Fuel permeability of anion exchange membranes under electric field

The development of membranes with high ionic conductivity and low fuel permeability is a key for the fuel cell researches. However, the understanding of the fuel permeability in an operating cell is far from clear. In this work, a fuel permeability test device under the electric field was established for the first time to simulate the actual permeation of fuel across the anion exchange membranes (AEMs) during operating. Two kinds of AEMs (blank AEM and Co-AEM) were tested to investigate the effects of electric field and membrane component on the fuel permeability of the membranes. The Co-AEM showed much higher ionic conductivity and little lower fuel permeability than the blank AEM without electric field. As the electric field increased, the fuel permeability of the blank AEM continuously increased while that of the Co-AEM gradually decreased. The different change of the fuel permeability between the blank AEM and the Co-AEM resulted from the catalytic effect of Co-species which promoted the hydrolysis and electrical oxidization of borohydride. The high ionic conductivity and low fuel permeability of the Co-AEM, especially under electric field, resulted in the low polarization rate of cathode and high power density of the direct borohydride fuel cell using the Co-AEM.