Electrochemistry electrode kinetics

Jan. 26, 1927, Farnborough, Great Britain - July 9, 2005, Ottawa, Canada) Canadian electrochemist, 1946-1949 Imperial College, London University, thesis on -> electrocatalysis and corrosion inhibitors (supervisor J.O M. Bockris), 1949-1954 Chester-Beatty Cancer Research Institute with J.A.V. Butler on DNA, 1954-1955 post-doc at University of Pennsylvania with J.O M. Bockris (among other subjects -> proton -+ mobility, the effect of field-induced reorientation of the water molecule), since 1956 professor at the University of Ottawa (Canada), more than 400 publications on physical electrochemistry, electrode kinetics and mechanisms, - electrochemical capacitors. 

Voltammetric detection of a solution species normally depends on that species being reduced or oxidized at the electrode. Frequently in electrochemistry electrode kinetics are such that the redox reaction occurs at more positive or negative potentials than predicted on the basis of thermodynamics. Modification of electrode surfaces with redox centers that can mediate charge transfer to the analyte, as depicted in Fig. 10.2, may reduce this overpotential to allow the analyte to be detected within the electrolyte potential window and to bring the redox potential into a region where electroactive interferences are reduced. In addition to shifting the operating formal potential of the analyte species, modified electrodes can also increase the rate of the reaction over that observed at unmodified electrode surfaces. 

Other Coordination Complexes. Because carbonate and bicarbonate are commonly found under environmental conditions in water, and because carbonate complexes Pu readily in most oxidation states, Pu carbonato complexes have been studied extensively. The reduction potentials vs the standard hydrogen electrode of Pu(VI)/(V) shifts from 0.916 to 0.33 V and the Pu(IV)/(III) potential shifts from 1.48 to -0.50 V in 1 Tf carbonate. These shifts indicate strong carbonate complexation. Electrochemistry, reaction kinetics, and spectroscopy of plutonium carbonates in solution have been reviewed (113). The solubiUty of Pu(IV) in aqueous carbonate solutions has been measured, and the stabiUty constants of hydroxycarbonato complexes have been calculated (Fig. 6b) (90). 

Adams, R. N., Electrochemistry at Solid Electrodes, M. Dekker, New York, 1969. Albery, W. J., Electrode Kinetics, Oxford University Press, 1975. 

Markov chains theory provides a powerful tool for modeling several important processes in electrochemistry and electrochemical engineering, including electrode kinetics, anodic deposit formation and deposit dissolution processes, electrolyzer and electrochemical reactors performance and even reliability of warning devices and repair of failed cells. The way this can be done using the elegant Markov chains theory is described in lucid manner by Professor Thomas Fahidy in a concise chapter which gives to the reader only the absolutely necessary mathematics and is rich in practical examples. 

As is well known in the field of electrochemistry in general, electrode kinetics may be conveniently examined by cyclic voltammetry (CV) and by frequency response analysis (ac impedance). The kinetics of the various polymer electrodes considered so far in this chapter will be discussed in terms of results obtained by these two experimental techniques. 

J. O M. Bockris, Chem. Rev. 3 525 (1948) (hydrogen oriented) Modem Aspects of Electrochemistry, Vol. 1, Ch. 4, Butterworths, London (1954). Firstcomprehensive article on electrode kinetics as such. 

A discussion of the effects of the structure of the interface on electrode kinetic rates is the right moment to introduce a seminal figure in electrochemistry, a person who played a part later than—but hardly less than—that of Butler and of Volmer and Erdey-Gmz, in establishing the basis of the modem subject. It was A. N. Frumkin who first introduced interfacial structure considerations into electrode kinetics, in 1932. However, to leave a mention of Frumkin at that would sadly underdescribe a great leader whose influence in creating physical electrochemistry was outstanding.16... 

H. Gerischer, Semiconductor Electrode Reactions, in Recent Advances in Electrochemistry, P. Delahay, ed., Interscience, New York (1961). Electrode kinetics involving conductivity and valence bands. 

References 1—7 give a comprehensive and classic overview of electrode kinetics, while the electrochemical nomenclature followed here has been normalized by the Commission on Electrochemistry of the International Union of Pure and Applied Chemistry (IUPAC) [8, 9]. 

AC/ is known as the overpotential in the electrode kinetics of electrochemistry. Let us summarize the essence of this modeling. If we know the applied driving forces, the mobilities of the SE s in the various sublattices, and the defect relaxation times, we can derive the fluxes of the building elements across the interfaces. We see that the interface resistivity Rb - AC//(F-y0) stems, in essence, from the relaxation processes of the SE s (point defects). Rb depends on the relaxation time rR of the (chemical) processes that occur when building elements are driven across the boundary. In accordance with Eqn. (10.33), the flux j0 can be understood as the integral of the relaxation (recombination, production) rate /)(/)), taken over the width fR. 

Accordingly, the potential dependence of the electrode kinetics is determined by the variation of the activation energy with E, which is established by the position of the transition state on the energy profile in Fig. 1.13. This key aspect has been addressed in different ways by the different kinetic models developed. In the following sections, the two main models employed in interfacial electrochemistry will be reviewed. 

Bioelectrochemistry is hardly a new area—it led to a Nobel prize in the 1950s—but its theory has hitherto been based on older Nernstian principles, and this type of thinking in electrophysiology involves a conservation that slows the introduction of interfacial electrode kinetics in newer treatments. Metabolism, nerve conduction, brain electrochemistry—these areas are where the mechanism of the processes, as yet poorly understood, certainly involve electric currents and are most probably electrochemical. 

M. Green, Semiconductor Electrochemistry, in Modern Aspects of Electrochemistry, J. O M. Bockris and B. E. Conway, eds., Vol. 2, Ch. 2, Plenum, New York (1959). First formulation of semiconductor electrode kinetics in terms of equations band bending surface states limiting currents. 

Fleig reviews fundamental aspects of solid state ionics, and illustrates many similarities between the field of solid state electrochemistry and liquid electrochemistry. These include the consideration of mass and charge transport, electrochemical reactions at electrode/solid interfaces, and impedance spectroscopy. Recent advances in microelectrodes based on solid state ionics are reviewed, along with their application to measuring inhomogeneous bulk conductivities, grain boundary properties, and electrode kinetics of reactions on anion conductors. 

Let us consider the electrode kinetics associated with charge transfer from an n-type semiconductor particle to an electrode. As indicated by Albery et al. [164], the crucial difference between the electrochemistry of a colloidal particle and an ordinary electrochemically active solution phase species is the number of electrons transferred from the particle to the electrode may be large and will depend upon the potential of the electrode. Fig. 9.5 shows the model for an encounter of a particle with an electrode used by Albery and co-workers. kD is the mass-transfer coefficient for the transport of the particles to the electrode surface. In the simplest case, wherein it is assumed that the lifetime of the transferable electrons (majority carriers of thermal or photonic origin) is greater than the time taken by a particle to traverse the ORDE diffusion layer, this is given by... 

Refs. [i] Horiuti /, Poldnyi M (1935) Acta Physicochim URSS 2 505 [in English (2003) J Molecular Catalysis A199 185] [ii]Gileadi E (1993) Electrode kinetics. VCH, New York, pp 106-126 [iii] PletcherD (1991) A first course in electrode processes. The Electrochemical Consultancy, Hants, pp 90-94 [iv] Bard A], Faulkner LR (2001) Electrochemical methods, Wiley, New York, pp 87-124 [v] Hamann CH, Hamnett A, Vielstich W (1998) Electrochemistry. Wiley-VCH, Weinheim, pp 306-307... 

Refs. [i] Bockris JO M, Reddy AKN, Gamboa-Aldeco M (2000) Modern electrochemistry, fundamentals of electrodics, 2nd ed, vol. 2A. Kluwer, New York, p 1048 [ii] Mayneord WV (1979) Biographical memoirs of fellows of the Royal Society 25 144 [Hi] Butler JAV (1924) Trans Faraday Soc 19 729 [iv] Butler JAV (1924) Trans Faraday Soc 19 734 [v] Erdey-Gruz T, Volmer M (1930) Zphys Chem 150A 203 [vi] Butler JAV (1935) The fundamentals of chemical thermodynamics elementary theory and electrochemistry, 2nd edn. Macmillan, London [vii] Delahay P (1965) Double layer and electrode kinetics. Interscience, New York, pp 154-159 [viii] Butler JAV (1951) (ed) Electrical phenomena at interfaces, in chemistry, physics and biology. Methuen, London... 

Refs. [i] Gileadi E (1993) Electrode kinetics. VCH, New York, p 53, 127 [ii] Bockris JO M, Reddy AKN (2006) Modern electrochemistry. Springer, New York [Hi] Bard AJ, Faulkner LR (2001) Electrochemical methods. Wiley, New York [iv] Parsons R (1974) Pure Appl Chem 37 503 [v] Parsons R (1979) Pure Appl Chem 52 233 [vi] Mills I, Cvitas T, Homann K, Kallay N, Kuchitsu K (eds) (1993) IUPAC quantities, units and symbols in physical chemistry. Blackwell Scientific Publications, Oxford, p 58, 60... 

Refs. [i] Frumkin A (1933) Z phys Chem A 164 121 [ii] Frumkin AN (1961) Hydrogen overvoltage and adsorption phenomena, part 1, mercury. In Delahay P (ed) Advances in electrochemistry and electrochemical engineering, vol 1. Interscience, New York [iii] Frumkin AN, Petrii OA, Nikolaeva-Ferdorovich NV (1963) Electrochim Acta 8 177 [iv] Frumkin AN, Nikolaeva-Fedorovich NV, Berezina NP, Keis KhE (1975) J Electroanal Chem 58 189 [v] Fawcett WR (1998) Double layer effects in the electrode kinetics of electron and ion transfer reactions. In Lipkowski J, RossPN (eds) Electrocatalysis. Wiley-VCH, New York, p 323... 

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