Comparison of different types of membrane in alkaline direct ethanol fuel cells

It has been understood that the use of cation-exchange membranes (CEM) and alkali-doped polybenizimidazole membranes (APM) in alkaline direct ethanol fuel cells (DEFC) with an added base in the fuel exhibits performance similar to the use of anion-exchange membranes (AEM). The present work is to assess the suitability of the three types of membrane to alkaline DEFCs by measuring and comparing the membrane properties including the ionic conductivity, the species permeability, as well as the thermal and mechanical properties. The comparison shows that: (i) the AEM is still the most promising membrane for the alkaline DEFC, although the thermal stability needs to be further enhanced; (ii) before solving the problem of the poor thermal stability of AEMs, the CEM is another choice for the alkaline DEFC running at high temperatures (<90 °C); and (iii) the APM can also be applied to the alkaline DEFC operating at high temperatures, but its mechanical property needs to be substantially enhanced and the species permeability needs to be dramatically decreased.