Effect of nano-size of functionalized silica on overall performance of swelling-filling modified Nafion membrane for direct methanol fuel cell application

A non-destructive swelling-filling (SF) strategy is applied for inorganic modification on Nafion by using functionalized silica (F-silica) nanoparticles as fillers. With the facilely prepared F-silica gel as SF treating agent, the mono-dispersed F-silica nanoparticles can in-situ insert into the Nafion membrane and tightly anchor on the Nafion chains through the hydrogen bonding interaction between the oxygen containing groups on F-silica fillers and –SO3H group on Nafion chains. The F-silica nanoparticles act as bi-functional fillers in the modified Nafion membrane to improve proton conductive and methanol-permeation resistive performances simultaneously. 100% enhanced proton/methanol selectivity therefore leads to a more than 30% improved direct methanol fuel cell (DMFC) performance in terms of power output. By considering the great mechanical, thermal and oxidative stabilities comprehensively, the F-silica-Nafion membranes exhibit promising application potential for high-energy DMFC application.