Alkali doped poly(vinyl alcohol) for potential fuel cell applications

Optical transparent, chemically stable alkaline solid polymer electrolyte membranes were prepared by incorporation KOH in poly(vinyl alcohol) (PVA). The distributions of oxygen and potassium in the membrane were characterized by XRD and SEM-EDX. It is demonstrated that combined KOH molecules may exist in the PVA matrix, which allow it to be an ionic conductor. In particular, the chemical and thermal stabilities were investigated by measuring changes of ionic conductivities after conditioned the membrane in various alkaline concentrations at elevated temperatures for 24h for potential use in fuel cells. The membranes were found very stable even in 10 M KOH solution up to 80 degrees C without losing any membrane integrity and ionic conductivity due to high dense chemical cross-linking in PVA structure. The measured ionic conductivity of the membrane by AC impedance technique ranged from 2.75 x 10(-4) S cm(-1) to 4.73 x 10(-4) S cm(-1) at room temperature, which was greatly increased to 9.77 x 10(-4) S cm(-1) after high temperature conditioning at 80 degrees C. Although, a relatively higher water uptake, the methanol uptake of this membrane was one-half of Nafon 115 at room temperature and 6 times lower than that of Nafion 115 after conditioned at 80 degrees C. The membrane electrolyte assembly (MEA) fabricated with PVA-KOH in direct methanol fuel cell (DMFC) mode showed an initial power density of 6.04 mW cm(-2) at 60 degrees C and increased to 10.21 mW cm(-2) at 90 degrees C. 2009 Elsevier B.V. All rights reserved.