Characterization of sulfonated poly(ether ether ketone)/polytetrafluoroethylene composite membranes for fuel cell applications

The sulfonated poly(ether ether ketone) (SPEEK) / polytetrafluoroethylene (PTFE) composite membranes were produced to aid the swelling properties. The PTFE porous films were used as reinforcing material for the SPEEK/PTFE composite membranes. Scanning electron micrographs showed that SPEEK resin was distributed uniformly in the composite membrane and completely plugged the micropores; there is a continuous thin SPEEK film present on the PTFE surface. The dimensional stability and mechanical strength of the composite membranes were apparently improved. The composite membrane had a smaller oxygen permeability than the Nafion (R) membrane despite it being larger than that of the SPEEK homogenous membrane. The performance and stability of the PEMFC with SPEEK/PTFE composite membranes were also tested. Results showed that the fuel cell had a larger resistance than the SPEEK homogenous membrane or the Nafion (R) membrane, but these disadvantages are compensated for with the thinner composite membrane, because of its low gas permeability and high mechanical strength. Stability testing showed that the cell performance could be kept steady for more than 150 hours. The structure of the composite membrane didn't undergo any change and a tight bond remained between the composite membrane and the catalyst layers of electrode after more than 300 hours of intermittent operation.