Electrochemical Thermodynamics Research Articles

Separation of Double-Layer Charging and Faradaic Processes at Electrodes

In studying transient electrode processes in aqueous solutions, the current density is often expressed in terms of separate capacitive charging and faradaic contributions, in = C(∂η/∂t) + if without a critical evaluation of the underlying assumptions. This paper investigates rigorously the basic concepts and assumptions involved in justifying the use of this equation, starting from the basic principles of electrochemical thermodynamics, kinetics, and mass transfer. The equation derives from a species mass balance for the electrochemical interface, which justifies already an a priori separation of the double layer and faradaic charges. An important assumption required in further analysis to obtain this equation is to neglect time dependent variations in the concentrations of species, which take part in the electrode reaction, adjacent to the electrode surface in the solution. It is further necessary to neglect variations in the conductivity with position near the electrode and assume small concentrations of the species taking part in the electrode reaction.

Phase transition in porous electrodes

It is shown by Monte Carlo simulation that electrochemical thermodynamics of electrolytes in a porous electrode is qualitatively different from that in the bulk with a planar electrode. In particular, first order phase transitions occur in porous electrodes when the pore size is comparable to the ion size of the electrolytes: as the voltage is increased from zero, the surface charge density and the ion density in the porous electrodes discontinuously change at a specific voltage. The critical points for those phase transitions are identified.

Preface

The electrochemical community in the southeastern part of Europe has been renowned worldwide for more than 50 years. The contributions to electrochemical science, involving publications, scientific meetings, or, generally speaking, electrochemical research, development, education, and applications are recognized to a wider extent than expected, bearing in mind this relatively small geographic area. The tradition connected with 16 biannual Yugoslav Symposia on Electrochemistry, followed by a few Croatian Electrochemical Symposia and Electrochemical Symposia of Serbia and Montenegro merged into a Regional Symposium. Actually, the mutual idea was born in Belgrade, Serbia and Zagreb, Croatia. Going toward the European Union, nine chemical societies from southeast European organized the 2nd Symposium (the Serbian Chemical Society was the local organizer), held in Belgrade, Serbia, 6-10 June 2010 http://www.rse-see.net. The 1st Symposium, with the Croatian Society of Chemical Engineers as the local organizer, was held in Rovinj, Croatia in 2008.The 2nd Symposium was attended by more than 200 participants, including young scientists (such as university students participating in the Satellite Student Symposium with 19 contributions) from more than 30 countries. Eminent invited plenary and keynote speakers delivered 9 and 18 lectures, respectively, and 46 oral and 118 poster presentations were contributed, promoting thereby contemporary electrochemical knowledge even outside the region. Topics such as fundamental aspects of electrochemistry, energy conversion, materials, corrosion, environmental electrochemistry, and bio-electrochemistry, among others, lead to the conclusion that this was a very successful meeting.The selected papers published herein give a representative view of the Symposium, considering electrochemical thermodynamics, the fundamentals of electrochemical kinetics, the structure of electrode materials, and some basic electrochemical reactions and applications of electrochemical and materials science principles as biomedical implants, in analytical chemistry and corrosion.The 3rd Regional Symposium on Electrochemistry of Southeast Europe is scheduled for 2012. The local organizer is the Romanian Chemical Society, and the venue will be Bucharest, Romania.Branislav NikolićConference Editor

What Are Batteries, Fuel Cells, and Supercapacitors?

AbstractFor Abstract see ChemInform Abstract in Full Text.

What Are Batteries, Fuel Cells, and Supercapacitors?

Electrochemical energy conversion devices are pervasive in our daily lives. Batteries, fuel cells and supercapacitors belong to the same family of energy conversion devices. They are all based on the fundamentals of electrochemical thermodynamics and kinetics. All three are needed to service the wide energy requirements of various devices and systems. Neither batteries, fuel cells nor electrochemical capacitors, by themselves, can serve all applications.

The precursor of the International Society of Electrochemistry

The International Committee of Electrochemical Thermodynamics and Kinetics (French acronym, C.I.T.C.E.) was the precursor of the International Society of Electrochemistry. This committee was founded in 1949 by Pourbaix with the collaboration of Van Rysselberghe and several European electrochemists. The circumstances and participants at the beginning are evoked as well as some of the activities and the subsequent evolution.

From CITCE to ISE

In September 1970 the change of name from CITCE to ISE was voted by the members. A total of 495 ballots had been sent out, 308 had been returned. A total of 269 members were favorable to the change, 37 opposed, and two ballots were blank. One year later the new statutes were accepted by a large majority. These votes marked a turning-point in the history of our Society. In the beginning, CITCE was essentially a European association. As the name says, it was even mainly French speaking: CITCE (Comite International de Thermodynamique et de Cinetique Electrochimiques). The founders of CITCE and first members were frenchspeaking or could express themselves in French: Professors M. Pourbaix, G. Valensi, P. van Rysselberghe, N. Ibl, T.P. Hoar, to name only a few of them. As the name ‘International Committee of Electrochemical Thermodynamics and Kinetics’ says, the new association was meant to be more than just a scientific society with its traditional activities: CITCE should have been an international body collecting and publishing electrochemical data, being presented as references and standards. However, very soon the yearly meetings with their presentations of scientific papers and their publication in Electrochimica Acta since 1956 became the main activities of CITCE. CITCE grew very rapidly. There have been several reasons for its fast development: first, the situation of electrochemistry in the 1950s. As Klaus Vetter pointed out in 1960 in the preface to his book ‘Elektrochemische Kinetik’, until the midst of this century electrochemistry was considered and taught as part of thermodynamics. Electrochemical kinetics were just mentioned in the textbooks, without any systematic treatment. It was in the years following the foundation of CITCE, that electrochemical kinetics developed and were a subject worked on by a large number of scientists. At the same time, industrial applications of electrochemistry spread widely: we will just mention that fuel-cells started to be developed at that time. Hence, there was a great need for publication, discussion and exchange in the field of electrochemistry. But there have been also other important reasons favoring the development of CITCE. After the second world-war, there was no scientific society in Europe dealing mainly with electrochemistry. CITCE filled this gap. Finally, there was the political situation in Europe, divided into ‘western’ and ‘eastern’ countries. CITCE with its french-speaking aspect, politically absolutely neutral, was acceptable as a scientific society and platform for exchange by the communistic countries. As electrochemistry in the Soviet Union, Czechoslovakia, Hungary and other eastern countries was very strong, CITCE was an ideal place for scientific exchange between east and west. All these factors which determined the development of CITCE played their role in the process of changing the name to ISE as well. In the 60s the activities of CITCE became really worldwide. The 14th meeting was held in 1963 in Moscow. The society represented 35 contries and had 421 members. 1966 CITCE met in Japan and represented 36 countries with 539 members. In 1968 the 19th Meeting was held in Detroit. CITCE counted 638 members from 34 countries. It was evident, that in these meetings English became the leading language. As in 1965 the term of presidency had been limited to 1 year (fixed to 2 years from 1971 on), the influence of the founders on the Board and the use of French declined. It was at the Detroit meeting that the idea to change the name of CITCE to ISE and to adopt new statutes was discussed for the first time on the Board. The opinions were divided. On the one hand, practically everybody agreed, that CITCE had developped into a true international scientific society. On the other, it was questioned if this development needed really to be followed by a change of name. Indeed, CITCE was known as CITCE, even when younger members did not exactly know anymore what that acronym meant. Changing the name seemed to be a loss of tradition, or even more, a loss of identity. If this point of view was naturally defended by the founders and older members, it was also considered by the representatives of the eastem countries. They were afraid, that these changes Written in 1999.

The Electrochemical Thermodynamics for Chemical Reactions in Dispersed Cells

There is a large specific surface area in a dispersed cell, so much so that there are some notable differences in thermodynamic quantities for a chemical reaction in the cell because of the strong surface effect. The thermodynamic relations between the electromotive force (emf) and the dispersity of a cell and between each of thermodynamic properties and the dispersivity of the cell are derived, and the effects of degree of dispersion of substances in the cell on the emf and the thermodynamic properties are discussed. The results show that the emf, the equilibrium constant, the entropy for reaction, the heat of reaction, and the enthalpy of reaction vary with the dispersivities of the reactants or/and the products in the cell. And two new concepts, surface emf and dispersion cell, are put forward in this paper.

Corrosion and electrochemistry of zinc

Properties, Products, and Processes. Electrochemical Thermodynamics and Elemental Reactions. Passivation and Surface Film Formation. Semiconductor Electrochemistry of Zinc Oxide. Corrosion Potential and Corrosion Current. Corrosion Products. Corrosion Forms. Atmospheric Corrosion. Corrosion in Water and Aqueous Solutions. Corrosion in Soil. Under Paint Corrosion. Zinc Rich Coating. Corrosion in Concrete. Corrosion in Batteries. Corrosion in other Environments. Index.

Thermodynamical analysis of non-stoichiometric thallium oxides and reactivity prediction for electrosynthesis

An approach is proposed for the simulation of potential-pH diagrams which takes into account deviations of oxide composition from stoichiometry. The model of regular solid solution is used for the analysis of electrochemical thermodynamics of thallous ion (oxide)-thallic oxide-thallium Superoxide (peroxide) system. Potential values corresponding to certain compositions of the product of Tl 2O 3 anodic oxidation are predicted.

Thermodynamics and corrosion

After having paid tribute to the pioneer works of Fritz Haber, Walther Nernst, Ulick Evans and Carl Wagner, the author mentions the joint activities of CITCE and CEBELCOR in electrochemistry and corrosion, with special reference to graphical methods in electrochemical thermodynamics (electrode potential/pH and electrode potential/temperature diagrams) and in electrochemical kinetics (polarization curves in stirred solution). Examples of results obtained by these methods are given concerning corrosion and some other fields related to electrochemistry. The author expresses the wish that further work be conducted in these areas, preferably by a group of eletrochemists and other scientists who would accept to link their efforts in ‘applied thermodynamics and corrosion’ according to a ‘moral charter’ similar to the one which led in 1949, in electrochemistry, to the creation of CITCE.

Chemical and mechanical properties of redox polymer-modified electrodes: Part I. A mechanical/electrochemical model

A model is developed to describe the coupling of the mechanical and electrochemical thermodynamics of redox polymer film conversion for systems in which there is a net change in the charge per redox site associated with this redox conversion. The electrostatically forced intrusion of compensating charge, in the form of ions of the supporting electrolyte, into the polymer film is predicted to result in non-Nernstian behavior because of the finite void volume within the film and the finite molar volume of the charge-compensating ion. The physical consequences of this phenomenon are the forced swelling of the polymer film, a process which in the presence of crosslinks (either covalent or ionic) requires energy input in excess of that needed to carry out the simple electron transfer to/from the redox sites. This energy is consumed in doing work against the elastic framework of the crosslinked polymer matrix, and when couched in terms of an elastic deformation, may be considered reversible in the thermodynamic sense. The model developed here treats only the simplest of such mechanical coupling in that reversible, isotropic stress-strain is proposed to account for the non-Nernstian thermodynamics of these redox polymer films.

Electro-Analytical Techniques

This book has been written to become a bench book used in the laboratory. The Electro analytical Methods addresses chemists and biochemists that are interested in using electroanalytical techniques to supplement spectroscopic and perhaps theoretical calculations. It also addresses biologists, environmental and material scientists, physicists, medical scientists, and, most importantly, students in all branches of science, who are confronted with the need to apply electroanalytical techniques. In the short first part of the book, entitled Basic Electrochemistry, the essentials of electrochemical thermodynamics and kinetics are given. The second part, entitled Electro analytical Techniques, contains the most frequently utilized techniques, i.e., cyclic voltammetry, pulse and square-wave voltammetry, chronocoulometry, etc. The third part is devoted to electrodes and electrolytes, which are the major constituents of an electrochemical cell. Throughout the book, special attention is given to guide the user to successful laboratory experiments and a sound data evaluation.

Electrochemical corrosion of metallic biomaterials

Methods of electrochemical thermodynamics (electrode potential-pH equilibrium diagrams) and electrochemical kinetics (polarization curves) may help to understand and predict the corrosion behaviour of metals and alloys in the presence of body fluids. A short review of the literature is given concerning some applications of such methods, both in vitro and in vivo, relating to surgical implants (stainless steels, chromium-cobalt-molybdenum alloys, titanium and titanium alloys) and to dental alloys (silver-tin-copper amalgams, silver-base and gold-base casting alloys, nickel-base casting alloys). Attention is drawn to the necessity of more basic research on crevice- and fretting-corrosion of surgical implant materials and dental alloys, and to the toxicity of corrosion products. A perfect understanding of the exact significance of electrode-potentials is essential for the success of such a task

Photopotential probe of space charge and field profiles at electrolyte/silver halide interfaces: Part I. Combined electrochemical thermodynamic, adsorption and solid state vacuum interface models

A unified model for charge, field and potential distributions at silver halide/solution interfaces is developed by combining electrochemical thermodynamics with general and specific ion adsorption models. Important aspects include equality of electrochemical potential across the interface, dopant dependent internal specific adsorption of Ag i + or Ag v − as ionic surface states and specific adsorption of ions from the electrolyte. These two sources of surface charge combine to cancel or reinforce each other such that there is potential continuity between phases to provide Nernstian response. This picture allows oppositely doped silver halide electrodes to have the same interfacial potential difference while having quite different fields at the inner crystal surface. These field differences explain the diversity of photopotential effects observed.

Electroanalytical Chemistry of Membranes

I. PERSPECTIVE ON THE ROLES OF MEMBRANE ELECTROCHEMISTRY AND ELECTROANALYTICAL CHEMISTRY The thrust of electrochemistry in the past 25 years has been the study of electrode processes at blocked and unblocked electrodes, primarily metal/electrolyte interfaces. The vast literature which has been contributed by both physical and analytical chemists comprises a topic now known as electrodics to distinguish it from the more classical topics – electrochemical thermodynamics (the study of equilibrium and transport properties of electrochemical cells) and ionics (the study of equilibrium and transport properties of electrolyte solutions) – which occupied a significant number of chemists during the first 50 years of this century. Analytical electrochemists have found their interests expanding as they turn from analytical methodology to fundamental and applied studies within electrodics. Many practical contributions have been made in new and improved battery systems, fuel cells, electrochemical synthesis, electroly...

Applications of electrochemistry in corrosion science and in practice

In an introduction, a statement is made on the influence of electrochemistry during the last 30 or 40 y on corrosion research and technology, with reference to opinions expressed by U. R. Evans, R. Piontelli and C. Edeleanu. A section on Fundamentals and Electrochemical Testing Methods describes the action of CITCE in developing electrochemical thermodynamics and kinetics, and their applications. It mentions the pioneer work of C. Wagner and W. Traud and the statement of F. L. LaQue on the links connecting electrochemical research and corrosion research. The author recalls the statement of M. G. Fontana on the relative practical usefulness of corrosion education and corrosion research. The practical usefulness of three series of electrochemical methods is emphasized: the polarization resistance methods, the anodic and cathodic polarization methods, and the zero-current electrode potential measurements. A third section reviews some of the most important applications of electrochemistry in anticorrosion practice. The following topics are examined: Cathodic protection Historical Hydrogen embrittlement of pipe-lines; bi-adhesive wrapping material Cathodic protection by perfect passivation: general. Protection of carbon steels in solutions containing chloride. Protection of cast iron drying cylinders in the paper industry. Protection of stainless steels in chloride containing environments. Protection of copper in the presence of waters. Protection of aluminium in sea-water Sacrificial anodes Corrodible anodes for impressed currents Non-corrodible anodes for impressed currents Anodic protection Inhibitors: general. Water treatment. Engine coolants for automobiles. Passivation of galvanized iron. Vapour-phase inhibitors Protection of metals Iron and carbon steels: electrolysis of water. Boilers. Reinforcing bars and steel pipes embedded in concrete Weathering steels Titanium Developments of alloys: general. Titanium-palladium alloys. Copper-nickel alloys. Alloys for surgical implants Chemical surface treatments: prepassivation of brasses for heat-exchangers. Thermochemical protection of stainless steels and of refractory alloys Protective coatings: general. Wash-primers and other phosphate coatings on steel. Zinc-rich paints. Benzotriazole coatings. Rust-transformers. Electroplating. Anodized aluminium Design and miscellaneous High-temperature corrosion: fused salts. Solid electrolytes. In his conclusions, the author pays tribute to those to whom we are indebted for what is now corrosion science, and to those who have put this science into practice. He expresses opinions on the future of corrosion research. However, he agrees with M. G. Fontana in believing that what is presently most needed in the struggle against corrosion is not so much research as teaching, education and common sense.

Some aspects of electrochemical thermodynamics and equilibrium diagrams for aqueous systems at elevated temperatures and for simple molten salt systems

This paper describes briefly an approach to the electrochemical thermodynamics of corrosion, mass-transport, and deposition processes in nuclear power-plant working on the water-cycle and in homogenous molten-salt reactors. Diagrams are introduced, based on the parameter pe = (RTF −1In 10) −1. T ϵ instead of the usual redox potential, T ϵ, that are useful for illustrating equilibrium data for aqueous systems at elevated temperatures (above 100°C) and for molten salts.

Differential Thermal Analysis of Electrode Reactions

SUMMARYThe current interest in the kinetics of electrode processes was historically preceded by a consideration of electrochemical thermodynamics. The thermodynamic experiments consisted of the equilibrium (zero current) measurement of cell potentials as a function of temperature. Measurements were also made of the temperature changes associated with the charging and discharging of cells.

Intensiostatic and potentiostatic methods. Their use to predetermine the circumstances for corrosion or non-corrosion of metals and alloys

The development of intensiostatic, potentiostatic, and potentiokinetic methods of study are reported, with particular reference to the work of Evans and Wagner in applying the fundamental theories of these methods to the two principles of electrochemical thermodynamics. We describe briefly the experimental equipment used to develop these methods, emphasizing the interest presented by the thermodynamic interpretation of the potential-current polarization curves determined during electrolysis in stirred solutions. We report results obtained which concern the study of the circumstances of corrosion and noncorrosion of different metals and alloys: iron and mild steels, stainless steels, copper, aluminium and aluminium alloys. The great advances to come from these methods as research tools and as tests for corrosion estimation are noted, while indicating some causes of error and means to avoid them. We make some recommendations concerning the manner of using a potentiostat for studying scientific and technical problems, by insisting that, in corrosion studies, there is value in making electrochemical studies cojointly with studies of the surface state and with metallurgical studies, and in not drawing conclusions without taking into account results of corrosiometric tests of various types, selected in relation to the problem to be resolved.