1.2.2.1 Polarization Curves and Performance
Usually, the open circuit voltage of a polymer electrolyte DMFC is significantly lower than the thermodynamic or reversible potential for the overall process. This is mainly due to methanol crossover that causes a mixed potential at the cathode and to the irreversible adsorption of intermediate species at electrode potentials close to the reversible potential [6–19]. The coverage of methanolic species is large at high cell potentials, that is, at low anode potentials. This determines a strong anode activation control that reflects on the overall polarization curve (Figure 1.2). In Figure 1.2, the terminal voltage of the cell is deconvoluted into the anode and cathode polarizations: