Nafion® and nano-size TiO2–SO42− solid superacid composite membrane for direct methanol fuel cell

TiO2–SO42− solid superacid nanoparticles were fabricated by sol–gel reaction, sulfation and calcination procedure. The TiO2–SO42−/Nafion® composite membranes were prepared via solution casting. The physico-chemical properties of solid superacid nanoparticles were investigated by thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The water uptake, proton conductivity, and methanol permeability of composite membranes were evaluated. The proton conductivity of the composite membranes shows slightly lower than that of pure recast Nafion® membrane. The composite membranes with lower TiO2–SO42− contents (3, 6%) reduced the methanol crossover, while the membrane with higher contents did not show any ability to decrease the methanol crossover. In direct methanol fuel cell (DMFC) single cell performance test, the composite membrane with 6% TiO2–SO42− content achieved similar performance at 1 M methanol feed, and a higher performance at 5 M methanol feed compared with pure recast Nafion® membrane.