Electrocatalysis oxygen electrode reaction

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. 

At IREQ, besides the participation in the field tests run by the engineers of Hydro-Quebec (12), the main effort has been to tackle fundamental problems in the field of electrocatalysis (18-22) and of anodic oxidation of different potential fuels (23-26). A careful and extensive study of the electrochemical properties of the tungsten bronze has been carried out (18-20) the reported activity of these materials in acid media for the oxygen reduction could not be reproduced and this claim by other workers has been traced back to some platinum impurities in the electrodes. Some novel techniques in the area of electrode preparation are also under study (21,22) the metallic deposition of certain metals on oriented graphite show some interesting catalytic features for the oxygen reduction and also for the oxygen evolution reaction. 

Kawagoe KF, Johnson DC. Electrocatalysis of anodic oxygen-transfer reactions. Oxidation of phenol and benzene at bismuth-doped lead dioxide electrodes in acidic solutions. J Electrochem Soc 1994 141 3404—3409. 

Examples are the oxygen electrode, Equation (1), or the hydrogen electrode (i.e. the H+/H2 reaction), Equation (2). Electron transfer proceeds regularly with the reacting species adsorbed at an electrode surface. In many cases, electrocatalysis by the electrode metal plays an important role. Associated chemical reactions, such as protonation and dissociation, render the reaction mechanisms complex. This is true in particular for the oxygen electrode. 

P. N. Ross Jr, Oxygen reduction reaction on smooth single crystal electrodes, in Handbook of Fuel Cells, Electrocatalysis, John Wiley and Sons, Chichester, 2003, Vol. 2. 

The effect of the distance between the active center and the electrode on the reaction rate has been studied using as an example the electrocatalysis of the oxygen reduction reaction by laccase adsorbed on soot. Variation in the distance between the active center and the electroconductive substrate was achieved by inserting an intermediate monolayer of lipid molecules flatly and vertically oriented cholesterol molecules and vertically oriented lecithin molecules (scheme in Figure 36). In this case, the conditions of obtaining compact lipid monolayers were fulfilled. The subsequent setting of laccase did not lead to their desorption. 

Discrimination between the oxygen adsorption and oxide phase formation theories has important implications in electrocatalysis. If the adsorption theory is correct, then Pt metal should be considered the electrode material and the adsorbed oxygen-containing species as possible intermediates in the steady state electrode reactions of molecular oxygen or a competition with intermediates for adsorption sites. If the phase oxide theory is correct, then Pt oxide has to be considered as the electrode material with obvious consequences concerning the energies of adsorption of intermediates on Pt oxides and not on the bare metal. 

However, the electrochemical oxygen evolution reaction (OER) from the water in acid solutions is thermodynamically slightly more favorable than the CER given by Eq. 2 (the fP value for the OER is 1.229 V). Bearing in mind that electrocatalysis essentially implies the activity and selectivity of various electrode materials toward a certain electrode reaction [2], the correct choice of electrode material that is of high electrocatalytic activity for the CER and of lower activity for the OER is of extreme importance. Anyhow, CAT is always subjected to current loss due to the OER as a side reaction. This fact sets additional demands toward the anode material for the CER, i.e., its stability toward the OER and consequently its durability in CAT. 

Larew LA, Gordon JS, Hsiao Y, Johnson DC, Buttry DA (1990) Electrocatalysis of anodic oxygen-transfer reaction Applicatirai of an electrochemical quartz crystal microbalance to a study of pure and bismuth-doped beta-lead dioxide film electrodes. J Electrochem Soc 137 3071—3078... 

Steam electrolysis splits water in the form of steam into hydrogen and oxygen by use of electricity and thus can be used as a method to produce hydrogen. Unlike other types of electrolysis, e.g., alkaline water electrolysis and polymer electrolyte water electrolysis, the steam electrolysis operates typically at 700-1,000 °C since the electrolysis uses solid electrolyte that works at the high temperatures. Such high operation temperature leads to fast kinetics for the electrode reactions, so that precious metals are not necessary for the electrocatalysis. 

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