Modified Polyaniline-Nafion-Silica Nanocomposites for DMFC

Among the different fuel cell technologies, the direct methanol fuel cell (DMFC), with methanol as the energy carrier, has one of the best application prospects as an energy converter for portable electronic devices and environmentally benign vehicles. Currently Nafion® (poly-perfluorosulphonic acid) membranes are used as solid electrolytes in DMFC applications due to their excellent chemical stability and ionic conductivity. However, these membranes suffer from methanol crossover (diffusion of the methanol from anode to cathode through the polymer electrolyte membrane). Methanol crossover has a severe negative impact on the overall performance of the DMFC due to a reduction in fuel efficiency through wasted oxidation at the cathode, as well as catalyst poisoning. Indirect approaches, such as the use of diluted methanol as a fuel and low operation temperatures, have been used in order to reduce the methanol crossover but have failed in obtaining significant fuel cell improvements. Recent studies have shown that the structural modification of Nafion® membranes can lead to considerable reduction in methanol crossover but also result in an undesirable reduction of proton conductivity, both key factors in determining overall fuel cell performance. In previous studies the addition of polyaniline to a fuel cell electrode has shown an increase in catalytic activity of methanol electro-oxidation. This study aims at modifying Nafion® and Silica-Nafion membranes with polyaniline, an electron conductive polymer, in order to modify the membrane structure to reduce the methanol cross-over.