Cross-linked poly(vinyl alcohol)/poly (diallyldimethylammonium chloride) as anion-exchange membrane for fuel cell applications

Abstract

The novel, low-cost anion-exchange membranes (abbreviated as PVA/PDDA-OH−), made from poly(vinyl alcohol) and poly(diallyldimethylammonium chloride) blends, are successfully synthesized by a combined thermal and chemical cross-linking technique. The hydroxide (OH−) conductivity, water uptake, ion exchange capacity (IEC), thermal stability, oxidative stability and alkaline stability of PVA/PDDA-OH− membranes are measured to evaluate their applicability in alkaline fuel cells. The effects of cross-linking procedure, cross-linking time and membrane composition on OH− conductivity are studied using AC impedance technique. It is found that by cross-linking modifications, the membranes exhibit excellent thermal stability with onset degradation temperature high above 170 °C, a relatively high oxidative stability at 60 °C, and a strong alkaline stability in 8 M KOH at 80 °C. High OH− conductivity of 0.025 S cm−1 is achieved at 25 °C and reaches up to 0.037 S cm−1 at 80 °C. For exploring the conducting mechanisms, the concentration and mobility of charge carries of the membranes are also measured. The H2/O2 fuel cell tests with PVA/PDDA-OH− membranes yield the peak power density of 11.5 mW cm−2 and greatly increase to 35.1 mW cm−2 depending on PVA/PDDA mass ratio, on a low metal loading on both the anode and the cathode of 0.5 mg (Pt) cm−2 at ambient temperature.