Investigation of Nafion based composite membranes on the performance of DMFCs

In this study, Direct Methanol Fuel Cells (DMFCs) based on composite membranes (Nafion/SiO2 and Nafion/TiO2) were manufactured; and their performances were compared with that of the DMFC based on Nafion® 115 membrane. For this purpose, composite membranes were synthesized applying the recasting method with the inorganic particle loading of 2.5 wt%. The structures of these composite membranes were investigated by Scanning Electron Microscopy (SEM), proton conductivity measurement and water uptake measurement. Ultrasonic coating technique was used in the manufacturing of the Membrane Electrode Assemblies (MEAs). The performance tests of the composite membranes were conducted using in-house experiments. In these tests, the effect of methanol concentration (0.75, 1, and 1.5 M) on the performance of the MEA having Nafion® 115 was investigated at 80 °C to find the value of the methanol concentration that yields the highest power density. This study showed that the MEA operating at 1 M gives the highest performance. Then, the performance of this MEA was compared with that of the MEAs having Nafion/SiO2 and Nafion/TiO2 composite membranes in single cell DMFC setup at 60 °C, 80 °C, and 95 °C. The results of these experiments demonstrated that the MEA having Nafion/TiO2 composite membrane provides much better performance with the maximum power density values of 422.04 W/m2, 641.16 W/m2, and 710.88 W/m2 at 60 °C, 80 °C, and 95 °C, respectively.