Structural parameters of porous gas diffusion electrodes and their components

Gas diffusion electrodes used in metal air batteries and fuel cells serve not only as the reaction zone for the energy producing fuel conversion, they also provide pores for gas diffusion and act as barrier for the electrolyte. Teflon-bonded multilayer carbon electrodes have been prepared using standard electrode fabrication procedures and are subjected to performance testing in 12N KOH. Electronmicroscopic and intrusion porosimetric techniques have been used to correlate electrode performance with structural parameters. Thermal pretreatment of the carbon materials did not only increase the lifetime of the electrodes, the increase in surface area and porosity was found to have beneficial effects on electrode performance. The potential difference experienced in fuel cell cathodes between oxygen and air operation was found to depend mainly on the porosity of the gas diffusion zone which can be adjusted by the amount and size of filler materials used