Silica Nafion Modified Composite Membranes for Direct Methanol Fuel Cells

Direct Methanol Fuel Cells (DMFCs) operate by electro‐oxidation of methanol and the transport of the protons by means of a polymer electrolyte membrane. Current systems employ Nafion (perjluorosulphonic acid) membranes as the transport media for the protons, which experience a high methanol crossover reducing the efficiency by the oxygen reduction reaction at the anode side of the fuel cell. This work investigated the microstructural modification of Nafion membranes with silica nanoparticles. It was shown that this mod4cation led to reduced methanol crossover, whilst methanol permeability was slightly reduced without compromising the conductivity at the normal DMFC operation temperature (75‐80°C). Methanol uptake was reduced by 55% with the incorporation of the silica nanoparticles into the Nafion matrix. In addition, pure methanol uptake appeared to be less effective than methanol mixtures. These results indicated the presence of water assisted methanol permeation as the hydrophilic sulphonic group and the hydrophobic polymeric backbone of Nafion were sensitive to methanol solvation.