min, chloroform was degraded with a decomposition efficiency of almost 100% even in the solution without the supporting electrolyte, whereas at a higher flow rate, the efficiency for the decomposition of chloroform decreased ...
TL;DR: In this article, a planar positively-charged gold electrode surfaces were modified by consecutive adsorption of poly(styrene sulfonate), PSS, and protonated poly(allyl amine), PAH.
TL;DR: In this article, thin films of the redox polymer, [Ru(bpy)2PVP10] (ClO4)2, deposited on electrode surfaces are used for amperometric detection of oxalate.
TL;DR: The highly regioselective anodic monofluorination of 2-substituted 1,3-oxathiolan-5-ones was successfully carried out using a novel supporting electrolyte, Et(4)NF.4HF, while use of a conventional support electrolyte resulted in no formation or extremely low yields of the fluorinated products.
Abstract: The highly regioselective anodic monofluorination of 2-substituted 1,3-oxathiolan-5-ones was successfully carried out using a novel supporting electrolyte, Et(4)NF.4HF, while use of a conventional supporting electrolyte, Et(3)N.3HF, resulted in no formation or extremely low yields of the fluorinated products.
TL;DR: In this article, a simplified model for mass transfer processes in an electrochemical system can be characterized by an applied external magnetic field in diffusion controlled regime and the presence of a supporting electrolyte in excess in the bath is the major simplifying hypothesis for the electric current calculation.
TL;DR: In this article, in situ atomic force microscopy (AFM) was used to detect long needle-type crystals after long periods of redox cycling, which is consistent with the presence of a mixture of diffusion and surface processes in the initial cycles.
Abstract: The reduction of solid 7,7,8,8-tetracyanoquinodimethane (TCNQ) at an electrode-TCNQ-aqueous (electrolyte) is complex, irrespective of whether the solid on the electrode surface is attached by direct adherence or formed by electrochemical deposition. In order to understand the origin of reaction pathways that accompany the [TCNQ]0/− process, fast scan rate (0.1 V s−1) redox cycling and potential step experiments on TCNQ mechanically attached to a glassy carbon electrode placed in aqueous solution containing 0.1 M electrolyte (KCl, CsCl, or Et4NCl) have been monitored by the technique of in situ atomic force microscopy (AFM). The shapes of cycling voltammograms are consistent with the presence of a mixture of diffusion and surface processes in the initial cycles. AFM results show that, during the early stage of the redox cycling experiments, electrochemical reduction of TCNQ to sparingly soluble TCNQ− is accompanied by a redistribution process. This rearrangement results in the transformation of arrays of almost amorphous solid to a lower energy microcrystalline state which has a more thin film-type appearance. When CsCl is the electrolyte, long needle-type crystals are detected by the AFM method after long periods of redox cycling. The identity of the cation in the supporting electrolyte and the solubility of the reduced salt formed by reduction of TCNQ affect the nature of the voltammetry observed during early stages of redox cycling. When the redistribution process is completed and the stable crystalline phase is formed, the voltammetry of the [TCNQ]0/− couple is predominantly controlled by a nucleation-growth mechanism.
TL;DR: In this article, the steady-state voltammetric behavior for the oxidation of aqueous solutions containing the strong bases sodium and barium hydroxide was studied with gold microelectrodes in the absence and in the presence of different concentrations of supporting electrolyte.
Abstract: The steady-state voltammetric behavior for the oxidation of aqueous solutions containing the strong bases sodium and barium hydroxide was studied with gold microelectrodes in the absence and in the presence of different concentrations of supporting electrolyte. A well-defined oxidation wave attributed to the oxidation of hydroxide ions to oxygen was observed in all the solutions investigated, regardless of both the nature of the base and the supporting electrolyte employed. However, in solutions with excess electrolyte, the steady-state limiting current was found to depend on the actual concentration of the supporting electrolyte, as the diffusion coefficient of the electroactive species varies with both the ionic strength and viscosity of the medium. Since the hydroxide ion is a negatively charged species, solutions with low or without supporting electrolyte yielded currents enhanced by migration contributions. Theoretical equations for the dependence of steady-state limiting currents with ionic strength...
TL;DR: In this article, the electrochemical properties of solid films deposited on an electrode surface by simultaneous electrochemical reduction of C60 and palladium(II) acetate trimer in an acetonitrile/toluene mixture have been studied using cyclic voltammetry.
Abstract: The electrochemical properties of solid films deposited on an electrode surface by simultaneous electrochemical reduction of C60 and palladium(II) acetate trimer in an acetonitrile/toluene mixture have been studied using cyclic voltammetry. The electrochemical switching between the doped (conducting) and undoped (nonconducting) states involves both electron and ion transport within the film. The overall control of charge percolation through the C60/Pd electroactive material is governed by the transport of cations. The ion transport depends both on the nature of solvent and supporting electrolyte. The size of solvent molecule is the major factor determining the degree of solvent swelling of the layer. In the case of small solvent molecules, the C60/Pd film exhibits a reversible redox behavior. For larger molecule solvents, the voltammograms show a departure from reversibility. The reduction of the layer is accompanied by changes in its morphology allowing for the solvent swelling of the film also in the ca...
TL;DR: In this paper, the potential of titania particles in aqueous suspensions containing up to 1.2 mol dm −3 1-1 electrolyte is investigated. But the effect of the supporting electrolyte on the properties of relatively high solids fraction is not discussed.
TL;DR: In this paper, the advantages and disadvantages of electrochemistry with little or no added supporting electrolyte are reviewed, and a framework of procedures is derived which may be followed to obtain a solution to many transient voltammetric problems at a macroelectrode.
Abstract: The advantages and disadvantages of electrochemistry with little or no added supporting electrolyte are reviewed. Analysis of such systems is complicated by the increased importance of the migrational component of transport. Some computations and analyses can be simplified by invoking the principle that for any electrochemical experiment where the diffusivities of all the solute species do not differ significantly from a common value, the total solute concentration remains uniform and constant. This principle, which applies to both transient and steady-state regimes, holds independently of the cell and electrode geometries and is not compromised by migration and/or convection. The only constraint, additional to the assumption of uniform diffusivities, is the obvious one: that the electron-transfer reaction, and any homogeneous reactions that may participate, do not themselves perturb the number of solute particles (molecules and ions) present. Some consequences of the principle are explored, especially relating to three-ion systems. Using the principle, a framework of procedures is derived which may be followed to obtain a solution to many transient voltammetric problems at a macroelectrode when supporting electrolyte is absent.
Journal Article•
TL;DR: In this article, the electrochem behavior of some model org.d. on boron-doped synthetic diamond thin film electrodes, obtained by HF-CVD on p-Si substrate was investigated.
Abstract: The electrochem. behavior of some model org. compds. on boron-doped synthetic diamond thin film electrodes, obtained by HF-CVD on p-Si substrate was investigated. Only reactions involving simple electron transfer like hydroquinone/benzoquinone are active in the potential region of the supporting electrolyte stability, although this system is irreversible on diamond electrodes. For oxidn. reactions with more complex mechanism, diamond electrodes show no electrocatalytic activity in the potential region of the supporting electrolyte stability. These complex oxidn. reactions can take place on diamond electrodes in the potential region of the supporting electrolyte decompn. The reactivity of some alcs. and carboxylic acids is studied by cyclic voltammetry. Isopropanol in 1 M H2SO4 is oxidized on diamond anode at a const. c.d. and the intermediates formed are analyzed by HPLC. Finally, a simplified mechanism for the oxidn. of orgs. by electrogenerated OH radicals on diamond is proposed. [on SciFinder (R)]
01 Jan 1999
TL;DR: In this paper, the dissociation constants of acetic, oxalic, citric, and ethylenediaminetetraacetic acids were determined using a hydrogen ion glass electrode at 25 °C in solutions of ionic strengths ranging from 0.3 to 5.0 m NaCl.
Abstract: Dissociation constants (pK a ) of acetic, oxalic, citric, and ethylenediaminetetraacetic acids have been determined potentiometrically using a hydrogen ion glass electrode at 25 °C in solutions of ionic strengths ranging from 0.3 to 5.0 m NaCl. The observed ionic strength dependencies of the pK a values have been described successfully over the entire ionic strength range using both the Specific Ion Interaction Theory and the Pitzer model. The variation of the pK a values at high ionic strengths with the type and concentration of supporting electrolyte is discussed and compared to literature data.
TL;DR: In this paper, the authors investigated the electrocatalytic behavior of Ti/RuO2 and Ti/IrO2 electrodes as function of the supporting electrolyte and solvent and found that a decrease was observed in the electrochemically active area of the electrode as the cation size increases.
TL;DR: In this article, the electrochemical reduction of dichlorodifluoromethane (CFC-12) at Ag, Cu, Au, Pt and Ni electrodes in acetonitrile and 0.1 M (C 4 H 9 ) 4 NBr as supporting electrolyte has been studied.
TL;DR: The effect of supporting electrolyte on the enzyme activity revealed that SDS was the best in the immobilization procedure, and in terms of repeated use, the copolymer matrices were superior to polypyrrole.
Abstract: Immobilization of invertase in thiophene-capped poly(methylmethacrylate)/polypyrrole matrices was achieved by constant potential electrolysis using different supporting electrolytes. Optimum reaction conditions such as substrate concentration, temperature, and pH for the enzyme electrodes were determined. The temperature and pH were found to be 60°C and 4.8, respectively. The effect of supporting electrolyte on the enzyme activity revealed that SDS was the best in the immobilization procedure. Michaelis-Menten constant and the maximum reaction rate in PMMA/PPy matrices were of the order of that of pristine polypyrrole. However, in terms of repeated use, the copolymer matrices were superior to polypyrrole.
TL;DR: In this article, a regioselective electrochemical fluorination of 2-pyrimidyl sulfides having an electron-withdrawing group (EWG) at the position α to the sulfur atom was successfully carried out using Et4NF·nHF (n = 3, 4) or Et3N·3HF as a supporting electrolyte and a fluoride ion source in 1,2-dimethoxyethane (DME) in an undivided cell.
Abstract: Highly regioselective electrochemical fluorination of 2-pyrimidyl sulfides having an electron-withdrawing group (EWG) at the position α to the sulfur atom was successfully carried out using Et4NF·nHF (n = 3, 4) or Et3N·3HF as a supporting electrolyte and a fluoride ion source in 1,2-dimethoxyethane (DME) in an undivided cell. 2-Methylthiopyrimidine devoid of an EWG was also selectively fluorinated in DME to provide 2-(fluoromethylthio)pyrimidine in a moderate yield as 63%, while corresponding 2-methylthiopyridine was less selectively fluorinated in lower yield along with α,α-difluorinated product. In contrast, the corresponding 2-quinazolinonyl sulfides underwent similarly α-fluorination along with unexpected ipso-fluorination through anodic desulfurization.
TL;DR: In this paper, a new copper-piroxicam complex was synthesized by electrochemical dissolution of sacrificial metallic anodes in an acetonitrile solution of the ligand.