A novel porous sulfonated poly(ether ether ketone)-based multi-layer composite membrane for proton exchange membrane fuel cell application

An advanced sulfonated poly(ether ether ketone) (sPEEK)-based multi-layer composite membrane with high performance and durability is fabricated, which consists of a porous sPEEK base membrane, two transition layers (TLs) and two PFSA outer layers (PLs). These porous sPEEK base membranes with nanoscale pores are prepared first through a vapor induced phase inversion (VIPI) method. Owing to the higher porosity and the denser distribution of sulfonic acid clusters, the cell performance and physical properties of porous sPEEK membranes are superior to those of sPEEK membranes prepared by a solvent casting method. The multi-layer structure of this composite membrane results in reduced swelling and improved water uptake, and eventually brings about a high proton conductivity. Single cell tests indicate that the multi-layer composite membrane has a higher cell performance and more outstanding durability in comparison with sPEEK membranes. The growth rate of hydrogen crossover current density of this composite membrane is much lower than that of sPEEK membranes, proving the effectiveness of PLs in improving the chemical durability of sPEEK-base membranes. After long-term stability tests, the sPEEK multi-layer composite membrane still shows a good cell performance, especially at low relative humidity (RH).