Preparation of high-performance polymer electrolyte nanocomposites through nanoscale silica particle dispersion

Abstract

Nano-level dispersion with a minimum amount of non-porous and surface-functionalized nanoparticles is a key to tune physically a common polymer material with poor durability to a powerful material with excellent stability even under harsh fuel cell conditions. Surfactants composed of hydrophobic cores and hydrophilic outer shells are used to assist a homogenous distribution of surface-treated (hydrophilic and hydrophobic) silica nanoparticles. In particular, their effect on nanoparticle dispersion is conspicuous in polymer electrolyte nanocomposites containing hydrophilic surface-treated silica. The hydrophilic silica acts as an additional proton conductor in the acid electrolyte medium, leading to improved proton conductivity without any negative side-effects on the mechanical and chemical durability of the membrane material. The well-distributed hydrophilic silica nanoparticles are beneficial in preventing methanol permeation via compact polymer packing and in strengthening the membrane stability under hot aqueous conditions. Finally, the efficacy of the nano-level dispersion is electrochemically verified in terms of high single-cell performance and further extended life time as a result of a synergistic effect of improved proton conductivity, reduced methanol permeability and excellent hydrolytic durability.