Water movement through an anion exchange membrane fuel cell (AEMFC): Influence of gas humidity and flow rate

Abstract

The water movement between the anodic and cathodic sides of a fuel cell (AEMFCs) motivated the analysis of the effect exerted by the operational conditions on the water direction using a commercial anion exchange membrane (IONOMR®). This work shows the capability to favor the electro-osmotic drag (EOD) or the diffusion water transport mechanisms under different gas flow rates and humidities. Accordingly, the results demonstrated that the EOD predominance was promoted when low symmetric flow rates (125 cm3 min−1 for anode and cathode) were used in the AEMFC, suggesting membrane dehydration. On the contrary, the water diffusion dominance appears under asymmetric flow rates between anode and cathode (125 and 250 cm3 min−1, respectively); under these conditions, the membrane dehydration might be suppressed by anode flooding alleviation. The AEMFC performance was affected by the water transport mechanism, giving lower peak power densities for EOD-dominated systems (35.2 mW cm−2 at 60 °C) than those obtained by diffusion (62.8 mW cm−2 at 60 °C). The most suitable operating condition is under water-diffusion at non-saturated streams (below 65%), where a decrease in performance is experienced as the humidifier temperature increases from 60 °C to 80 °C (supersaturated flow), giving peak power densities of 62.8 and 3.7 mW cm−2, respectively.