Synthesis of Nafion/CeO2 hybrid for chemically durable proton exchange membrane of fuel cell

Nafion/CeO2 hybrid composites prepared through a self-assemble route are proposed for chemically durable electrolyte membrane of fuel cell. Self-assembly of Nafion and CeO2 nanoparticles between the positively charged CeO2 and the negatively charged SO3− end groups of Nafion ionomers gives the composite structure a good compatibility on the interface. As a result, the Nafion/CeO2 hybrid proton exchange membranes present conductivities slightly lower than that of the pristine Nafion membrane at 100 RH% condition, whereas much higher than the later when humidification is below 75 RH%. The Nafion/CeO2 hybrid membranes also display excellent radical scavenge ability under hydroxyl radical corrosion condition. With Fenton reagent of 30 wt% H2O2 solution containing 20 ppm FeCl2 at 85 °C, the fluoride emission rates for the self-assembled Nafion/CeO2 membranes with ceria content of 1, 3, 5, 10 wt% are 43.05, 8.67, 6.01, 4.47 mg h−1, respectively, much lower than that for pristine Nafion membrane (55.78 mg h−1) and Nafion/CeO2 membrane prepared from the conventional sol–gel method (11.64 mg h−1). Another important aspect of the self-assembled Nafion/CeO2 membrane contributed to the durability is the low humidity-induced stress and dimensional stability. The humidity-induced stress of the self-assembled Nafion/CeO2 membranes with ceria content of 1–10 wt% was 1.22–1.93 MPa, in comparison to 2.25 MPa of pristine Nafion membrane. Thus, the proton exchange membranes prepared from self-assembled Nafion/CeO2 present high durability under the fuel cell operating conditions. In the open circuit voltage accelerated test under in situ accelerating RH cyclic test, the OCV reduction rate of self-assembled Nafion/CeO2 membrane with ceria content of 5 wt% is 1.13×10−4 mV/s, much lower than 11.7×10−4 mV/s of the pristine Nafion membrane and 5.78×10−4 mV/s of the Nafion/CeO2 hybrid membrane prepared from the conventional sol–gel method.