Alkaline Direct Methanol Fuel Cell

Abstract

Polymer electrolyte membrane based direct methanol fuel cells (PEM-DMFC) have a complicated system design, and their fuel efficiency is limited by methanol cross-over through the proton exchange membrane. In addition, the methanol oxidation kinetics as well as oxygen reduction kinetics are quite slow in the acid electrolyte system. In contrast to acid DMFCs, it is known that electro-oxidation (and oxygen electro-reduction) reactions are improved in basic media. Alkaline DMFCs, unlike their acid counterparts, do not require MEAs, presently the most costly and complex stack component. It is however unknown if alkaline DMFC could be used as PEM alternatives for portable power applications. The technical challenge then, is to develop AFC stacks that can be used to fabricate compact low-power (20 W) systems that have sufficient resilience to carbonate build-up inherent in alkaline cells. In addition to carbon dioxide from ambient air, the methanol fuel is an additional source of electrolyte carbonation (CO2 generated in situ). For portable power applications, one way to circumvent this issue is to replenish the spent alkaline electrolyte on a regular maintenance schedule. This paper reports the results of some preliminary work carried out to investigate the viability of alkaline DMFC for portable power application.