Personal Research Database

Full Text: J\J Ele Che46, 363.pdf

Abstract: The authors describe a surface tension measurement method suited for the double differentiation of electrocapillary curves. The procedure used for the double differentiation itself is given and discussed. For the case where organic molecules are adsorbed on the metal, the kinetics of this adsorption, as studied by impedance measurements, can explain some experimental difficulties met in surface tension measurements.

Retter, U. and Jehring, H. (1973), Adsorption kinetics at mercury electrolyte interface by analog recording at double layer admittance. Journal of Electroanalytical Chemistry, 46 (2), 375-380.

Full Text: J\J Ele Che46, 375.pdf

Abstract: The kinetics of adsorption of triethylphosphate (TÄP) and camphor were investigated in 1 M KCl solution. The method of measurement consisted in the analogue recording of selected values of phase and total double layer admittance in the frequency spectrum.

From the Cole—Cole plot of the double-layer admittance it is found that there is diffusion control at the negative desorption potential of 6.10⁻³ M TÄP in 1 M KCl while in a saturated solution of camphor in 1 M KCl both adsorption and diffusion processes control the establishment of adsorption equilibrium.

The influence of Frumkin interaction on adsorption kinetics is discussed.

Damaskin, B., Palm, U., Petyärv, E. and Salve, M. (1973), Adsorption isotherm of ions on electrodes for solutions with constant ionic strength. Journal of Electroanalytical Chemistry, 47 (1), 127-136.

Full Text: J\J Ele Che47, 127.pdf

Abstract: In the present work the equation of the isotherm for describing the specific adsorption of ions on electrodes from the system of mixed electrolytes with constant ionic strength was derived. In the derivation the buffering effect of the diffuse part of the electrical double layer, which changes by varying the ratio between the surface-active and inactive components in the system, was taken into consideration. The experimental verification of the derived isotherm was carried out on a solid bismuth electrode by studying the specific adsorption of Cs⁺ from the aqueous and methanolic solutions of the mixed electrolytes LiCl and CsCl at the different values of the constant ionic strength (0.01, 0.03, 0.1, etc.). The adsorption of Cs⁺ was studied by the differential capacity measurement method. It was found on the basis of the data obtained that the derived isotherm can successfully be applied for the quantitative characterization of the specific adsorption of Cs⁺ on bismuth only if the assumptions made in the derivation of the isotherm are valid (the absence of specific adsorption of anions in the case of recharge of the electrode by the cations). In full agreement with the equation of the isotherm the graphical plots of

log(₁{mc²}+(1−f)[logc+0.5m log m+0.5 (1−m) log(1−m)]) against ₁ give at the constant charge one common line for different ionic strengths of the systems. The parameters of these plots give the constant of the adsorption equilibrium  and the second virial coefficient B. The constant  is, within the limits of experimental error, independent of the ionic strength of the solution, both for water and methanol, and depends linearly on the charge of the electrode. The specific adsorption of Cs⁺ is stronger from methanol than from the aqueous solutions.

Anson, F.C. (1973), The evaluation of surface activities from adsorption isotherms and their utilization in kinetic analyses of electrode reactions. Journal of Electroanalytical Chemistry, 47 (2), 279-285.

Full Text: J\J Ele Che47, 279.pdf

Abstract: The kinetic equivalence of two alternative approaches for defining the surface activity coefficients of adsorbed reactants is demonstrated. A third, commonly utilized approach, which avoids the introduction of non-unit activity coefficients is also shown to yield kinetically indistinguishable results. It is argued that the definition of surface activity utilized in a recent kinetic study involving adsorbed reactants ² was inappropriate. The effects of making a kinetic analysis of the same system using modified expressions for surface activities are described.

Holub, K. (1973), The reaction of an absorbed substance with a substance transported by diffusion to the electrode: Kinetics of Langmuir adsorption without desorption coupled with diffusion. Journal of Electroanalytical Chemistry, 48 (2), 253-264.

Full Text: J\J Ele Che48, 253.pdf

Abstract: The time dependence of the surface concentration b of a substance adsorbed on the electrode, which reacts with a substance transported to the electrode by diffusion is calculated. The results are presented by means of a function 0=(b*-b)/b*(b* is the initial surface concentration) of the dimensionless parameters =ka*t or =Da*²t/b*² and =(Da*/k)^±/b*. The limiting cases of small and large values of  are discussed. It is shown that the model is equivalent to the model of Langmuir adsorption without desorption of a substance transported by diffusion to the infinite plane surface.

Manohar, G. and Sathyana, S. (1973), Effect of adsorption of omicron-cresoxide ion on kinetics of polarographic-reduction of chromate ion. Journal of Electroanalytical Chemistry, 48 (3), 383-390.

Full Text: J\J Ele Che48, 383.pdf

Abstract: The polarographic reduction of chromate ion is studied in 1 M NaOH with additions of o-cresol. It is observed that the reduction rate is depressed due to the adsorption of o-cresoxide ions formed in solution. The results are interpreted using the theory of irreversible polarographic waves with corrections applied for double layer effects. It is shown that the mechanism of inhibition of the reaction by adsorbed o-cresoxide ion is entirely one of electrostatic interaction in the adsorbed layer.

Sathyana, S. (1974), Mechanism of adsorption effects on electrode kinetics. Part I. Selection rules in case of low coverage by molecular surfactants. Journal of Electroanalytical Chemistry, 50 (2), 195-209.

Full Text: J\J Ele Che50, 195.pdf

Abstract: It is shown that the effect of adsorption of inert molecules on electrode reaction rates is completely accounted for, by introducing into the rate equation, adsorption-induced changes in both the effective electrode area as well as in the electrostatic potential at the reaction site with an additional term for the noncoulombic interaction between the reactant and the adsorbate. The electrostatic potential at the reaction site due to the adsorbed layer is calculated using a model of discretely-distributed molecules in parallel orientation when adsorbed on the electrode with an allowance for thermal agitation. The resulting expression which is valid for the limiting case of low coverages, is used to predict the types of molecular surfactants that are most likely to be useful for acceleration and inhibition of electrode reactions.

Guidelli, R. (1974), A comparison between some recent theories on the effect of ionic specific adsorption upon electrode kinetics. Journal of Electroanalytical Chemistry, 53 (2), 205-218.

Full Text: J\J Ele Che53, 205.pdf

Abstract: A theoretical expression for the rate constant of an electrode process as a function of the charge density q_i of specifically adsorbed electroinactive ions, derived by Guidelli and Foresti^I, is modified taking discreteness-of-charge effects into account, for the particular case in which the activated complex is specifically adsorbed. The modified equation is compared with analogous theoretical expressions derived by Parsons⁴ and by Fawcett and Levine⁵, so as to point out both the analogies and the main distinguishing features.

Sobkowsk, J. and Czerwiński, A. (1974), Kinetics of carbon dioxide adsorption on a platinum electrode. Journal of Electroanalytical Chemistry, 55 (3), 391-397.

Full Text: J\J Ele Che55, 391.pdf

Abstract: The kinetics of CO₂ adsorption on a platinized electrode were investigated by radiometric method. It was shown that the CO₂ adsorption is due to surface reaction with hydrogen adsorbed on the electrode. The rate of adsorption increases with the electrode potential in the range of 0.05–0.15 V and follows the second-order reaction. In the range of 0.20–0.25 V the rate of adsorption decreases according to the first-order reaction. The COOH radical is postulated as a product of CO₂ + H_ads reaction. In the range of potentials 0.05–0.20 V the maximum surface concentration of adsorbed species is ca. 9.6×10¹⁴ molecules cm⁻². The bulk concentration of CO₂ and temperature do not influence the surface concentration. The apparent heat of activation of CO₂ + H_ads reaction are 50.0 kJ mol ⁻¹ at 0.05 V and 38.5 kJ mol⁻¹ at 0.20 V, respectively.

Pospíšil, L, Kůta, J. and Volke, J. (1975), Adsorption coupled electrode kinetics of bipyridylium-based herbicides: Admittance measurement at DME in aqueous 1 M potassium fluoride. Journal of Electroanalytical Chemistry, 58 (1), 217-227.

Full Text: J\J Ele Che58, 217.pdf

Abstract: Using the admittance technique at DME the charge transfer kinetics of cation radical formation of dibenzylbipyridylium (DBBP), dimethylbipyridylium (DMBP) and ethylenebipyridylium (EBP) cations was investigated. Pronounced reactant adsorption coupled with a finite, charge transfer rate was found for DMBP and EBP. The existence of parallel pathways for charge transfer in adsorbed and non-adsorbed states was considered. The heterogeneous rate constant corresponding to the charge transfer on a completely covered surface for DBBP was determined and a possible reason for its herbicidal inactivity is suggested.

Barker, G.C. and McKeown, D. (1975), Kinetics of aniline adsorption-desorption on mercury. Journal of Electroanalytical Chemistry, 59 (3), 295-302.

Full Text: J\J Ele Che59, 295.pdf

Abstract: A preliminary study has been made of the amplitude modulation signal connected with adsorption-desorption of aniline on mercury using a 2 MHz modulation polarograph. The signal tends to be appreciably smaller than that expected for reversible adsorption-desorption in the range of potential in which molecular reorientation is an important effect. The discrepancies between theory and experiment are thought to be caused by lack of equilibrium between the interface and the solution at the interface.

Appleby, A.J. (1976), Oxygen adsorption kinetics on platinum electrodes in aqueous solution. Journal of Electroanalytical Chemistry, 68 (1), 45-48.

Full Text: J\J Ele Che68, 45.pdf

Herrmann, H.D., Wüthrich, N., Lorenz, W.J. and Schmidt, E. (1976), Kinetics of metal-ion adsorption. I. Polarization model of metal adsorbate formation. Journal of Electroanalytical Chemistry, 68 (3), 273-288.

Full Text: J\J Ele Che681, 273.pdf

Abstract: A polarisation model of Me^z+ adsorption at solid foreign electrodes is proposed, considering Me^z+ transfer and surface diffusion to be the rate determining steps. Surface heterogeneity is accounted for by assuming the substrate to be composed of individual homogeneous regions of limited size, the Me^z+ transfer occurring preferentially at line discontinuities such as grain or subgrain boundaries or step lines of atomic height. An explicit expression for the potentiostatic charge—time curve is derived. Short-time approximations of both potentiostatic and galvanostatic response signals are given as convolution products of the input functions with power series of t^1/2. All odd powers of t^1/2 disappear in the case of Dolin—Ershler RC-behaviour without surface diffusion control. The t^−1/2 and t^1/2 terms of the potentiostatic and galvanostatic series, respectively, are present only if adsorption equilibrium is established instantaneously at the line discontinuities. From the t⁰ and t terms, respectively, the overall transfer resistance may be calculated.

Herrmann, H.D., Wüthrich, N., Lorenz, W.J. and Schmidt, E. (1976), Kinetics of metal-ion adsorption. II. Galvanostatic impulse measurements of silver, lead and thallium adsorbates on gold electrodes. Journal of Electroanalytical Chemistry, 68 (3), 289-301.

Full Text: J\J Ele Che68, 289.pdf

Abstract: The kinetics of the metal ion adsorption of Ag⁺, Tl⁺ and Pb²⁺ on polycrystalline and (111) orientated monocrystalline gold electrodes were investigated using a low-level short-time polarization technique. In the present case the systems were potentiostatically prepolarized under steady state equilibrium conditions. The perturbation was realized by galvanostatic square pulses. The observed overpotential—time transients were analyzed by polynomial curve fitting. The results can be interpreted in terms of the developed polarization model [1] : (1) the process of metal ion adsorption is not reversible; (2) the hindrance is caused by charge transfer and can also be influenced by surface diffusion of the adsorbed metal ion species. In the case of Ag⁺ and Pb²⁺ the calculated mean values of the exchange current densities of the sorption processes are lower than the exchange current densities of the corresponding metal ion electrodes and they do not depend markedly on the potential. The data obtained are discussed.

Więckowski, A. (1977), Kinetic isotope effects between light and heavy-water in hcooh and CH₃OH adsorption and oxidation on Pt mechanistic considerations. Journal of Electroanalytical Chemistry, 78 (2), 229-241.

Full Text: J\J Ele Che78, 229.pdf

Abstract: Kinetic isotope effects between H₂O and D₂O in HCOOH and CH₃Oh adsorption and oxidation on platinized Pt electrodes have been studied in sulphuric acid electrolyte. The normal kinetic effects have been found for CH₃OH adsorption and for the oxidation of the chemisorbed species, the inverse isotope effect for HCOOH adsorption has been detected. The latter observation, as well as highly negative value of entropy of activation and the pH dependence, support the “reduction” mechanism of HCOOH adsorption described previously. Solvent isotope effects contribute to CH₃OH as well as HCOOH adsorption. The observed low isotope effect for the oxidation of chemisorbed species is interpreted as an evidence that adsorbed water molecules are the very oxygen containing species involved in the oxidation.

Więckowski, A., Sobkowski, J. and Zelenay, P. (1977), Potential dependence and kinetics of hcooh adsorption on rhodium electrodes. Journal of Electroanalytical Chemistry, 84 (1), 109-116.

Full Text: J\J Ele Che84, 109.pdf

Abstract: The formic acid adsorption on an electrochemically prepared rhodium electrode has been studied by the radiochemical method. Electrochemical properties of the rhodium electrode surface in 0.5 M H₂SO₄ have been investigated by cyclic voltammetry. It has been shown that starting from E = 0.20 V the rate of HCOOH adsorption is markedly potential dependent being practically independent of the electrode potential up to E = 0.20 V. It seems that the HCOOH adsorption process may be explained on the basis of the two-sites kinetics model. The data obtained for HCOOH adsorption on a rhodium electrode have been compared with those for a platinum electrode reported previously.

Žežula, I, Rychnavská, V. and Alexyová, E. (1978), Effect of ionic-strength of supporting electrolyte on electroreduction kinetics of anions influenced by specific adsorption. Journal of Electroanalytical Chemistry, 86 (2), 433-437.

Full Text: J\J Ele Che86, 433.pdf

Gurevich, Yu.Ya. and Kharkats, Yu.I. (1978), On the temperature behaviour of an adsorption system described by a Frumkin-type isotherm. Journal of Electroanalytical Chemistry, 86 (2), 245-258.

Full Text: J\J Ele Che86, 245.pdf

Abstract: A theory is developed describing stepwise coverage changes with temperature in a system of adsorbed species interacting on the surface. The temperature pattern of coverage is shown to be significantly more interesting and variegated than the concentration pattern. The existence of double transitions in the system is predicted and the conditions for their realization are analyzed.

Weber, J., Samec, Z. and Mareček, V. (1978), Effect of anion adsorption on kinetics of Fe³⁺-Fe²⁺ reaction on pt and au electrodes in HClO₄. Journal of Electroanalytical Chemistry, 89 (2), 271-288.

Full Text: J\J Ele Che89, 271.pdf

Abstract: The kinetics of the Fe³⁺/Fe²⁺ reaction was studied on Pt and Au rotating disk electrodes in 0.5 M HClO₄ solutions. It was found that the rate constant is trongly affected by adsorption of traces of anionic impurities. Consequently, the solution was purified by adsorption on a large platinum electrode. The measured current was corrected for the effect of the ₂ potential. The actual rate constant value for the Fe³⁺/Fe²⁺ reaction on a Pt electrode was 1.5×10⁻³ cm s⁻¹ and on an Au electrode, 7.9×10⁻³ cm s⁻¹; the corresponding reorganization energy values were 120 kJ mol⁻¹, respectively. The effect of the adsorption of chloride, bromide and sulphate anions in increasing the rate of the reaction was studied. The rate constant of the reaction increases approximately exponentially with the coverage of the electrode by anions. The mechanism by which the anions increase the reaction rate was discussed.

Pospíšil, L, Kůta, J., Peter, F. and Gross, M. (1978), Admittance measurements of kinetic and adsorption parameters of anodic mercury complex-formation with macrobicyclic (222) ligand in propylenecarbonate and dimethylformamide. Journal of Electroanalytical Chemistry, 90 (2), 251-259.

Full Text: J\J Ele Che90, 251.pdf

Abstract: Admittance measurements were applied to investigation of the charge-transfer rate and mechanism of anodic complex formation between mercury and macrobicyclic ligand (222) as well as to the cathodic reduction of Hg²⁺-(222) complex formed in the bulk. From measurements in PC and DMF using adsorbable and non-adsorbable base électrolyte anions it was shown that the reactant adsorption effects are observable only if adsorption of ClO⁻₄ and (222) takes place at the same time. Corresponding charge-transfer rates were evaluated and potential dependence of the adsorption capacity for two ligand concentrations was given. At the half-wave potential apparent rate constants k^0.5 listed below were found (data from Fig. 9).

Badiali, J.P. and Goodisman, J. (1978), Thermodynamics and statistical mechanics of the ideally polarizable electrode: Gibbs isotherm and surface tension. Journal of Electroanalytical Chemistry, 91 (2), 151-171.

Full Text: J\J Ele Che91, 151.pdf

Abstract: A definition of the ideally polarisable electrode which allows a general statistical mechanical treatment is given, comparisons with the usual thermodynamic approach being made. It is shown that, with this definition, the system behaves as a pure capacitance to an imposed alternating potential of sufficiently low frequency. The equilibrium states of the system are described by the grand canonical distribution. Thermodynamic functions, given in terms of the grand canonical partition function, can be computed in molecular terms. In particular, general expressions for the surface tension and the pressure are obtained, and compared to those proposed by various authors. The separation of the pressure into electrical and non-electrical parts is analyzed. Expressions are given for the electrochemical potentials of charged and of dipolar species. With these microscopic definitions, the Gibbs adsorption isotherms and the Lippmann equation are derived. For several simple models, including that of Gouy and Chapman for an ionic solution and a metal electrode, these relations are explicitly considered. The inadmissability, in a coherent model, of reducing the solvent to a medium of fixed dielectric constant, is emphasized.

Sadkowski, A. (1979), Determination of the heterogeneity factor in the Frumkin adsorption isotherm from the width of capacity peaks. Journal of Electroanalytical Chemistry, 97 (2), 283-286.

Full Text: J\J Ele Che97, 283.pdf

Vassiliev, Yu.B., Bagotzky, V.S., Khazova, O.A., Cherny, V.V. and Meretsky, A.M. (1979), Mechanism of adsorption, electroreduction and hydrogenation of compounds with ethylenic bonds on platinum and rhodium. Part I. Kinetics of adsorption and electroreduction. Journal of Electroanalytical Chemistry, 98 (2), 253-272.

Full Text: J\J Ele Che98, 253.pdf

Abstract: The influence of various factors (concentration, potential, solution, pH, surface coverage with the organic substance, temperature, etc.) on the adsorption and electroreduction of maleic acid and other ethylene compounds on platinum and rhodium has been investigated. Quantitative comparison of the results of adsorption and kinetic measurements carried out under similar conditions has made it possible to elucidate the mechanism of electroreduction. It is shown that the rate-determining step of the electroreduction process of maleic acid is the interaction of the chemisorbed particle of maleic acid with the adsorbed hydrogen which is formed at the preceding rapid stage of hydrogen ion discharge. Considerable differences in the rates of electroreduction of various ethylene compounds at a constant volume concentration result from a strong influence of substituents on the rate and value of the adsorption of a given ethylene compound. The presence of substituents has only a very weak influence on the electroreduction rate constant as such.

Kashti, S. and Kirowa-Eisner, E. (1979), The effects of adsorption conformation of intermediates on the kinetic parameters of an electrode process mechanism of the electroreduction of chloropyridines on the DME. Journal of Electroanalytical Chemistry, 103 (1), 119-135.

Full Text: J\J Ele Che103, 119.pdf

Abstract: The mechanism of reduction of 2- and 4-chloropyridine and 2,3-dichloropyridine in ethanol-water solvent was investigated at the DME. The electrode processes were studied by measurements of Tafel slopes, reaction orders and pH effects. Although the reduction process, involving the positions 2 and 4 to the nitrogen should proceed by the same mechanism, different Tafel slopes were observed for the investigated compounds. These differences and the absolute values of the Tafel slopes are explained by the combined adsorption isotherm on the basis of the adsorption conformation of the intermediates. The proposed mechanism involves: (a) first protonation and electronation in a quasi-equilibrium step resulting in an adsorbed chloropyridine radical (intermediate I) parallel to the electrode surface; (b) cleavage of the C---Cl bond in the rate-determining step, resulting in an adsorbed cation radical (intermediate II) which by analogy to -mers and dimers can be parallel or perpendicular to the electrode, depending on the electrode charge. In the perpendicular orientation of intermediate II, the three investigated compounds have different adsorption conformations, yielding different Tafel slopes as a result of differences in the adsorption parameters m and ∂_x/∂_M. In the parallel orientation of intermediate II the monochloropyridines have the same adsorption parameters and hence the same Tafel slope. The Tafel slopes computed via the combined adsorption isotherm are in agreement with the experimental values.

Sadkowski, A. (1979), Electrochemical adsorption reaction (EAR). Part I. Comparative analysis of various pulse methods in the study of equilibrium and kinetics of electrochemical adsorption reactions. Journal of Electroanalytical Chemistry, 105 (1), 1-23.

Full Text: J\J Ele Che105, 1.pdf

Abstract: The theoretical analysis of electrochemical adsorption reaction (EAR) under condition of linear and non-linear pulse experiment is given. Pure activational control is assumed, with the simple kinetic equation compatible with Frumkin adsorption isotherm. The criteria of determination of the equilibrium and kinetic parameters of EAR are proposed. Advantages of the use of the dimensionless variables and formulae in electrode kinetics are demonstrated.

Krylov, V.S. Kiryanov, V.A. and Fishtik, I.F. (1980), Effect of specific adsorption of ions on the kinetics of electrode processes. Journal of Electroanalytical Chemistry, 109 (1-3), 115-124.

Full Text: J\J Ele Che109, 115.pdf

Abstract: The problem of statistical averaging of the probability of the elementary act of the electron transfer electrochemical reaction at the metal/solution interface in the presence of specifically adsorbed electroinactive ions is considered. The analytical expressions for the polarization characteristic of the electrode are obtained for the cases of localization of the centers of the ionic reagents in the reaction state, both inside the compact and the diffuse parts of the double layer. Within the framework of the developed theory the available experimental data on the hydrogen-ion discharge on mercury in the presence of halogenide ions are analyzed.

? Karolczak, M.P. (1981), Some remarks on the generalized adsorption isotherm. Journal of Electroanalytical Chemistry, 122, 373-376.

Full Text: 1981\J Ele Che122, 373.pdf

? Vollhardt, D., Modrow, U., Retter, U., Jehring, H. and Siegler, K. (1981), Investigations on adsorption kinetics of sodium decyl sulfate at the mercury/electrolyte interface. Part I. Examination of different models for the adsorption process by non-linear regression analysis. Journal of Electroanalytical Chemistry, 125 (1), 149-156

Full Text: 1981\J Ele Che125, 149.pdf

Abstract: The frequency dependence of the electrode admittance of sodium decyl sulphate solutions above the critical micellar concentration was measured at the more negative ad/desorption potential. The following models, out of a series of possible models, could be selected by non-linear regression: one process with diffusion control; two diffusion-controlled processes occurring in parallel; two parallel processes, one of them diffusion-controlled the other adsorption -controlled.

Keywords: Adsorption, Models, Sodium, Sulfate

Schirmer, H. and Baumgartel, H. (1991), The specific adsorption of halides on mercury in nonaqueous acetonitrile. Journal of Electroanalytical Chemistry, 316 (1-2), 235-253.

Full Text: J\J Ele Che316, 235.pdf

Abstract: The adsorption behaviour of various tetraalkylammonium halides R4NX (R = Et, Bu; X = I-, Br) and sodium iodide at the mercury/acetonitrile interphase has been investigated employing capacity measurements and measurements of the potential of zero charge at variable ionic strength. The results indicate strong specific adsorption of halide ions in the range between negative and positive electrode charges. For NaI, a more detailed study of the adsorption process based on the virial isotherm was performed including the evaluation of the standard Gibbs energy of adsorption and the interaction parameter. Moreover, the distance ratio (x2-x1)/x2 and the Esin-Markov coefficients could be estimated. From differences between the Esin-Markov coefficients determined for all salts under investigation, a counter-ion effect with respect to the halide adsorption could be deduced. The specific adsorption of halide ions in acetonitrile will be discussed, particularly with regard to the influence of solvent and ion association.

Keywords: Vapor-Pressure Measurements, Gibbs Free-Energies, Electrolyte-Solutions, Electroreflectance Investigations, Tetraalkylammonium Salts, Thermodynamic Parameters, Electrosorption Valency, Gold Determination, Single-Crystals, Mixed-Solvents

Bockris, J.O.M. and Jeng, K.T. (1992), In-situ studies of adsorption of organic compounds on platinum electrodes. Journal of Electroanalytical Chemistry, 330 (1-2), 541-581.

Full Text: J\J Ele Che330, 541.pdf

Abstract: Studies of the electrosorption of organic compounds on polycrystalline platinum electrodes were carried out in 0.01 M HCl solution. In-situ techniques, i.e. radiotracer measurements, ellipsometry and Fourier transform infrared spectroscopy, were used in the measurements. Good agreement in results was obtained between these techniques. The electrosorption process was found to be slow, but a bell-shaped coverage fJ versus potential V curve was generally obtained in the double-layer region with a submonolayer adsorption. The difference between the potential of zero charge and the maximum, of adsorption is about f 0.1 V. A water competition adsorption model, based on the statistical mechanics approach, was proposed. Both lateral interactions between adsorbed species and the effect of heterogeneity of the electrode surface were taken into account. The standard state for the adsorption was found by equating f(O) to unity. A Temkin-type isotherm was obtained in all cases, indicating a strong effect of heterogeneity of the surface. Also, Elovich-type kinetics were found and the adsorption activation energy was calculated. The bonding strength between the adsorbate and the electrode surface was found to be around 20-40 kcal/mol which is comparable with that measured in the gas phase. The adsorbed species generally adopts a flat orientation. Electropolymerization for some phenyl species may occur at a potential more positive than 0.9 V vs. the standard hydrogen electrode.

Blankenborg, S.G.J., Sluytersrehbach, M. and Sluyters, J.H. (1993), Charge-transfer kinetics of a system with weak reactant adsorption studied by the combination of demodulation and impedance voltammetry. Part 1. The Tl⁺/Tl(Hg) reaction in 1 M HClO₄ at the dropping mercury electrode. Journal of Electroanalytical Chemistry, 349 (1-2), 255-272.

Full Text: J\J Ele Che349, 255.pdf

Abstract: Mathematical expressions are derived and discussed with which the second-order demodulation method, combined with the first-order impedance method, can be used to unravel the effects due to diffusion, charge transfer and reactant adsorption simultaneously controlling an electrode reaction. By assuming that the adsorption is relatively weak, approximations are introduced in order to keep the mathematics tractable. The validity of the treatment is verified by a study of the Tl⁺/Tl(Hg) system in 1 M HClO₄ supporting electrolyte.

The Tl⁺ adsorption is described by the Langmuir adsorption isotherm, with the standard adsorption energy linearly dependent on the electrode potential. The charge-transfer process follows simple Butler-Volmer kinetics, with the transfer coefficient a close to 0.5 and the standard rate constant k_s = 1.2 cm s^-1 just above the detection limit of the impedance method. All parameters determined are independent of the Tl⁺ concentration, which confirms the internal consistency of the treatment.

Keywords: Admittance Analysis, Reduction, Ac, Polarography, Cadmium(II), Behavior, NaClC₄, Ions

Wieckowski, A. (1993), Comments on the paper entitled In situ studies of adsorption of organic compounds on platinum electrodes, by J. O’M. Bockris and K.T. Jeng. Journal of Electroanalytical Chemistry, 352 (1-2), 313-320.

Full Text: J\J Ele Che352, 313.pdf

Keywords: Radiotracer Method, Acetic-Acid, Surfaces, Pt(111), Smooth

Pérez, M., Barrera, M., Andreu, R. and Molero, M. (1993), Adsorption of malonate and succinate at the Hg/aqueous solution interphase. Journal of Electroanalytical Chemistry, 361 (1-2), 239-249.

Full Text: J\J Ele Che361, 239.pdf

Abstract: The surface excesses of malonate and succinate are derived from differential capacity, potential of zero charge (pzc) and interfacial tension measurements. When the electrode is very negatively charged, the interphase is described well by a simple electrostatic model assigning different distances of closest approach to the electrode for Na⁺ (lambda = 1.6 angstrom), succinate (lambda = 1.6 angstrom) and malonate (lambda-4.4 angstrom). When the electrode is positively or not very negatively charged, malonate and succinate are specifically adsorbed on Hg. In both cases the adsorption is described well by a virial isotherm, having similar adsorption parameters. The adsorption of succinate on Hg when compared with earlier results in the literature on (210) and (311) gold faces follows the sequence Au(311) > Au(210) > Hg. Integral capacities and electrosorption valency are also calculated and analyzed, suggesting that (a) at potentials close to or more negative than the pzc, specifically adsorbed malonate and succinate place their electrical charges in the vicinity of the outer Helmholtz plane and probably do not make direct contact with the electrode, and (b) at potentials more positive than the pzc, succinate progressively replaces water molecules in contact with the electrode and probably lies flat on the metal surface, while malonate retains its carboxylate groups partially oriented towards the solution.

Keywords: Electrical Double-Layer, Aqueous-Electrolyte Interface, Constant Cationic Strength, Gouy-Chapman Theory, Electrosorption Valency, Activity-Coefficients, Dicarboxylic Ions, Mercury-Electrode, Anions, Parameters

Guaus, E. and Sanz, F., Sluyters-Rehbach, M. and Sluyters, J.H. (1994), Study of reaction adsorption in the system Cd(II)KBr (1M)/Hg by chronocoulometry. Journal of Electroanalytical Chemistry, 368 (1-2), 307-314.

Full Text: J\J Ele Che368, 307.pdf

Abstract: Using the exact theoretical equations derived to describe the response in single-step chronocoulometry (SSC) and a reported method for correction of the double layer charge, the chronocoulometric response of the Cd(II) + KBr(l M)/Cd(Hg) system is analyzed. The applicability of our theoretical equations and the quantitative use of the chronocoulometric technique are demonstrated. The potential step starts in the pre-faradaic potential range and ends at some potential inside the d.c. polarographic wave. From the charge response obtained with steps ending at the limiting current plateau, the value of the reactant surface excess corrected for double layer charging, was calculated. A detailed analysis of the dependence on the electrical variable ^m of the reactant surface excess led us to propose a plausible adsorption isotherm to which both the Cd(II)-complex species and the bromide anion adsorbed on the electrode contribute.

Guaus, E., Sanz, F., Sluyters-Rehbach, M. and Sluyters, J.H. (1995), Competitive adsorption versus surface complexation as models for the simultaneous adsorption of metal complexes and free ligands. Journal of Electroanalytical Chemistry, 385 (1), 121-134.

Full Text: J\J Ele Che385, 121.pdf

Abstract: A statistical thermodynamical approach to the study of anion-induced adsorption of Cd(II) from halide solutions is presented. The simultaneous adsorption of metal complex and ligand is introduced in the isotherms by considering two possible mechanisms-competitive adsorption and surface complexation. These isotherms have been tested for the system Cd(II) in KBr at several ionic strengths. The experimental surface excesses of Cd(II) calculated from single-step chronocoulometry can be simulated, giving an explanation for the desorption of the metal complex at positive potentials. Also, the change in ligand adsorption promoted by the adsorption of the metal complex has been calculated. Both approaches lead to the conclusion that the anionic tricoordinate metal complex CdBr₃^-and the tetracoordinate CdBr₄^2-are the adsorbed species on the electrode surface, with CdBr₄^2-dominating at higher bromide concentrations.

Keywords: Statistical Thermodynamics, Mathematical Models, Simultaneous Adsorption, Metal Complexes, Free Ligands, Induced Reactant Adsorption, Dropping Mercury-Electrode, Anion-Induced Adsorption, Scanning Tunneling Microscopy, Normal Pulse Polarography, Theoretical Treatment, Cadmium(II) Ions, Labile Metal, Admittance, Reduction

Ardizzone, S. and Orlandi, M. (1995), Adsorption of alkyl benzenesulfonates at the ZrO₂-vertical-bar-solution interface. Journal of Electroanalytical Chemistry, 391 (1-2), 181-185.

Full Text: J\J Ele Che391, 181.pdf

Abstract: Adsorption measurements of an anionic surfactant (p-n-sodium-octyl-benzenesulfonate) have been performed at the oxide solution boundary of zirconia suspensions. Three different isotherms have been obtained by varying the conditions of electrification of the oxide surface. The experimental isotherms are discussed in the light of literature data and analyzed on the basis of the Frumkin-Fowler-Guggenheim adsorption equation. Either attractive or repulsive lateral interaction terms are obtained depending on the oxide surface charge (and potential) and on the concentration of the base electrolyte.

Keywords: Surfactants, Interfacial Chemistry, Adsorption, Alkyl-Benzenesulfonates, ZrO₂, Electrolyte Interface, Water Interface, Organic Cations, Oxide Surfaces, Surfactants, Temperature, Particles, Ions

Calvente, J.J., Kováčová, Z., Andreu, R. and Fawcett, W.R. (1996), The role of the metal in determining electrosorption valency in the case of strong molecular adsorption at the electrode vertical bar solution interface. Journal of Electroanalytical Chemistry, 401 (1-2), 231-235.

Full Text: J\J Ele Che401, 231.pdf

Notes: highly cited

? Pang, D.W., Zhang, M., Wang, Z.L., Qi, Y.P., Cheng, J.K. and Liu, Z.Y. (1996), Modification of glassy carbon and gold electrodes with DNA. Journal of Electroanalytical Chemistry, 403 (1-2), 183-188.

Full Text: 1996\J Ele Che403, 183.pdf

Abstract: The modification of glassy carbon and gold electrodes with DNA by adsorption or covalent immobilization in a mono- or submonolayer has been investigated using the couple Co(bpy)(3)(3+/2+) as an indicator. It has been found that when the solution containing double stranded or single stranded DNA is evaporated to dryness, dehydrated DNA molecules can be irreversibly adsorbed on the surfaces of glassy carbon electrodes, in an amount close to that of the saturated adsorptive monolayer. The DNA-adsorbed layer on glassy carbon electrodes is unstable to bases, but stable to 1 M HCl solution. The adsorption of DNA on the electrodes can be evaluated from the increase in the peak current, the decrease in the value of Delta E(p), and the negative shift in the value of E(o’) for the Co(bpy)(3)(3+/2+) couple. DNA is very strongly adsorbed on the oxidized surfaces of glassy carbon electrodes, and the adsorptive layer is very stable towards heating. The covalent immobilization of DNA directly onto the electrode surfaces is impossible due to considerable steric hindrance; but if the active groups (sites) on the electrode surfaces are elongated with other suitable molecules, the covalent immobilization of DNA becomes possible on the electrode surfaces. The quantity of covalently immobilized DNA at the electrodes reported in the paper is about 31% of the saturated monolayer.

Keywords: DNA-Modified Electrode, Electrochemical DNA Biosensor, Gene Detection, Adsorption of DNA, Immobilization of DNA, Monolayer, Hybridization, Immobilization, Binding

Keywords: Metal, Interface Structure, Electron Work Function, PZC, Ag(111)

Hara, K., Tsuneto, A., Kudo, A. and Sakata, T. (1997), Change in the product selectivity for the electrochemical CO₂ reduction by adsorption of sulfide ion on metal electrodes. Journal of Electroanalytical Chemistry, 434 (1-2), 239-243.

Full Text: J\J Ele Che434, 239.pdf

Abstract: The effects of adsorbed sulfide ion (S^2-) formed on metal electrodes in the electrochemical reduction of CO₂ under high pressure were investigated. The selectivity for the reduction products changed markedly with the Na2S treatment of metal electrodes. In the case of a Cuelectrode, the faradaic efficiency for methane formation decreased remarkably from 36% to 2%, whereas that for C₂ components (ethylene and ethanol) increased from 13% to 25% due to the Na₂S treatment. The faradaic efficiencies for formic acid and hydrogen formation also increased with the treatment. A similar change in the product selectivity was also observed in the electrolysis with addition of Na₂S into the aqueous electrolyte. A study of the current-potential curve suggested that adsorbed sulfide ion prevented the formation of adsorbed CO and thus changed the product selectivity.

Baars, A., Aoki, K. and Numata, Y. (1997), Catalysis and inhibition of charge transfer rate of cadmium ions at a partially blocked dropping mercury microelectrode by butanol. Journal of Electroanalytical Chemistry, 436 (1-2), 133-140.

Full Text: J\J Ele Che436, 133.pdf

Abstract: A classical problem of the effects on charge transfer rate constants by foreign adsorbed species was re-investigated by the dropping mercury microelectrode technique with rapid and reproducible response. A question is why reaction rates generally have a non-linear relation with the fraction of the blocked electrode area. Reduction rate constants of cadmium ions in the presence of 1-butanol were evaluated in 1 mol dm^-3 KF as a function of coverage of 1-butanol and the electrode potential, where the coverage obeyed a Frumkin type isotherm including a quadratic dependence of the potential. The rate constants showed a non-linear relation with the coverage. The rate was enhanced by the adsorption at potentials E < -0.85 V vs. SCE whereas it was blocked at E > -0.75 V. A statistical model interpreting both the catalytic and the inhibiting effects was proposed, in which the cadmium ion interacts with several adsorbed 1-butanol molecules at the nearest neighboring reaction sites on the electrode surface. The model gave a non-linear relation with the coverage as a function of the interaction energy. The interaction energy was estimated from another statistical mechanical model of an adsorbed rigid dipole in the electric field on the assumption that the dipole interacts coulombically with the cadmium ion. The model was analyzed quantitatively and explained the experimental data approximately. (C) 1997 Elsevier Science S.A.

Keywords: Adsorption of Butanol, Reaction Rate Constants of Cadmium Ions, Dropping Mercury Electrodes, Partially Blocked Electrodes, Adsorption Isotherm, Nearest Neighbor Interaction, Dm-Mu-E, Electrode-Reactions, Adsorption, Interface, Step, KF

Mukerjee, S. and McBreen, J. (1998), Effect of particle size on the electrocatalysis by carbon-supported Pt electrocatalysts: An in situ XAS investigation. Journal of Electroanalytical Chemistry, 448 (2), 163-171.

Full Text: J\J Ele Che448, 163.pdf

Abstract: In situ X-ray absorption studies were done in 1M HClO₄ with and without 0.3 M MeOH, on several well-defined carbon-supported Pt electrocatalysts with particle sizes in the range of 25 to 90 Angstrom. Data were obtained at several potentials in the range of 0.0 to 1.14V vs. RHE. The results show that as the particle size is reduced below 50 Angstrom, the strength of adsorption of H, OH and C-1, moieties such as CO is increased. The strong adsorption of OH explains the reduced specific activity for oxygen reduction on small particles. The reduced activity for methanol oxidation on the small particles is due to a combination of the increased strength of adsorption of both CO and OH. The strong adsorption of H at negative potentials on small Pt particles is sufficient to induce reconstruction and morphological changes in the Pt particles. Both XANES and EXAFS data on a 53 Angstrom particle at 0.84V indicate that formation of PtOH is the rate determining step in the oxidation of methanol. All these affects are due to an increase in the number of Pt sites with low coordination on the small particles. (C) 1998 Elsevier Science S.A. All rights reserved.

Keywords: Carbon-Supported Pt, Electrocatalysis, Particle Size, X-Ray Absorption Spectroscopy, Methanol Oxidation, X-Ray-Absorption, Oxygen Reduction, Platinum Particles, Electronic-Structure, Metal-Catalysts, Oxidation, Methanol, Acid, Clusters, Alloys

Puy, J., Torrent, M., Monné, J., Cecília, J., Galceran, J., Salvador, J., Garcés, J.L., Mas, F. and Berbel, F. (1998), Influence of the adsorption phenomena on the NPP and RPP limiting currents for labile metal-macromolecule systems. Journal of Electroanalytical Chemistry, 457 (1-2), 229-246.

Full Text: J\J Ele Che457, 229.pdf

Abstract: The impact of adsorption effects on limiting currents obtained in reverse pulse (RPP) and normal pulse polarography (NPP) is analysed critically for induced reactant adsorption systems with any ligand to metal ratio. Qualitative explanations in terms of the concentration profiles are provided. We demonstrate that, for labile systems, no influence on the RPP limiting current can be found from the complex adsorption. However, ligand adsorption increases the RPP limiting current, this influence decreasing as the total metal concentration decreases. So, RPP normalised limiting current values (phi) are suggested to improve the fitting of the stability constant at very low total metal concentrations. If the total ligand concentration is chosen for maximum sensitivity, the remaining effect of the ligand adsorption leads to a bias in the stability constant of less than 14%, provided that the diffusion coefficient of the complex and ligand is 20-fold lower than the diffusion coefficient of the metal ion. Because the limiting NPP and RPP currents are equal for any ligand to metal ratio and without adsorption, approximate expressions derived for NPP facilitate the determination of the stability constant from the phi versus total metal concentration plot. This procedure is applied to some experimental results of Zn and Cd complexed with poly (methacrylic) acid.

Smoliński, S. and Sobkowski, J. (1999), Adsorption of sulfate ions on monocrystalline copper electrodes: The structural effects. Journal of Electroanalytical Chemistry, 463 (1), 1-8.

Full Text: J\J Ele Che463, 1.pdf

Abstract: Adsorption of sulfate ions on the three basal planes of monocrystalline copper electrodes in 0.1 M HClO₄ was studied by radiometric and electrochemical methods. Also, the copper electrode activity for hydrogen ion discharge was investigated. To check the order of copper surfaces the underpotential deposition of lead was applied. Adsorption of sulfate ions on all four surfaces was found to be reversible with respect to the potential and bulk solution concentration of sulfate. Adsorption isotherms were determined radiometrically. The Gibbs energy of adsorption was calculated by fitting the Henry, Frumkin and virial isotherm equations to the experimental data points. The limiting surface concentration of sulfate ions decreases in the sequence: Cu(111) > Cu(110) > Cu(poly) > Cu(100). The highest value of surface concentration of sulfate for the (111) plane can be accounted for by a match between the tetrahedral structure of the anion and the trigonal distribution pattern of the surface atoms of copper on this plane. (C) 1999 Elsevier Science S.A. All rights reserved.

Keywords: Adsorption, Monocrystalline Electrodes, Copper, Sulfate Ion, Radiometry, Isotherms, Sulfuric-Acid-Solution, Au(111) Electrode, Neutral Media, SO₄^2-Ions, Adatoms, Radiotracer

Ju, H.X. and Leech, D. (2000), Electrochemical study of a metallothionein modified gold disk electrode and its action on Hg²⁺ cations. Journal of Electroanalytical Chemistry, 484 (2), 150-156.

Full Text: J\J Ele Che484, 150.pdf

Abstract: A novel protein monolayer modified electrode has been prepared by the self-assembly of metallothionein (MT) at a gold disk electrode. The properties of MT in Tris-HCl buffer and in the monolayer are studied by using cyclic voltammetry and differential pulse voltammetry with a gold disk electrode. In the negative sweep, the voltammogram of MT in buffer shows two small peaks and different electrochemical behaviour from that at a mercury electrode. Cd²⁺ complexed to the thionein can easily be replaced by Hg²⁺ ions, and Hg²⁺ ions can firmly adsorb in the MT monolayer with a saturation coverage of (2.78±0.29)×10^-10 mol cm^-2 This behaviour has been used to preconcentrate trace Hg²⁺ for its determination by cathodic stripping differential pulse voltammetry. The cathodic stripping peak current is proportional to Hg²⁺ concentration in the range of 0.15-3 µM and the detection limit is ca. 0.08 µM (16 ppb) with a 2 min open circuit accumulation step. The relative standard deviation is 7.2% at 0.4 µM Hg²⁺ concentration (n = 4). At higher concentration the adsorption of Hg²⁺ exhibits a response similar to that expected for a Langmuir adsorption isotherm with the stability constant of (4.0±0.2)×10⁵ M^-1. (C) 2000 Elsevier Science S.A. All rights reserved.

Keywords: Chemically Modified Electrodes, Self-Assembled Monolayer, Metallothionein, Gold Disk Electrode, Determination of Hg(II), Cathodic Stopping Voltammetry, Differential-Pulse Polarography, 56-61 MT-I, Cyclic Voltammetry, Cadmium-Metallothionein, Thiolate Clusters, Carbon Electrodes, Zinc, Behavior, Mercury, Molecules

Zelić, M. and Lovrić, M. (2003), The influence of electrolyte concentration on the parameters of the Frumkin isotherm in the Cd²⁺-I^- system. Journal of Electroanalytical Chemistry, 541, 67-766.

Full Text: J\J Ele Che541, 67.pdf

Abstract: The influence of ionic strength (1-6 mol l^-1 NaClO₄) on the parameters of adsorption isotherm(s) was studied using Cd²⁺-I^- system as a model. Results, based on differential pulse polarographic measurements, simulation of polarograms and signal fitting procedure, indicate that the maximum surface concentration = (Gamma_max = 110^-10 to (2.2 0.2)10^-10 mol cm^-2), adsorption constant (beta = 3.110⁵ to (1.55 0.35)10⁷ 1 mol^-1) and Frumkin coefficient (a = 0 to (0.5 0.1)) all increase with increasing electrolyte concentration. According to the model calculations, parallel increase of the adsorption constant and Frumkin coefficient should have the opposite influences on the shape of the reduction signal. In the system of interest, however, the former seems to be more important than the latter. As a result, gradual transformation of a single symmetrical peak to two close peaks can be observed on real polarograms at increasing electrolyte concentration. (C) 2002 Elsevier Science B.V. All rights reserved.

Keywords: Cadmium, Iodide, Adsorption Isotherm, Supporting Electrolyte, Differential Pulse Polarography, Simulation, Anion-Induced Adsorption, Dropping Mercury-Electrode, Bromide-Induced Adsorption, Pulse Polarography, Ionic Strengths, Cadmium(II), Voltammetry

Holzapfel, M., Martinent, A., Alloin, F., Le Gorrec, B., Yazami, R. and Montella, C. (2003), First lithiation and charge/discharge cycles of graphite materials, investigated by electrochemical impedance spectroscopy. Journal of Electroanalytical Chemistry, 546, 41-50.

Full Text: J\J Ele Che546, 41.pdf

Abstract: In this study graphite has been characterised by electrochemical impedance spectroscopy (EIS) using a three electrode coin cell. The initial lithiation shows that lithium insertion can be modelled using the Langmuir insertion isotherm as well as the Frumkin insertion isotherm for very low insertion levels. A description of the equivalent circuits used to fit the high frequency (HF) part of the impedance spectra is presented based on chi-square values and the uncertainties in the values of parameters. The HF signature, that appears at the beginning of lithiation does not show behaviour associated solely with the formation of a passivation film but indicates that contact problems related to the electrode volume must be considered too. The study describes the first charge/discharge cycles and shows that the observed phenomena are mostly reversible. (C) 2003 Elsevier Science B.V. All rights reserved.

Keywords: AC Impedance, Graphite, Passivation Film, Intercalation, Lithium-Ion, Battery, Lithium Ion Intercalation, Electroanalytical Behavior, Pyrolytic-Graphite, Carbon Electrode, Batteries, Insertion, Diffusion, Kinetics, Anodes