A carbon dioxide tolerant aqueous-electrolyte-free anion-exchange membrane alkaline fuel cell

Abstract

Despite over a century of study and decades of intensive research, few fuel cell products have appeared on the market.[1] The major inhibitor to mass commercialisation is cost.[2] H2/air alkaline fuel cells (AFCs) containing aqueous KOH electrolyte promise the lowest cost devices,[3, 4] with the ability to use non-Pt catalysts. The fundamental problem with AFCs is that the aqueous KOH electrolyte reacts with CO2 (cathode air supply) to form carbonate species, which lower the performance and lifetime of the cell (through formation of carbonate precipitates in the electrodes and by decreasing the concentration of OH-1 in the electrolyte).[4, 5] However, the carbonate content of an aqueous-electrolyte-free (metal-cation-free) alkaline anionexchange membrane (AAEM), that was pre-exchanged to the CO32- form, decreased when operated in H2/air and methanol/air fuel cells. This remarkable result is contrary to prior wisdom; AAEMs inherently prevent carbonate performance losses when incorporated into AFCs. This experiment was made possible only by the recent breakthrough development of an alkaline interface ionomer,[6] which allows fabrication of membrane electrode assemblies that do not require incorporation of metal hydroxides species to perform well.[7] © 2008 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim.