Antioxidant proton conductive toughening agent for the hydrocarbon based proton exchange polymer membrane for enhanced cell performance and durability in fuel cell

The antioxidant toughening agent for the hydrocarbon based proton exchange polymer electrolyte membranes, cerium/organosiloxane polymer network (Ce/OSPN), is synthesized via sol-gel reaction. Ce/OSPN is introduced to the sulfonated poly(ether ether ketone) (SPEEK), a typical hydrocarbon type polymer electrolyte membrane, by formation of a semi-interpenetrating polymer network (semi-IPN) structure. As Ce/OSPN possesses superior properties to SPEEK in mechanical flexibility, proton conductivity, and oxidation stability than SPEEK, it resolves 3 inherent drawbacks of the pristine SPEEK membrane including (i) brittleness, (ii) low proton conductivity, and (iii) poor durability. Addition of 20 wt% Ce/OSPN (at Ce/silicon mol ratio = 0.10) enhances the elongation at break of the SPEEK membrane about twice. The power density of the MEA fabricated with the semi-IPN membrane is 208 mW cm−2, which is much higher than that of the pristine SPEEK membrane, 165 mW cm−2. The power density loss of the same semi-IPN membranes as determined by the Fenton's test is 4.8%, whereas those of pristine and semi-IPN membrane without cerium are 33.9% and 34.0%, respectively. This Ce/OSPN agent is expected to be applied to a variety of hydrocarbon based polymer electrolyte membranes.