Development of polyvinyl alcohol based membranes for fuel cell applications

Development of polyvinyl alcohol based membranes for fuel cell applications

Abstract

Fuel cells are attractive energy conversion devices for transportation and portable applications due to their high efficiency and low emission. Among several types of fuel cells, polymer electrolyte membrane fuel cells (PEMFC) are regarded as promising options for electrical vehicles. The proton conducting membrane is the vital component of any PEMFC which makes it possible to attain high power densities. Nafion membrane, a perfluorinated sulfonated ionomer developed by Dupont shows high proton conductivity (~0.1 S/cm) at fully hydrated state, excellent mechanical properties and thermal stability. The main limitations of Nafion are its barrier properties. Many alternative membranes like poly(vinyl alcohol) (PVA) based membranes show good proton conductivity with low methanol permeability. PVA membranes are poor proton conductors as compared to Nafion membrane. Introduction of negatively charged ion groups in the PVA membrane can be achieved by chemical modification through crosslinking using Sulfo Succinic Acid (SSA). To increase the operating temperature of PEMFCs to 120 ?C, membranes that retain water and conductivity and that are more thermally and mechanically robust at high temperatures, are needed. Sulfonated poly (ether ether ketone) is the one that shows tremendous potential. The objective of this work is to develop and study novel blends of SPEEK with crosslinked PVA as membrane materials with lower water uptake and better mechanical stability and good proton conductivity. The proton conductivity, water uptake and ion exchange capacity were studied as a function of relative humidity, temperature and blend composition to evaluate the potential of these blends as as viable PEM for fuel cell applications. The wetting characteristics of proton conducting membranes are important in understanding the water uptake features of the membranes. We also investigated the effects of drying on the surface energy and wetting characteristics of PVA/SSA membranes.