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 Nation and CeO2 nanoparticles between the positively charged CeO2 and the negatively charged SO3- end groups of Nation 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 Nation 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 degrees 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 Nation 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 Nation 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 x 10(-4) mV/s, much lower than 11.7 x 10(-4) mV/s of the pristine Nation membrane and 5.78 x 10(-4) mV/s of the Nafion/CeO2 hybrid membrane prepared from the conventional sol-gel method. (C) 2012 Elsevier B.V. All rights reserved.