Surfactant-assisted polymer electrolyte nanocomposite membranes for fuel cells

Abstract

Polymer electrolyte nanocomposite membranes were prepared by using a commercial perfluorinated sulfonic acid ionomer (Nafion (R)), nonporous hydrophilic fumed silica (Aerosil 380 (R)), and anionic fluorosurfactant (Zonyl (R) TBS). The fluorosurfactant-containing an acid group, which includes sulfonic acid, contributes to well-dispersion of the silica nanoparticles and simultaneously enhances the proton conductivity of the nanocomposite membrane. Hence, the addition of inorganic fillers such as silica to the fluorosurfactant can significantly improve the properties of the Nafion (R)-based polymer electrolyte nanocomposite membrane. The membranes were characterized in terms of their mechanical properties (e.g., dimensional change and tensile strength) and fundamental electrochemical properties (e.g., proton conductivity and current-voltage (I-V) curve). Zonyl (R) TBS, a commercial anionic fluorosurfactant with sulfonic acid groups at the end of the surfactant chain, added to the Nafion (R) matrix showed improved mechanical and electrochemical properties. The sulfonic acid groups in Zonyl (R) TBS allowed for the additional transport of protons. As a result, the nanocomposite membrane with surfactant exhibited an improved performance. In a single cell test on a proton exchange membrane fuel cell (PEMFC), a membrane electrode assembly (MEA) prepared from the Nafion (R)-silica nanocomposite membrane with TBS exhibited the highest PEMFC performance. The cell was fed with H-2 and O-2 humidified at 75 degrees C for 80 degrees C, respectively at ambient pressure. The current density of this membrane was 1600 mA cm(-2) at 0.6 V and 80 degrees C. superior to 999 mA cm(-2) for Nafion (R) 112.