Coupled half-cell reactions kinetics

In Chapter 4, analysis of the kinetics of coupled half-cell reactions shows how the corrosion potential and corrosion current density depend on the positions of the anodic and cathodic polarization curves. The anodic polarization curves are generally represented as showing linear or Tafel behavior, and the cathodic curves are shown with both Tafel and... 

Hu et al. also report the modeling of MEA and carbon corrosion based on four electrochemical and one chemical reactions taking place within the MEA (Hu et al, 2009). The two-dimensional model considers coupled transport of charged and noncharged species. The model was set up to solve for the local fuel starvation case and the start-up and shut-down case with the Butler-Volmer equation governing the kinetics of each half-cell reaction ... 

Consequently, a wealth of information on the energetics of electron transfer for individual redox couples ("half-reactions") can be extracted from measurements of reversible cell potentials and electrochemical rate constant-overpotential relationships, both studied as a function of temperature. Such electrochemical measurements can, therefore, provide information on the contributions of each redox couple to the energetics of the bimolecular homogeneous reactions which is unobtainable from ordinary chemical thermodynamic and kinetic measurements. 

Oxidation of CO is also important in fuel cell applications. By combining the half reaction for the CO2/CO couple, equation (a), with electrochemical reduction of O2, fuel cells may achieve a maximum open circuit potential given by IlSlfCOj/CO) - (02/H20) = 1.34 . In practice, electrocatalysts are required to lessen the normally high kinetic overpotentials for electrodic CO oxidation. An example of a CO/O2 fuel cell which operates at the relatively low T of 80°C by employing [Rh(CO)2Br2] as the electrocatalyst and the Rh couple to mediate CO oxidation is shown below . 

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