The effect of water permeability of AEMs on AMFC performance

Introduction The alkaline Membrane Fuel Cell (AMFC) uses anion conductive polymers as the alkaline electrolyte and has emerged as an alternative to proton exchange membrane fuel cells (PEMFC). The high pH value in its electrolyte allows to use non-precious metal catalysts or non-platinum catalysts. Its lower activation overpotential, especially for the oxygen reduction reaction (ORR) in the cathode has been pointed out, and good catalytic activities of such type of catalysts have been shown . However, several major issues have been pointed out which significantly hinder the development and practical application of AMFCs. One is rapid CO2 absorption into alkaline membranes. It was reported existence of CO2 in the air largely lowered the AMFC performance at 50C. Another is lower limitation in the operating temperature for MEAs due to the insufficient thermal stability of alkaline membrane and ionomers. As other feature of AMFC, it had been pointed out that AMFC might make water management issue easier compared to PEMFC. It is because AMFC generates water at anode and the direction of electro-osmosis is opposite, cathode to anode. However, AMFC consumes water for oxygen reduction reaction (ORR) at cathode. So far, it had been shown that water required for ORR was mainly supplied from anode side by measurement of net water flux across AEM. Therefore, it has to be taken into account how to supply sufficient amount of water to cathode for AMFC`s water management. AEM is one of the key components of MEA which might affect the water behavior within operating AMFC. It is worth to study the effect of AEMs on AMFC performance. Tokuyama Corp, Japan, has been developing alkaline membranes and ionomers for AMFC. In this study, the effect of AEM`s permeability on AMFC performance was studied with different types of developing materials.