Membrane electrode assembly constituents

As explained in a previous section, a membrane electrode assembly (MEA) consists of the polymer membrane that is sandwiched between an anode and a cathode electrode, respectively. The electrodes are composed of a conductive carbon network that supports a catalyst on a gas diffusion layer. An additive, such as polytetra-fluoroethylene (PTEE), helps bind the Pt/C catalyst to the gas diffusion layer. At the anode, the catalyst facihtates the oxidation of hydrogen into its constituent electrons and protons. As the protons are passed through the acid-doped membrane to the cathode, the electrons are passed through an external circuit, thereby creating electricity. Einally, the electrons and protons react with oxygen at the cathode electrode to form water as the final reaction product. 

Fig. 3 Proposed pathway of membrane electrode assembly (MEA) and GDL interaction leading to observed hydrophobicity loss of GDL constituent materials...

Under tlie circumstances, it is reasonable to say that the reaction kinetics on the surface of carbon electrode is facilitated and hence the activation overpotential is not observed. However, the system resistance such as electrode, electrolyte, polymer electrolyte membrane, and carbon block could be dominant, influencing cell overpotential over all current ranges. Therefore, it is necessary to reduce the system resistance by selecting the cell constituents with low resistance and optimising the cell assembly. 

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