Nafion®/TiO₂ composite membranes for PEM fuel cells operating at elevated temperature and reduced relative humidity

Our approach for elevating the operational temperature of PEM fuel cells above 100°C is to use inorganic particles inside a composite membrane. Inorganic components tend to enhance water retention at elevated temperatures and can reduce undesirable crossover processes. In this study, we compared the properties of the Nafion®/TiO₂ composite membranes fabricated from Nafion® polymers with different ion exchange capacity (IEC) - 0.91 meq/g and 1.08 meq/g. The main objective was to find a balance between the membrane IEC and the TiO₂ content for optimal fuel cell performance. The membranes were tested for swelling, conductivity, and fuel cell performance under different relative humidity at 120°C. The membranes with IEC of 1.08 meq/g demonstrated better transport properties and much higher performance in a PEMFC. However, excessive swelling of membranes with IEC of 1.08 meq/g caused instability in performance at high current densities and this can be detrimental to membrane durability. copyright The Electrochemical Society.