Low methanol permeable and high proton-conducting Nafion/calcium phosphate composite membrane for DMFC

Calcium phosphate (CP)/Nafion composite membranes were fabricated by incorporating CP into Nafion structure for the direct methanol fuel cells (DMFCs). This composite membrane showed lower methanol crossover compared to cast Nafion and Nafion® 117. This is likely to be due to high crystallinity and low water uptake content in the composite membranes. In addition, the composite membranes containing CP2.5% and CP5% showed higher proton conductivity than cast Nafion from 50 to 100 °C. In relation to high proton conductivity, the absorption vibration at 2360 cm−1 corresponding to sulfonic acid bridge represents high thermal stability in the composite membranes even at high temperature. Focused ion beam (FIB) micrograph displays well-developed three-dimensional channels in the surface and cross-section area within the composite membrane, allowing the various conducting paths and high conductivity.