Effects of SiO₂ nanoparticles incorporated into poly(Arylene ether sulfone ketone) Multiblock copolymer electrolyte membranes on fuel cell performance at low humidity

To improve the performances of fuel cells at low humidity, we have prepared composite electrolyte membranes by incorporating SiO₂ nanoparticles into poly(arylene ether sulfone ketone) (SPESK) membrane. SiO₂ particles were able to be dispersed in SPESK highly uniformly on the nanometer scale by the use of a commercial SiO₂-dimethylacetamide sol. The SiO₂/SPESK cell exhibited improved I-E performance at 53% relative humidity (RH) and 80°C. It was found that such an improvement was due to the reduction of the ohmic resistance and the oxygentransport overpotential at high current densities, probably because the SiO₂nanoparticles promoted the backdiffusion of water generated at the cathode catalyst layer toward the anode. Both the ohmic resistance and the oxygen-transport overpotential were reduced further by using a thin (ca. 12μm) SiO2/SPESK membrane, resulting in remarkably high performances at 53% RH and 30% RH.