First-order electrode, definition

In this equation, Cqx,s Cred,s represent, respectively, the concentrations of et Bred 1 the electrode surface. The expression (4.26) represents the Butler-Volmer equation for any first-order electrode reaction. Its rate, by definition, is proportional to the reactant concentration at the electrode surface. 

The reactions of DPAt and radical cations of other aromatic hydrocarbons with pyridine and substituted pyridines are among the most intensively studied electrode reactions of positive ions. The first definitive study of the mechanism of the reaction employed the rotating disk electrode (Manning et al 1969). Data were found to fit ECE working curves (Fig. 21) for the reactions of DPA7 with 4-cyanopyridine, 4-acetoxypyridine, pyridine and 4-methylpyridine. Pseudo first order rate constants of about 3, 10, 30, 300... 

Acar and coworkers (46] and Shapiro et al. [52] have presented general models based on the first of these two approaches. These models predict that the contaminant and the electrolysis products at inert electrodes will be transported and dispersed by advection, migration, and diffusion. Modelling in this manner provides only a first-order, mathematical framework to examine the flow patterns and chemistry generated in the process adsorption/desorption kinetics, acld/base chemical reactions, complex equilibria, and precipitatlon/solubility factors may heavily influence the model accuracy and outcome of any site remediation. Two approaches for mathematic modelling are the use of analytical solutions or numerical, finite element methods (FEM). Both models require adequate definitions for the boundary conditions (nature of electrolyses, flow behaviour). 

Of practical importance are electrochemical systems with electrodes. Electrical and gravitational systems may be of a pseudo first order with respect to charge and mass additions, when only the contribution of the external field to the energy is considered. However, this does not mean that these electrical and gravitational contributions should be included into the Gibbs -Duhem equation [16]. Of course, it is a matter of definition of the thermodynamic variables, whether the thermodynamic similarity exists or not. 

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