Polarization mass transport free

Fig. 21 (a) Polarization losses in a fuel cell. Cathode losses are significant and (b) Catalyst performance parameter extraction from IR and mass transport free polar curve. Tafel slope = 85 mV/decade at 70°C. 

The experimental plots of iR-free voltage vs. current density obtained for O2 or air and hydrogen as a fuel have been used for the estimation of the factors, which determine the cell polarization losses, namely activation potential, Tafel slope, and mass transport limitations. 

A conceptual polarization curve that would be obtained in the absence of mass transport and ohmic resistances can be constructed by extrapolating the /R-free cell voltage obtained at low current densities (< 0.1 A/cm ) by means of Equation 23.10, indicated by the square symbols in Figure 23.3 [10]. In the Tafel equation, the Tafel slope b is... 

Abstract Analytical solution of the associative mean spherical approximation (AMSA) and the modified version of the mean spherical approximation - the mass action law (MSA-MAL) approach for ion and ion-dipole models are used to revise the concept of ion association in the theory of electrolyte solutions. In the considered approach in contrast to the traditional one both free and associated ion electrostatic contributions are taken into account and therefore the revised version of ion association concept is correct for weak and strong regimes of ion association. It is shown that AMSA theory is more preferable for the description of thermodynamic properties while the modified version of the MSA-MAL theory is more useful for the description of electrical properties. The capabilities of the developed approaches are illustrated by the description of thermodynamic and transport properties of electrolyte solutions in weakly polar solvents. The proposed theory is applied to explain the anomalous properties of electrical double layer in a low temperature region and for the treatment of the effect of electrolyte on the rate of intramolecular electron transfer. The revised concept of ion association is also used to describe the concentration dependence of dielectric constant in electrolyte solutions. 

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