Core Size-Dependent Proton Conductivity of Silica Filler-Functionalized Polymer Electrolyte Membrane

Abstract

Polymer electrolyte fuel cells (PEFC) are expected as next energy generation systems, and their performance is strongly dependent upon the polymer electrolyte membrane (PEM). We have suggested a new model of PEM with a three-dimensional proton conduction passways structure using the filler method, particularly focused on the functionalization of filler particles. The polymer surface-functionalized silica nanoparticles (NPs) with three different particle sizes were prepared by the reversible addition–fragmentation chain transfer polymerization with particles (RAFT PwP) method that we developed. Silica NPs coated with an in situ polymerized block copolymer consisted of a proton conductive polymer and a protective polymer. We confirmed that the proton conductivity increased and the activation energy decreased as the core particle size became smaller because of enlarging the total interface area between each particle and increasing the proton conduction passways.