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Juan R. Castillo - One of the best experts on this subject based on the ideXlab platform.

  • Electrochemical hydride generation as a sample-introduction technique in atomic spectrometry: fundamentals, interferences, and applications
    Analytical and Bioanalytical Chemistry, 2007
    Co-Authors: Francisco Laborda, Eduardo Bolea, Juan R. Castillo
    Abstract:

    Electrochemical hydride generation (EC-HG) has been proposed as a valid alternative to chemical generation as a sample-introduction technique in atomic spectrometry. In this review fundamental aspects of the technique are revised, including designs of Electrolytic Cells, mechanisms of the generation process, and interferences caused by the presence of different species. Special attention is paid to the role of the configuration of the cathodes and their materials on the efficiency of hydride generation and on interferences from concomitant species. An overview of the application of EC-HG to the analysis of real samples is also given.

  • Electrochemical hydride generation as a sample-introduction technique in atomic spectrometry: fundamentals, interferences, and applications
    Analytical and Bioanalytical Chemistry, 2007
    Co-Authors: Francisco Laborda, Eduardo Bolea, Juan R. Castillo
    Abstract:

    Electrochemical hydride generation (EC-HG) has been proposed as a valid alternative to chemical generation as a sample-introduction technique in atomic spectrometry. In this review fundamental aspects of the technique are revised, including designs of Electrolytic Cells, mechanisms of the generation process, and interferences caused by the presence of different species. Special attention is paid to the role of the configuration of the cathodes and their materials on the efficiency of hydride generation and on interferences from concomitant species. An overview of the application of EC-HG to the analysis of real samples is also given.

A L Alexeionescu - One of the best experts on this subject based on the ideXlab platform.

  • current voltage characteristics and impedance spectroscopy surface conduction and adsorption desorption effects in Electrolytic Cells
    Journal of Physical Chemistry C, 2020
    Co-Authors: A L Alexeionescu, G Barbero, L R Evangelista, E K Lenzi
    Abstract:

    We present a theoretical analysis of the current–voltage characteristics of Electrolytic Cells using their electrical impedance response to a simple periodic external voltage of small amplitude. Th...

  • current voltage characteristics and impedance spectroscopy surface conduction and adsorption desorption effects in Electrolytic Cells
    The Journal of Physical Chemistry, 2020
    Co-Authors: A L Alexeionescu, G Barbero, L R Evangelista, E K Lenzi
    Abstract:

    We present a theoretical analysis of the current–voltage characteristics of Electrolytic Cells using their electrical impedance response to a simple periodic external voltage of small amplitude. The examined cell is a thin-film electrolyte (solid, liquid, or gel) sandwiched between flat electrodes at which Ohmic conduction or adsorption–desorption phenomena occur. The basic equations of the Poisson–Nernst–Planck (PNP) model are analytically solved for the case of two diffusing mobile ions (ambipolar diffusion), yielding the charge densities in thermal equilibrium and the profile of the electric potential across the sample. Proper boundary conditions permit us to explore the influence of blocking, Ohmic and adsorbing-desorbing electrodes on the final I(V) curves. Remarkable, it is possible to establish an equivalence between the Ohmic and adsorption–desorption boundary conditions for a general set of physically relevant values of the parameters characterizing the electrodes. This equivalence is a natural way to further incorporate a frequency dispersion caused by the surfaces on the whole response of the cell. This makes the approach well-tailored to investigate the role of the different diffusion coefficients for cations and anions as well as the surface effects on the voltammetry measurements in insulators containing ionic impurities.

  • role of the adsorption phenomenon on the ionic equilibrium distribution and on the transient effects in Electrolytic Cells
    Journal of Physical Chemistry B, 2006
    Co-Authors: Giovanni Barbero, Marco Scalerandi, F C M Freire, A L Alexeionescu
    Abstract:

    We analyze the influence of the adsorption of ions at the interfaces on the transient phenomena occurring in an Electrolytic cell submitted to a steplike external voltage. In the limit of small amplitude of the applied voltage, where the equation of the problem can be linearized, we obtain an analytical solution for the bulk and surface densities of ions and for the electrical potential. We also obtain, in this limit, the relaxation time for the transient phenomena.

E K Lenzi - One of the best experts on this subject based on the ideXlab platform.

  • current voltage characteristics and impedance spectroscopy surface conduction and adsorption desorption effects in Electrolytic Cells
    Journal of Physical Chemistry C, 2020
    Co-Authors: A L Alexeionescu, G Barbero, L R Evangelista, E K Lenzi
    Abstract:

    We present a theoretical analysis of the current–voltage characteristics of Electrolytic Cells using their electrical impedance response to a simple periodic external voltage of small amplitude. Th...

  • current voltage characteristics and impedance spectroscopy surface conduction and adsorption desorption effects in Electrolytic Cells
    The Journal of Physical Chemistry, 2020
    Co-Authors: A L Alexeionescu, G Barbero, L R Evangelista, E K Lenzi
    Abstract:

    We present a theoretical analysis of the current–voltage characteristics of Electrolytic Cells using their electrical impedance response to a simple periodic external voltage of small amplitude. The examined cell is a thin-film electrolyte (solid, liquid, or gel) sandwiched between flat electrodes at which Ohmic conduction or adsorption–desorption phenomena occur. The basic equations of the Poisson–Nernst–Planck (PNP) model are analytically solved for the case of two diffusing mobile ions (ambipolar diffusion), yielding the charge densities in thermal equilibrium and the profile of the electric potential across the sample. Proper boundary conditions permit us to explore the influence of blocking, Ohmic and adsorbing-desorbing electrodes on the final I(V) curves. Remarkable, it is possible to establish an equivalence between the Ohmic and adsorption–desorption boundary conditions for a general set of physically relevant values of the parameters characterizing the electrodes. This equivalence is a natural way to further incorporate a frequency dispersion caused by the surfaces on the whole response of the cell. This makes the approach well-tailored to investigate the role of the different diffusion coefficients for cations and anions as well as the surface effects on the voltammetry measurements in insulators containing ionic impurities.

  • on the equivalence between specific adsorption and kinetic equation descriptions of the admittance response in Electrolytic Cells
    Journal of Chemical Physics, 2013
    Co-Authors: L R Evangelista, Giovanni Barbero, E K Lenzi, James Ross Macdonald
    Abstract:

    The response of an Electrolytic cell, in the shape of a slab, is analyzed in the framework of the Poisson-Nernst-Planck model in the limit of full dissociation. Two different types of boundary conditions on the electrodes are compared. One type describes the exchange of charges between the volume and the external circuit, in the form originally proposed by Chang and Jaffe and later extended to include specific adsorption, where the surface current density is proportional to the variation of the surface bulk density of ions with respect to the value of equilibrium. The other one describes the surface adsorption, in the limit of Langmuir. We show that in the simple case where the ions dissolved in the insulating liquid are identical in all the aspects, except for the sign of the charge, the two models are equivalent only if the phenomenological parameter entering the boundary condition of the Chang-Jaffe model, κ, is frequency dependent, and related to the adsorption coefficient, ka, in the form κ = iωτ/(1 ...

  • fractional diffusion equation and impedance spectroscopy of Electrolytic Cells
    Journal of Physical Chemistry B, 2009
    Co-Authors: E K Lenzi, L R Evangelista, Giovanni Barbero
    Abstract:

    The influence of the ions on the electrochemical impedance of a cell is calculated in the framework of a complete model in which the fractional drift-diffusion problem is analytically solved. The resulting distribution of the electric field inside the sample is determined by solving Poisson's equation. The theoretical model to determine the electrical impedance we are proposing here is based on the fractional derivative of distributed order on the diffusion equation. We argue that this is the more convenient and physically significant approach to account for the enormous variety of the diffusive regimes in a real cell. The frequency dependence of the real and imaginary parts of the impedance are shown to be very similar to the ones experimentally obtained in a large variety of Electrolytic samples.

Giovanni Barbero - One of the best experts on this subject based on the ideXlab platform.

  • Effects of a dc bias on electrical impedance spectroscopy in Electrolytic Cells
    Journal of Molecular Liquids, 2018
    Co-Authors: Giovanni Barbero, Antonio Gliozzi, Marco Scalerandi, Antonio Maria Scarfone
    Abstract:

    Abstract Characterization of Electrolytic Cells is often inferred from measurements of their electrical properties as a function of frequency by applying a sinusoidal voltage. In some cases, a dc bias is intrinsically present in addition to the ac stimulus and its effects are often neglected although they may become relevant in certain situations. As a consequence, the interpretation of the observed results might be misleading. Our aim is to estimate the influence of the bias solving numerically the Poisson-Nernst-Planck model for an Electrolytic cell submitted to an ac external voltage superimposed to a bias. According to our analysis, even in the case of a small bias, the estimated Debye frequency and the low-frequency resistance of the cell are significantly influenced by it.

  • theoretical interpretation of warburg s impedance in unsupported Electrolytic Cells
    Physical Chemistry Chemical Physics, 2017
    Co-Authors: Giovanni Barbero
    Abstract:

    We discuss the origin of Warburg's impedance in unsupported Electrolytic Cells containing only one group of positive and one group of negative ions. Our analysis is based on the Poisson–Nernst–Planck model, where the generation-recombination phenomenon is neglected. We show that to observe Warburg-like impedance the diffusion coefficient of the positive ions has to differ from that of the negative ones, and furthermore the electrodes have to be not blocking. We assume that the non-blocking properties of the electrodes can be described by means of an Ohmic model, where the charge exchange between the cell and the external circuit is described by means of an electrode conductivity. For simplicity we consider a symmetric cell. However, our analysis can be easily generalized to more complicated situations, where the cell is not symmetric and the charge exchange is described by the Chang–Jaffe model, or by a linearized version of the Butler–Volmer equation. Our analysis allows justification of the expression for Warburg's impedance proposed previously by several groups, based on wrong assumptions.

  • reanalysis of the electrode polarization in Electrolytic Cells limited by blocking electrodes
    Physical Review E, 2016
    Co-Authors: Ross J Macdonald, Giovanni Barbero
    Abstract:

    We evaluate the effect of ions on the electric response of an insulting liquid by means of the total electric polarization induced in a cell by an external field. The limiting surfaces are assumed blocking and identical and the ions pointike nonpolarizable charged particles. The analysis is limited to the case where the selective ionic adsorption is absent, in such a manner that in the absence of external electric field the sample is locally and globally neutral. We obtain formulas for the effective dielectric constant renormalized by the presence of the ions in the absence and presence of adsorption from the surfaces. Our results coincide with those obtained by means of the electric impedance of the cell. From the coincidence of the results relevant to the effective dielectric constant we infer that the ions in an insulating liquid do not have a conductive or dielectric nature. They are just electric charges dissolved in an insulating liquid.

  • Comment on "Modeling of electrode polarization for Electrolytic Cells with a limited ionic adsorption"
    Physical Review E, 2014
    Co-Authors: A.l. Alexe-ionescu, Giovanni Barbero, Ioannis Lelidis
    Abstract:

    Recently, Sawada [Phys. Rev. E 88, 032406 (2013)] proposed a model to take into account the dielectric dispersion of ionic origin in a weak electrolyte cell. We first show that the model is based on questionable assumptions. Next, we point out an error in the author's calculation of the current in the external circuit. Finally, we demonstrate why some criticism on recent papers is irrelevant

  • on the equivalence between specific adsorption and kinetic equation descriptions of the admittance response in Electrolytic Cells
    Journal of Chemical Physics, 2013
    Co-Authors: L R Evangelista, Giovanni Barbero, E K Lenzi, James Ross Macdonald
    Abstract:

    The response of an Electrolytic cell, in the shape of a slab, is analyzed in the framework of the Poisson-Nernst-Planck model in the limit of full dissociation. Two different types of boundary conditions on the electrodes are compared. One type describes the exchange of charges between the volume and the external circuit, in the form originally proposed by Chang and Jaffe and later extended to include specific adsorption, where the surface current density is proportional to the variation of the surface bulk density of ions with respect to the value of equilibrium. The other one describes the surface adsorption, in the limit of Langmuir. We show that in the simple case where the ions dissolved in the insulating liquid are identical in all the aspects, except for the sign of the charge, the two models are equivalent only if the phenomenological parameter entering the boundary condition of the Chang-Jaffe model, κ, is frequency dependent, and related to the adsorption coefficient, ka, in the form κ = iωτ/(1 ...

L R Evangelista - One of the best experts on this subject based on the ideXlab platform.

  • current voltage characteristics and impedance spectroscopy surface conduction and adsorption desorption effects in Electrolytic Cells
    Journal of Physical Chemistry C, 2020
    Co-Authors: A L Alexeionescu, G Barbero, L R Evangelista, E K Lenzi
    Abstract:

    We present a theoretical analysis of the current–voltage characteristics of Electrolytic Cells using their electrical impedance response to a simple periodic external voltage of small amplitude. Th...

  • Electric response of asymmetric Electrolytic Cells to small AC signals
    Journal of Electroanalytical Chemistry, 2020
    Co-Authors: A.l. Alexe-ionescu, G Barbero, L R Evangelista
    Abstract:

    Abstract We present an extended theory for the electric response of an Electrolytic cell with two different electrodes to a small amplitude external ac stimulus. In this case, the two electrodes limiting the cell are different in the sense that the spatial dependencies of the dynamical quantities characterising the system have not a well defined symmetry, with respect to the electrodes. This requires extending the Poisson-Nernst-Planck model to solve the fundamental equations allowing for the analytical determination of the electric impedance of the cell. The new theoretical framework opens the pathway to describe asymmetric Electrolytic Cells limited by conductive or adsorbing-desorbing boundaries.

  • current voltage characteristics and impedance spectroscopy surface conduction and adsorption desorption effects in Electrolytic Cells
    The Journal of Physical Chemistry, 2020
    Co-Authors: A L Alexeionescu, G Barbero, L R Evangelista, E K Lenzi
    Abstract:

    We present a theoretical analysis of the current–voltage characteristics of Electrolytic Cells using their electrical impedance response to a simple periodic external voltage of small amplitude. The examined cell is a thin-film electrolyte (solid, liquid, or gel) sandwiched between flat electrodes at which Ohmic conduction or adsorption–desorption phenomena occur. The basic equations of the Poisson–Nernst–Planck (PNP) model are analytically solved for the case of two diffusing mobile ions (ambipolar diffusion), yielding the charge densities in thermal equilibrium and the profile of the electric potential across the sample. Proper boundary conditions permit us to explore the influence of blocking, Ohmic and adsorbing-desorbing electrodes on the final I(V) curves. Remarkable, it is possible to establish an equivalence between the Ohmic and adsorption–desorption boundary conditions for a general set of physically relevant values of the parameters characterizing the electrodes. This equivalence is a natural way to further incorporate a frequency dispersion caused by the surfaces on the whole response of the cell. This makes the approach well-tailored to investigate the role of the different diffusion coefficients for cations and anions as well as the surface effects on the voltammetry measurements in insulators containing ionic impurities.

  • on the equivalence between specific adsorption and kinetic equation descriptions of the admittance response in Electrolytic Cells
    Journal of Chemical Physics, 2013
    Co-Authors: L R Evangelista, Giovanni Barbero, E K Lenzi, James Ross Macdonald
    Abstract:

    The response of an Electrolytic cell, in the shape of a slab, is analyzed in the framework of the Poisson-Nernst-Planck model in the limit of full dissociation. Two different types of boundary conditions on the electrodes are compared. One type describes the exchange of charges between the volume and the external circuit, in the form originally proposed by Chang and Jaffe and later extended to include specific adsorption, where the surface current density is proportional to the variation of the surface bulk density of ions with respect to the value of equilibrium. The other one describes the surface adsorption, in the limit of Langmuir. We show that in the simple case where the ions dissolved in the insulating liquid are identical in all the aspects, except for the sign of the charge, the two models are equivalent only if the phenomenological parameter entering the boundary condition of the Chang-Jaffe model, κ, is frequency dependent, and related to the adsorption coefficient, ka, in the form κ = iωτ/(1 ...

  • fractional diffusion equation and impedance spectroscopy of Electrolytic Cells
    Journal of Physical Chemistry B, 2009
    Co-Authors: E K Lenzi, L R Evangelista, Giovanni Barbero
    Abstract:

    The influence of the ions on the electrochemical impedance of a cell is calculated in the framework of a complete model in which the fractional drift-diffusion problem is analytically solved. The resulting distribution of the electric field inside the sample is determined by solving Poisson's equation. The theoretical model to determine the electrical impedance we are proposing here is based on the fractional derivative of distributed order on the diffusion equation. We argue that this is the more convenient and physically significant approach to account for the enormous variety of the diffusive regimes in a real cell. The frequency dependence of the real and imaginary parts of the impedance are shown to be very similar to the ones experimentally obtained in a large variety of Electrolytic samples.