Methanol crossover reduction by Nafion modification with palladium composite nanoparticles: Application to direct methanol fuel cells

Modified Nafion membranes by self-assembling of palladium composite nanoparticles were successfully synthesized and used for the reduction of methanol crossover in Direct Methanol Fuel Cells (DMFC). The positively charged polydiallyldimethylammonium (PDDA) was used for stabilizing the palladium nanoparticles. Modified and unmodified membranes were tested in a DMFC at 30 °C and 50 °C. The performance of the DMFC using modified membranes with different composite nanoparticles (i.e., Pd/PDAA ratios) and self-assembling times was compared with that using an unmodified membrane. The modified Nafion membranes proved to reduce the methanol crossover in ca. 10% – 35%, depending on the self-assembling time, nanoparticles composition and test temperature. However, a decrease in the performance was observed mainly for the modified membrane with the higher PDDA content due to a decrease in the proton conductivity. On the other hand, the membrane modified with nanoparticles containing less PDDA and tested at 50 °C showed similar performance as the unmodified one. Additionally, the fuel cell efficiencies obtained for all the modified membranes at both temperatures were similar or higher than the unmodified one.