Oxygen evolution reaction kinetics

Platinum has also had its share of attention in recent years. The effect of phosphoric acid concentration on the oxygen evolution reaction kinetics at a platinum electrode using 0-7 m-17-5 m phosphoric acid at 25°C has been studied with a rotating disc electrode . The characteristics of the ORR are very dependent on phosphoric acid concentration and H2O2 is formed as an intermediate reaction. Also, platinum dissolution in concentrated phosphoric acid at 176 and 196°C at potentials up to 0-9 (SHE) has been reported . 

Figure 4. Polarization curves of carbon corrosion and oxygen evolution reactions based on measured carbon corrosion kinetics for Pt/Vulcan and Pt/Graphitized-Vulcan and oxygen evolution kinetics for Pt/C catalysts. The upper horizontal dotted line denotes a current density equivalent to oxygen crossover through membrane from cathode to anode.

An increasing amount of attention is being given to oxides as possible anodes for oxygen evolution because of the importance of this reaction in water electrolysis. In this connection, numerous studies have been carried out on noble metal oxides, spinel and perovskite type oxides, and other oxides such as lead and manganese dioxide. Kinetic parameters for the oxygen evolution reaction at a variety of single oxides and mixed oxides are shown in Table 3. 

Kinetic parameters for the oxygen evolution reaction on various oxides... 

In the discussion of the hydrogen and oxygen evolution reactions, we saw that the current-potential relationship is influenced, and sometimes determined completely, by the potential dependence of the coverage 9. Thus, one may expect that the kinetic parameters will depend on the adsorption isotherm, which relates the surface concentration to the bulk concentration, and more importantly in electrochemistry, to the potential. In the preceding derivations it was tacitly assumed that the Langmuir isotherm applies. In Section 19 we discuss the limitations of this assumption and show how the kinetic parameters change when different isotherms are applicable. 

XVII. Electrocatalysis and Kinetic Behavior of Oxygen Evolution Reaction... 

S. Trasatti, Electrode kinetics and electrocatalysis of hydrogen and oxygen electrode reactions. 4. The oxygen evolution reaction, in Electrochemical Hydrogen Technologies (Ed. H. Wendt), Elsevier, Amsterdam, 1990, pp. 104-135. 

In order to avoid such complicated expressions, the quasi-equilibrium method is used, although the above steady-state approach can become reduced to the same result if various limiting assumptions about relative values of rate constants, referred to earlier, are introduced. This approach assumes a rate-limiting step so that all other steps are supposed to have much larger rate constants (in both directions) and hence are all in virtual or quasi -equilibrium. Bockris " applied a similar treatment in a less general way to the kinetics of various pathways of the oxygen evolution reaction. With the application of a negative overpotential that drives the forward, supposed reductive direction of the reaction, each of the steps prior to the rds (which are hence limited by it) will be at quasi-equilibrium. 

Electrochemical Oxygen Evolution. Thermodynamically, the oxygen evolution reaction is favoured over the chlorine evolution reaction in aqueous solutions because the standard reversible potential is 1.23 V for the oxygen evolution reaction and 1.35 V for the chlorine evolution reaction. However, because of the slow kinetics of the oxygen evolution... 

Kinetics and Mechanisms of the Oxygen Evolution Reaction on Meta and Oxide Electrodes... 

The quantitative and theoretically significant approaches to the study of the electrode kinetic reactions have been established only within the last twenty years. These methods have been applied in the study of only a few electrochemical systems, particularly the hydrogen and oxygen evolution reactions. Further, these approaches have been seldom applied for the elucidation of mechanisms of the anodic oxidation of organic compounds. The recent literature indicates a trend toward methods which give large amounts of data in relatively short times but which do not lend themselves easily to quantitative analysis. Thus, it seems desirable at this point to review the experimental methods which may be profitably used in the study of organic reactions at anodes. 

Krishtalik LI (1981) Kinetics and mechanism of anodic chlorine and oxygen evolution reactions on transition metal oxide electrodes. Electrochim Acta 26 329-337. doi 10.1016/0013-4686(81)85019-0... 

Davidson CR, Kissel G, Srinivasan S (1982) Electrode-kinetics of the oxygen evolution reaction at NiCo204 from 30-percent KOH - dependence on temperature. J Electroanal Chem 132 129-135... 

Fig. 6.3 Fundamental principle of semiconductor-based photocatalytic water splitting for hydrogen generation. CB conduction band VB valence band Eg bandgap OER oxygen evolution reaction HER hydrogen evolution reaction WRC water reduction co-catalysts WOC water oxidation co-catalysts SBR surface back reaction AEo and AE/, kinetic overpotentials for OER and HER, respectively...

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