Development of nafion based nanofibres

The aim of this thesis work was to develop Nafion based nanofibres for the potential use in fuel cells. The electrospinning of pure Nafion is not possible. Thus a carrier polymer should be used. Poly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO) and thermoplastic polyurethane (TPU) were selected as carrier polymers in this study. In the first stage of the study, Nafion/carrier polymer/solvent mixtures with different mixing ratios were electrospun. Morphology of the resultant nanofibres were characterised by SEM analysis. Nafion amount in the resultant nanofibres were dependent on the carrier polymer type. The highest concentration of Nafion in the nanofibres was obtained by the electrospinning with PEO. The finest bead-free nanofibres were obtained with PVA. In the second stage the availability of nafion based nanofibres in fuel cells was investigated. The finest nanofibres were obtained with PVA thus it was selected to be the carrier polymer. Because the finer the nanofibres, the better the alignment and the higher the surface area. PVA and PVA/Nafion nanofibres were electrospun. To enhance water stability the membranes were stabilised. Moreover to provide proton conductivity the membranes were sulfonated. Stabilisation and sulfonation were proved by FTIR analysis. Water, methanol and oxidative stability and ion exchange capacity of nanofibres were tested. It was observed that thermally stabilised PVA/Nafion nanofibres have adequate stability and ion exchange capacity was found to be close to those of commercial Nafion® 115 membrane. In conclusion, potential use of thermally stabilised PVA/Nafion nanofibres in fuel cells were revealed.