Double-layer Capacitance Measurements Research Articles

Investigation of the Hg/HCl aq. system by capillary electrometers based on maximum bubble pressure method and by classical capillary electrometer Comparison of interfacial tension and double-layer capacity data

The Hg/HCl aq. system was studied using capillary electrometers based on the maximum bubble pressure principle (that employed either an inverted capillary or a vertical capillary) and by the classical capillary electrometer. All three versions of the capillary electrometer yielded interfacial tension data of high precision, except that the modified capillary electrometer with a vertical capillary and the classical electrometer gave data of slightly lower quality over a narrow range of extreme negative polarization for 0.01 M HCl solution. Based on the electrocapillary and double-layer capacity measurements carried out on identical HCl solutions (0.01 M–1 M), it is shown that there exists a very good correspondence between the measured and derived quantities as compared to the agreement previously observed by Bockris and co-workers (who employed a classical capillary electrometer in their interfacial tension measurements).

344 - Some relations between the electrosorption behaviour and cation charge transfer at homologous lecithin model membranes - a.c. and d.c. polarographic measurements. Preliminary communication

The electrosorption properties of 1,2-di-palmitoyl-lecithin, 1,2-di-lauroyl-lecithin and 1,2-di-stearyl-lecithin were studied using double-layer capacitance measurements in ethanol + water mixtures (in the volume ratios 96/4 and 90/10) in various supporting electrolytes [LiClO 4, (C 4H 9) 4NClO 4, NH 4NO 3]. In ethanolic lithium perchlorate solutions two potential ranges of maximum adsorption were found which correspond to various structures of the adsorption layer. On the positively charged interface the double-layer capacitance is suppressed up to 5 μF/cm 2. A condensed adsorption layer is formed on the negatively charged interface, which is supported by very deep double-layer capacitance values C < I μF/cm 2 between U = −1.2 V and U = −2 V. For all other indifferent cations the adsorption on the positively charged interface is predominant. The two adsorption ranges of maximum adsorption seems to be caused by different molecule orientation. The barrier properties of phospholipids were studied by d.c. polarography. The inhibition phenomena were only found in the supporting electrolytes containing LiClO 4. Otherwise in the 0.2 M NH 4NO 3 and 0.1 M (C 4H 9) 4NClO 4 this effect could not be observed. The retardation of the electrode process of Tl +, Cd 2+ and Zn 2+ takes place in the region between U = −1.2 V and U = −2.0 V where a condensed adsorption layer is formed (in 0.2 M LiClO 4).

Double layer capacitance measurements with digital synchronous detection at a dropping mercury electrode

Double layer capacitance measurements with digital synchronous detection at a dropping mercury electrode

Application of pattern recognition techniques to qualitative electrochemical analysis Part II. On-line measurements of double-layer capacity by the superimposition method and adaptive compensation of charging current by the capacitance multiplier

Application of pattern recognition techniques to qualitative electrochemical analysis Part II. On-line measurements of double-layer capacity by the superimposition method and adaptive compensation of charging current by the capacitance multiplier

Some relations between the electrosorption behaviour and cation charge transfer at homologous lecithin model membranes— a.c. and d.c. polarographic measurements. Preliminary communication

Abstract The electrosorption properties of 1,2-di-palmitoyl-lecithin, 1,2-di-lauroyl-lecithin and 1,2-di-stearyl-lecithin were studied using double-layer capacitance measurements in ethanol + water mixtures (in the volume ratios 96/4 and 90/10) in various supporting electrolytes [LiClO4, (C4H9)4NClO4, NH4NO3]. In ethanolic lithium perchlorate solutions two potential ranges of maximum adsorption were found which correspond to various structures of the adsorption layer. On the positively charged interface the double-layer capacitance is suppressed up to 5 μF/cm2. A condensed adsorption layer is formed on the negatively charged interface, which is supported by very deep double-layer capacitance values C For all other indifferent cations the adsorption on the positively charged interface is predominant. The two adsorption ranges of maximum adsorption seems to be caused by different molecule orientation. The barrier properties of phospholipids were studied by d.c. polarography. The inhibition phenomena were only found in the supporting electrolytes containing LiClO4. Otherwise in the 0.2 M NH4NO3 and 0.1 M (C4H9)4NClO4 this effect could not be observed. The retardation of the electrode process of Tl+, Cd2+ and Zn2+ takes place in the region between U = −1.2 V and U = −2.0 V where a condensed adsorption layer is formed (in 0.2 M LiClO4).

Application of pattern recognition techniques to qualitative electrochemical analysis: Part II. On-line measurements of double-layer capacity by the superimposition method and adaptive compensation of charging current by the capacitance multiplier

A random voltage signal with a larger amplitude for the faradaic electrolysis, on which a high-frequency small sinusoidal ac voltage signal is superimposed, has been used as a input signal. The response current of the ac voltage signal consists of the charging current. Gain values and phase values of the electrochemical double layer, which are obtained by comparison of input and output of the high-frequency signal, are located against the sample value of the electrode potential ( E) at each moment using a microcomputer, and the images of both E−C dl (gain) and E− (phase) patterns come out gradually in the memory of the microcomputer, where C dl is the double-layer capacity and θ is the phase difference. The gain values are used for the control of the capacitance multiplier, which becomes an accurate and real-time simulator of the practical electrochemical double layer at the different electrode potential. An adaptive and real-time compensation of the charging current has been achieved merely by the analog subtraction of the current flowing through the capacitance multiplier (only the low-frequency potentiostatic signal is applied to its input terminal) instantaneously from the low-frequency response current.

ChemInform Abstract: SEMICONDUCTING PROPERTIES OF ANODICALLY FORMED LAYER ON ANTIMONY

AbstractAus Photopolarisations‐ und ‐leitfähigkeits‐ sowie Doppelschichtkapazitätsmessungen am System Sb/Oxidschicht/Elektrolyt folgt, daß die anodischen Oxidschichten auf Sb Halbleiter vom n‐Typ sind mit einer verbotenen Zone Eg = 3 eV und der Donatordichte ND ≈︁ 1017 cm‐3.

Adsorption of ethylene glycol and its higher homologues at the mercury/aqueous solution interface

Adsorption of ethylene glycol, propan-1,2-diol and butan-1,4-diol at the Hg/0.10 mol kg–1 KCl (aq.) solution interface evaluated through equilibrium double layer capacity measurements indicated congruency of adsorption isotherms with respect to both electrode charge (σM) and potential (E); applicability of Langmuir's adsorption isotherm; quadratic dependence of Δtext-decoration:overlineG° on E and single stable orientation with the hydrocarbon chain facing the electrode and functional group in solution throughout the coverage region for all these compounds. Surface excess, standard free energy of adsorption and the anodic shift of Epzc are in the order: ethylene glycol < propan-1,2-diol < butan-1,4-diol. The shift of charge corresponding to maximum adsorption towards less negative charges in passing from ethylene glycol to butan-1,4-diol has been explained with the help of an equation given by Damaskin and Frumkin.

Semiconducting properties of anodically formed layer on antimony

Results of photopolarization, photoconductivity and double layer capacity measurements for the sytem Sb/oxide layer/electrolyte have been given. On the basis of the above measurements it has been concluded that anolic layers on antimony as examined are semiconductors of n-type, band gap E g=3 eV and donor density N D≈10 17 cm −3. The dependence of photovoltage on barrier layer thickness of the Schottky type calculated on the basis of experimental results, also supports the above conclusion, that is, the minimum thickness in which significant photo-effect still appears is of the order of magnitude 10 −5 cm, which seems plausible with respect to the expected of light absorption coefficient.

Adsorption of 1,2-Propanediol and Methyl Cellosolve at Mercury— 0.10 m KCl aq Interface at 25 °C

Abstract Adsorption of 1,2-propanediol and methyl cellosolve (isomeric compounds) at Hg–0.10 m KCl (aq) solution interface evaluated through equilibrium double layer capacity measurements indicated congruency of adsorption isotherms with respect to both potential (E) and charge density (σM); applicability of Langmuir’s adsorption isotherm; quadratic dependence of Δ\barG° on E and single stable orientation with the hydrocarbon chain facing the electrode and functional group in solution throughout the coverage region, for both the compounds. Surface excess, standard free energy of adsorption and the anodic shift of Epzc, are greater while the charge corresponding to maximum adsorption is more negative, for methyl cellosolve than for the diol.

Mechanism of charge transfer in the discontinuous metal phase of a fluidized bed electrode

From measurements of double layer capacity, collision frequency and contact time during collision, it is concluded that models for charge transfer in the discontinuous phase of fluidized bed electrode that are based on ideal particulate fluidization cannot explain metal phase resistivities, experimentally observed. Based on a literature survey it is shown that not only gas-solid but also liquid-solid fluidization is at least partially aggregative. A preliminary model for charge transfer in the discontinuous phase, based on aggregative fluidization, is derived.

ORGANO-MODIFIED CARBON ELECTRODES. I. STUDIES OF MODIFIED LAYER VIA AMIDE BONDS BY CAPACITANCE MEASUREMENTS AND ESCA

Abstract The electrochemical characteristics of chemically modified glassy carbon electrodes via amide bonds have been correlated with the results of surface analysis by X-ray photoelectron spectroscopy (ESCA). The double layer capacitance measurements were proved to be useful to determine the extent of surface modification as well as ESCA analysis.

The adsorption of potassium biphthalate at the AgI/Electrolyte solution interface from solutions of constant ionic strength

Based on the Gibbs adsorption isotherm, an equation is derived for the determination of the adsorbed amount of biphthalate from double layer capacitance measurements. In this derivation allowance is made for the dissociation and association of the biphthalate ion. The final adsorption equation is applied to the twice integrated curves of the double layer capacitance as a function of the potential at the interface between AgI and KNO 3 + K-biphthalate solutions of constant ionic strength. The best fit of the experimental results was obtained with a virial isotherm.

Deposits formed on iron during cathodic polarization in the presence of arsenic and their effect on hydrogen permeation

AbstractDeposits produced on iron and steel during cathodic polarization in the presence and absence of arsenic in acid and alkaline solutions have been studied microscopically, by electron microprobe analysis, and by double layer capacity measurements. The results of these studies are compared with permeation rates of hydrogen through rotating membranes. It is shown that the compactness of the deposits and their effect on the permeation depend on following major factors: surface condition and pre‐treatment of the cathode, pH of the electrolyte, As concentration, electrode potential. Elemental arsenic deposited on the cathode does not promote the permeation of hydrogen. On the contrary, adherent and compact films impede the entry of hydrogen into the metal phase. Arsine adsorbed on the metal surface is the main promoting species.

A study of the differential capacitance of zinc in aqueous solution with potassium silicate additions

The differential capacitance of the polycrystalline zinc electrode has been studied in aqueous solutions of KCl, KNO 3 and KOH both with and without the addition of potassium silicate. Double layer capacitance measurements can be made in KCl and KNO 3 without the interaction of OH − at low pH values < 3.0. The reduction of the nitrate ion takes place at the zinc electrode in aqueous potassium nitrate. The silicate ion is adsorbed on the zinc electrode in aqueous KOH solutions at a potential close to the dissolution potential. This results in inhibition of metal dissolution, due to limited interaction of OH − with the metal surface. The electrode resistance is increased by this adsorbed layer of silicate ion. In alkaline solution the h.e.r. is stimulated by the addition of potassium silicate.

Differential capacitance of some solid metal/aqueous-electrolyte interfaces

Electrical double-layer capacitance measurements of six solid metal electrodes, platinum gold, copper, iron, nickel and silver, in aqueous solutions of potassium chloride, bromide, iodide, nitrate and sodium sulphate were carried out with an impedance bridge, under high purity conditions. The constant capacitance obtained with these metal/solution interfaces are interpreted on the basis of Devanathan's model of the electrical double laeyr as due to the solvent contribution only, uninfluenced by specific adsorption effects in the potential range investigated.

Double layer capacity measurements involving solid electrolytes

Double layer capacity measurements involving solid electrolytes

Measurements of double layer capacity as a criterion of efficiency of corrosion inhibition on light metals in sea-water and salt solutions with and without cathodic protection

The differential capacity of AlMg-, AlMn- and AlZn-alloys during corrosion in sea-water, with and without addition of inhibitors, was determined by means of a specially made corrosion cell using an impedance bridge. Observations were made on the surfaces of alloys, with and without protective cathodic polarization immediately after immersion and after being allowed to stand in aerated sea-water, for 1, 10, 100, 300 and 1000 d. The values obtained for the differential capacity are compared to those obtained for the corrosion rate. It was found that decreasing differential capacity, also causes the decrease of the corrosion rate. This effect can be produced either by the addition of the inhibitor or by cathodic protection. The correlation between double layer capacity and the efficiency of inhibitors and cathodic polarization is interpreted as due to the formation of passive layers with adsorbed inhibitors and oxide hydrates. Thus, it has been shown that by measuring differential capacity it is possible to determine the inhibitor efficiency and cathodic prepolarization, as well as the rate of corrosion processes.

Double layer capacity measurements involving solid electrolytes

The double layer capacities of the interphases Ag, C against AgI, AgBr, Ag 4 RbI 5 have been measured over the temperature range 22–210°C. The C dl - E curves obtained have been interpreted in terms of an inner layer capacity rather than a diffuse layer capacity.

The potential and concentration dependency of the adsorption of lead(II) at the mercury-1 KCl solution interface

It is shown that when lead ions are adsorbed at the mercury-1 M KCl solution interface the interface structure changes abruptly at certain potentials at higher Pb(II) concentrations. This is demonstrated by means of double-layer capacity measurements, chronocoulometric experiments and preliminarily by the inhibition phenomena in the d.c. polarogram of Bi(III).