Novel proton-conductive nanochannel membranes with modified SiO2 nanospheres for direct methanol fuel cells

A novel approach is proposed to prepare a proton-conductive nanochannel membrane based on polyvinylidene difluoride (PVDF) porous membrane with modified SiO 2 nanospheres. The hydrophilic PVDF porous membrane with a 450-nm inner pore size was chosen as the supporting structure. Pristine SiO 2 with a uniform particle size of 95–110 nm was synthesized and functionalized with –NH 2 and –COOH, respectively. Through-plane channels of porous membrane and arranged functional nanoparticles in pores could contribute to constituting efficient proton transfer channels. The characteristics such as morphology, thermal stability, water uptake, dimensional swelling, proton conductivity and methanol permeability as proton exchange membranes, of the SiO 2 nanospheres, and the composite membrane were investigated. The formation of ionic channels in membrane enhanced the water uptakes and proton conduction abilities of the composite membranes. PVDF/Nafion/SiO 2 –NH 2 exhibited superior proton conductivities (0.21 S cm −1 ) over other samples due to several proton sites and the acid–base pairs formed between –NH 2 and –SO 3 H. Furthermore, all the composite membranes exhibited improved methanol resistance compared with Nafion. Therefore, such a design based on porous membrane provided feasibility for high-performance proton exchange membrane in fuel cell applications.