Ionic Migration Effects Research Articles

Charge transport in mixed metal halide perovskite semiconductors.

Investigation of the inherent field-driven charge transport behaviour of three-dimensional lead halide perovskites has largely remained challenging, owing to undesirable ionic migration effects near room temperature and dipolar disorder instabilities prevalent specifically in methylammonium-and-lead-based high-performing three-dimensional perovskite compositions. Here, we address both these challenges and demonstrate that field-effect transistors based on methylammonium-free, mixed metal (Pb/Sn) perovskite compositions do not suffer from ion migration effects as notably as their pure-Pb counterparts and reliably exhibit hysteresis-free p-type transport with a mobility reaching 5.4 cm2 V-1 s-1. The reduced ion migration is visualized through photoluminescence microscopy under bias and is manifested as an activated temperature dependence of the field-effect mobility with a low activation energy (~48 meV) consistent with the presence of the shallow defects present in these materials. An understanding of the long-range electronic charge transport in these inherently doped mixed metal halide perovskites will contribute immensely towards high-performance optoelectronic devices.

Understanding lead iodide perovskite hysteresis and degradation causes by extensive electrical characterization

We studied the hysteresis and electric field effects on planar CH3NH3PbI3 perovskite devices, synthetized from laser-ablated precursors, by means of electrical characterizations at different scan rates and optical measurements. The aim of our investigation is to characterize the phenomena behind perovskite degradation under prolonged applied electric field. Using a perovskite more resistant to electric field induced degradation, we run long time characterizations that were not accomplishable before. Thus, we distinguished all the degradation-involved phenomena. The results point to the presence of ions migrating in the perovskite when the device is biased. Our data showed that ion migration degrades the interfaces with the consequent creation of degradation layers that limit the current injected in the device and the extracted photocurrent. These layers where detected also by means of optical Raman characterization. In order to explain the details of the mechanisms concurring to the observed behaviors, we presented a qualitative model.The observed phenomena exacerbated by the planar structure are even more destructive on standard solution processed perovskites to which the results of this work can be extended. Since, the same degradation dynamics occur on vertical devices, typical on perovskite solar cells, this work provides a useful in-depth analysis of the ionic migration effects.

Effect of migration on homogeneous redox electrocatalysis at rotating disk electrode

This work is devoted to the theoretical study of the effect of migration on homogeneous redox electrocatalysis of electrochemical reactions at the rotating disk electrode. The mathematical model involves the Nernst-Planck equations that take into account diffusion, migration, convection, homogeneous chemical reactions, and electroneutrality condition. For the convenience of solving and analyzing the results, the mathematical model was reduced to the dimensionless form. The numerical solution was performed by the finite volume method on the nonuniform grid. Based on the results of computational experiments, for the electrocatalytic reduction of hydrogen peroxide in the presence of ferric ions, three zones were observed in the plane of concentrations of H2O2–H2SO4. These zones differ in the nature of the limiting current: for H+ ions, Fe+2 ions, and hydrogen peroxide H2O2. The dependences of the limiting current on the concentrations of H2SO4 and H2O2 were determined with and without consideration of the ionic migration. It was found that the ionic migration may be ignored only in the cases that the concentration of H2SO4 is significantly higher than that of H2O2. It was shown that the strongest effect of ionic migration is reached on the boundaries between zones that differ in the nature of the limiting current.

Antistatic effects and mechanism of ionic liquids for methyl vinyl silicone rubber

ABSTRACTThe effect of two ionic liquids (ILs), namely, 1‐allyl‐3‐methyl imidazolium chloride ([AMIM]Cl) and 1‐ethyl‐3‐methyl imidazolium tetrafluoroborate ([EMIM]BF4), on the surface and volume resistivities, mechanical properties, transparency, and water contact angle of methyl vinyl silicone rubber (MVQ) were investigated. The chemical structures of the two ILs before and after heat treatment were characterized by Fourier transform infrared spectroscopy. The morphology and fluorine and chlorine elemental dispersion were characterized by field emission scanning electron microscopy and energy‐dispersive X‐ray spectroscopy mapping, respectively. The antistatic mechanism was revealed. The results show that the MVQ–[EMIM]BF4 composites had lower surface and volume resistivities than the MVQ–[AMIM]Cl composites. The mechanical properties of the MVQ–[EMIM]BF4 and MVQ–[AMIM]Cl composites were slightly lower than those of the pristine MVQ. With increasing [EMIM]BF4 content, the surface and volume resistivities and water contact angle of the MVQ–[EMIM]BF4 composites decreased. When the content of [EMIM]BF4 was 2.0 phr, the MVQ–[EMIM]BF4 composites showed better antistatic performance with lower surface and volume resistivities of 9.6 × 109 Ω and 1.2 × 1011 Ω cm, respectively. The antistatic mechanism of the MVQ–IL composites was ascribed to the synergistic effect of ionic migration and moisture absorption. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45180.

Ionic migration effects on the mechanical properties of glass surfaces

Modifications of glass surfaces were produced by the ionic migration of alkaline ions due to an external electric field. Using aluminum plates as electrodes, hydrogen ions penetrate into samples substituting for alkaline ions. With deposited silver films as the positive electrode, Ag + ions penetrate into the glass substituting for Na + ions in the depleted region. The hardness and residual stresses at glass surface produced by the ionic migration are measured. Hardness was measured using the nanoindentation technique. The surface stress generated by the penetration of foreign ions was measured using the indentation cracks lengths generated by a Vickers indentation. We observed that presence of an internal hydrogen layer produces a tensile residual stress at the sample surface. A compressive stress was observed as a result of a Ag + ions layer near the anode region. The measured stresses are compared with the stresses calculated using a model which considers the existence of a layer of foreign ions with different ionic radii at the glass surface.

The Dynamics of Morphological Instability during Electrodeposition

Mullins‐Sekerka morphological stability theory is applied to analyze the possible factors affecting the evolution of roughness and protrusions. The analysis introduces, for the first time, a damping factor which determines whether the diffusion layer thickness is affected by the surface perturbations. The results show that increasing the reacting‐ion concentration and concentration gradient at the electrode‐solution interface and decreasing the diffusion layer thickness and surface concentration favor morphological instability. The effect of ionic migration within the diffusion layer is also considered. The analysis indicates that the concentration gradient at the interface is the main deposition parameter controlling the morphology of the deposit. In the extreme case, when the diffusion layer thickness is smaller than the wavelength of the surface perturbation, the diffusion layer follows the perturbed surface, and the electrodeposition becomes stable.

A mathematical model of pulse plating on a rotating disk electrode

AbstractA galvanostatic pulse plating model is presented for the electrodeposition of an alloy on a rotating disk electrode. This model is used to simulate the electrodeposition of nickel/chrome alloys. The mass transport equations used in the model include the effects of diffusion, migration and convection; and the electrode kinetics are described by the Butler‐Volmer equation. It is predicted that the effect of ionic migration is significant and therefore should be included in models of pulse plating.

GENERAL LINEARIZED MATRIX THEORY OF ELECTROCHEMICAL MASS TRANSFER WITH APPLICATIONS TO ELECTRODE PROCESSES AND ION EXCHANGE

Abstract A general linearized matrix theory for electrochemical mass transfer is presented. The accuracy of the theory when applied to cases where electric current exists is tested by comparing results with exact calculations of the effect of ionic migration on limiting currents at a rotating disk electrode with laminar flow and at a flat plate electrode adjacent to a stagnant fluid film. Application of the theory is further illustrated by using it to calculate the effect of ionic migration on limiting currents in a turbulent, law-of-the-wall boundary layer. Finally, the theory is used to evaluate commonly used “film-model” methods for generalizing binary mass-transfer correlations to multicomponent nonideal mixtures. For this last purpose, a film-model generalization method was developed for nonideal electrolyte mixtures. The method is equivalent to that used by Krishnamurthy and Taylor (1985) for mass-transfer in nonideal nonelectrolyte mixtures. Results using the film-model method are compared to matri...

A Mathematical Model for the Electrodeposition of Alloys on a Rotating Disk Electrode

A general multiple electrode reaction model for electrodeposition of alloys on a rotating disk electrode is presented. Included in the model are mass transport equations with the effect of ionic migration, Butler‐Volmer kinetic rate expressions, and the mole fractions of the individual components in the solid state. The model shows that the effect of ionic migration is important and that plating variables such as applied potential, pH, and bulk concentration can be included. Two examples (Ni‐P and Ru‐Ni‐P) are used to illustrate the predictions of the model.

Modelling of a continuous parallel plate plug flow electrochemical reactor: electrowinning of copper

On the basis of copper winning in a sulphuric acid medium this paper presents an original calculation method for the design of a continuous parallel plate electrolytic cell consisting of three zones: a turbulent bulk in which convection and migration take place and two thin boundary layers at each electrode where diffusion and migration phenomena are taken into account. Current densities and species concentration profiles may be deduced from this model with the aid of mass transfer and electrochemical kinetic data. For conditions corresponding to industrial applications it can be shown that longitudinal migration in the bulk can be neglected. The validity of the model is successfully proved; in particular, results accounting for the effect of ionic migration on the limiting current density are in a good agreement with previous studies.

The film model for determining the effect of ionic migration in electrochemical systems

The film model is used to examine the effect of ionic migration on the concentration of ionic species and on the electrolyte potential profiles inside the Nernst layer.

Effect of Ionic Migration on Absorption Rate of CO<SUB>2</SUB> into NaOH Solutions

Effect of Ionic Migration on Absorption Rate of CO<SUB>2</SUB> into NaOH Solutions

A Model of the Bromine/Bromide Electrode Reaction at a Rotating Disk Electrode

A mathematical model is presented for the electrode reaction at a rotating disk electrode. The model includes current density‐overpotential expressions for the electrode reaction according to either the Volmer‐Heyrovsky (V‐H) or the Volmer‐Tafel (V‐T) mechanism and the transport equations including the effect of ionic migration. The model is used to predict current‐overpotential curves for various cases of interest. Qualitative comparison of the model predictions to literature data shows that either the V‐H or the V‐T mechanism, with V controlling, may be acceptable for the reaction.

Effect of electric fields on the thermal decomposition of calcium carbonate

The thermal decomposition of CaCO 3 powder and single crystal samples to CaO has been shown by X-ray diffraction and ESCA to be assisted by the application of external DC electric fields during the reaction. The effect is particularly marked at the positive electrode. The results are discussed in terms of both ionic migration effects and the field-induced electro-adsorption/electro-desorption of gaseous CO 2 at the surface of a semiconductor. Approximate calculations based on both theories show that ionic migration cannot account for the magnitude of the observed effects, but a reasonably satisfactory explanation is provided by the application of semi-conductor surface theory to the system.

Negative ionic cross diffusion coefficients in electrolytic solutions

All existing experimental examples of oscillating homogeneous chemical reactions and dissipative structures involve ionic systems. The linear stability analysis is applied to electrolytic solutions by including diffusion potential and ionic migration effects. It is shown that negative off-diagonal diffusion coefficients can exist in electrolytic solutions, since ions diffuse interactively even in dilute solutions and are influenced by the resulting diffusion potential. The inclusion of negative off-diagonal diffusion co-efficients can increase the possibility of oscillations and spatial structures.

The effects of ionic migration on oscillations and pattern formation in chemical systems

The possible emergence of oscillations and patterns due to coupling between transformation and transport processes is applied to electrolytic solution subjected to an applied electric field. The stability analysis is broadened in order to include ionic migration effects. Analysis of a simple example of two ionic species undergoing chemical reactions, diffusion and migration shows that even in such simple systems there are certain conditions under which spontaneous oscillations and dissipative structures might develop.

The Role of Bisulfate Ions in Ionic Migration Effects

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Role of Bisulfate Ions in Ionic Migration EffectsLimin Hsueh and John NewmanCite this: Ind. Eng. Chem. Fundamen. 1971, 10, 4, 615–620Publication Date (Print):November 1, 1971Publication History Published online1 May 2002Published inissue 1 November 1971https://doi.org/10.1021/i160040a013RIGHTS & PERMISSIONSArticle Views128Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts

Free‐Convection Mass Transfer with a Supporting Electrolyte

Free convection and ionic migration effects are reviewed. Electrolytic free convection is treated theoretically for solutions and for solutions without added electrolyte and with additions of or . The effect of ionic migration on limiting currents is investigated. The presence of supporting electrolyte lowers the electric field, as in stagnant or forced convective systems. In addition, the concentration distributions of added electrolytes affect the density distribution, hence, the velocity profile in free convection, and, indirectly, the value of the calculated limiting currents.

Effect of Ionic Migration on Limiting Currents

Effect of Ionic Migration on Limiting Currents

The motion of liquid alloy zones along a bar under the influence of an electric current

Abstract A critical examination is made of the interpretation of experiments reported by Pfann et al. (1957) in which molten alloy zones were observed to move along the surface of a germanium bar through which a current was passed. It is shown that the influence of the Peltier effect along cannot account for all of their experimental results and an alternative interpretation is proposed in which the motion is ascribed to a combination of the Peltier effect and ionic migration in the molten alloy. A theory is presented which yields an expression for the steady velocity of a thin zone under the influence of a temperature gradient, Peltier, Thomson and ionic migration effects. Certain special cases are considered and a new method of measuring differential ionic mobility is proposed.