High Performance Fuel Cell Membrane By Electric Poling of Poly (ether sulfone)/Sulfonated Poly(ether ether ketone) Composite

Abstract

Traditional fuel cell membrane suffers from fuel cross over and high degree of swelling after extensive operation. To circumvent these deficiencies, we disclose in this study proton conducting membrane by incorporating poly(ether sulfones)(PES) with sulfonated poly(ether ether ketone)(sPEEK, degree of sulfonation=50%) prepared under electric field poling condition. The external field enhanced the aromatic chain ordering from both sPEEK and PES and improved the miscibility. This external force is conducive to the formation of more densely packed and ordered hydrophobic domain that eventually leads to long range ordered hydrophilic proton conducting channels. The averaged hydrophilic dimension is smaller than that in generic sPEEK, thus displayed much lower methanol permeability (3.17x10-7 cm2/s), and lower swelling ratio (31.20%). However, the conductivity (7.43x10-2 S/cm) is higher compared to sPEEK at 64% degree of sulfonation, and comporable with Nafion. The binary composite is highly durable; and shows improved membrane mechanical strength, possibly due to the densification of amorphous domain. Nearly 50% increase of DMFC power output is observed using this membrane, and the best power density is recorded at 150mA/cm2 (80 oC, 1M Methanol).