Electrodes kinetics and electrocatalysis

Trasatti, S. (1990) Electrode kinetics and electrocatalysis of hydrogen and oxygen electrode reactions. 1. Introduction, in Electrochemical Hydrogen Technologies (ed. 

Wendt, H. and Plzak, V. (1990) Electrode kinetics and electrocatalysis of hydrogen and oxygen electrode reactions. 2. Electrocatalysis and electrocatalysts for cathodic evolution and anodic oxidation of hydrogen, in Electrochemical Hydrogen Technologies (ed. H. Wendt), Elsevier, Amsterdam, Chapter 1. 2. 

Electrode Kinetics and Electrocatalysis in Molten Carbonate Fuel Cells... 

One of the most fruitful trends in the comprehension and control of electrochemical reaction kinetics and electrocatalysis has been the development of modified electrodes to achieve redox mediators of solution processes. This strategy is based on the electrochemical activation (through the application of an electrical perturbation to the electrode) of different sites at a modified surface. As a result of this activation, the oxidation or the reduction of other species located in the solution adjacent to the electrode surface (which does not occur or occurs very slowly in the absence of the immobilized catalyst) can take place4 [40, 69, 70]. 

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. 

Sep. 26,1924, Orange, NJ, USA - Mar. 8, 2002, Cleveland, OH, USA) American electrochemist BA Montclair State University 1945 MS Western Reserve University 1946, Cleveland PhD in physical chemistry Western Reserve University 1948, Cleveland. At Western Reserve University, associate professor (1948-1958) then professor (1958-1990) and, since 1983, Frank Hovorka Professor founder of Case Center of Electrochemical Sciences 1976 retired 1990 more than 270 publications editor or co-editor of 20 books research on -> electrode kinetics, - spectroelectrochemistry, - electrocatalysis, ultrasound. Ref. (2002) The Electrochemical Society, Interface 11(1) 10... 

Electrocatalysis Using a material to enhance electrode kinetics and minimize overpotential. 

The present chapter has presented a comprehensive review of electrode kinetic and catalytic aspects associated with methanol, ethanol, and formic acid oxidation. The prevalent point of view in selecting and organizing the vast amount of information in this area was that of practical applicability in order to advance the technology of direct fuel cells. Emphasis was placed on the catalytic system , starting with catalyst preparation methods and focusing on the interaction of catalyst/support/ionomer/chemical species. The development of catalytic systems was followed, from fundamental electrochemical and surface science studies to fuel cell experiments (whenever experimental data was available). Advances in both fundamental electrocatalysis and electrochemical engineering hold promise for the development of high-performance and cost-effective direct liquid fuel cells. 

The aim of this review is to first provide an introduction of electrocatalysis with the hope that it may introduce the subject to non-electrochemists. The emphasis is therefore on the surface chemistry of electrode reactions and the physics of the electrode electrolyte interface. A brief background of the interface and the thermodynamic basis of electrode potential is presented first in Section 2, followed by an introduction to electrode kinetics in Section 3. This introductory material is by no means comprehensive, but will hopefully provide sufficient background for the rest of the review. For more comprehensive accounts, please see texts listed in the references.1-3... 

In recent years, electrochemical charge transfer processes have received considerable theoretical attention at the quantum mechanical level. These quantal treatments are pivotal in understanding underlying processes of technological importance, such as electrode kinetics, electrocatalysis, corrosion, energy transduction, solar energy conversion, and electron transfer in biological systems. 

Cells can be made in which the cathode-anode distance is only 10-3 cm. Such cells have the advantage that the total impurity present is veiy small and may not be enough to cover more than 0.1% of the electrode surface if they were all adsorbed. Thus, suppose the impurity concentration were 10-6 mol liter-1 or 10-9 mol cc 1 or 10 12 mol in the cell Because an electrode surface can cany (at most) about 10-9 mol cm-2, the maximum fraction of the surface covered with impurity molecules is 0.1%. Does work with thin-layer cells eliminate the inpurity problem in electrode kinetics It improves it. However, active sites on catalysts may occupy less than 0.1% of an electrode and preferentially attract newly arriving impurities, so that even thin-layer cells may not entirely avoid the impurity difficulty,32 particularly if the electrode reaction concerned (as with most) involves adsorbed intermediates and electrocatalysis. 

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... 

Surface modification of electrodes to facilitate electrocatalysis parallels in many respects the chemistry discussed above for immobilization of catalysts on organic and inorganic materials. However, the objectives are somewhat different in electrode modification. Specifically, the principle objectives in electrode modification are usually to alter electrode stability, to alter the kinetics of reactions at electrode surfaces, or to alter an electrodes electrochemical properties. Electrode modification may involve covalent attachment of electroactive compounds or coating of the electrode surface with a polymeric phase. 

The kinetics of electrochemical reactions are often modified by the nature of the electrode material, and by the presence of atomic and molecular species either adsorbed on the surface or in the bulk solution [14]. Electrocatalysis is primarily concerned with the study of this phenomenon and, particularly, with the factors that govern enhancements in the rates of redox processes. Implicit in this general statement is the ability of the species responsible for these effects, or electrocatalyst, or the electrode itself, to carry out the reaction numerous times before undergoing possible deactivation. Electrocatalytic processes in which the electrode simply serves as a source or sink of electrons to generate solution phase species that... 

Understanding the activity and selectivity properties of electrocatalysts requires the characterization of catalyst surfaces, determination of adsorption characteristics, identification of surface intermediates and of all reaction products and paths, and mechanistic deliberation for complex as well as model reactions. Electrochemical and classical methods for adsorption studies are well documented in the literature (5, 7-9, 25, 24, 373. Here, we shall outline briefly some prominent electrochemical methods and some nonelectrochemical techniques that can provide new insight into electrocatalysis. Electrode kinetic parameters can be determined by potentionstatic methods using the methodology of Section II1,D,3. 

The opponents of fundamental studies with idealized electrocatalysts and reactions cannot deny the unique insight into surface molecular and electronic or energetic interactions that new surface and mechanistic techniques generate. A combination of surface spectrometries, isotopic reactions, and conventional electrode kinetics could help unravel some of the surface mysteries. The application of such methods in electrocatalysis is limited at present to hydrogen and oxygen reactants on simple catalytic surfaces. Extension to a variety of model and complex reactions should be attempted soon. The prospective explorer, however, should strive and attend with care the standardization of analytical methods for meaningful interpretations and comparisons. 

Hydrogen evolution has been found without exception to be inhibited by adlayers of Bi, As, Cu, and Sn on Pt [141-143], Pb, Tl, and Cd on Pt [144, 145] and Au [144, 145], and by Pb and Tl on Ag [146] electrodes. All these metals exhibit a large overpotential for hydrogen evolution. Adlayers inhibiting H2 evolution are of interest for fundamental electrocatalysis and electrode kinetics, but they also have practical significance in promoting sorption of H into... 

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