Passive DMFC system using a proton conductive hydrocarbon membrane Original Research Article

A passive direct methanol fuel cell (DMFC) system was fabricated based on a sulfonated polyimide–silica nanocomposite (SPI–SiO2-1) membrane with high proton conductivity, low methanol (MeOH) permeability, and thin thickness compared to Nafion 117 as a reference sample. The electrochemical performance of the passive systems were highly affected by both MeOH permeation through the membranes and MeOH fuel concentration. Electrochemical performance was improved as the MeOH concentration increased up to 3 M. For high concentrations greater than 5 M MeOH, highly-permeated MeOH led to a severe poisoning on the Pt catalyst surface, which resulted in a rapid reduction in the activation polarization region. SPI–SiO2-1 acted as a better MeOH barrier than Nafion® 117. The maximum power density of a passive DMFC based on SPI–SiO2-1 was 140% greater than Nafion® 117, indicating that SPI–SiO2-1 may be an alternative proton exchange membrane for passive DMFC operated under high MeOH concentrations with high energy density.