Vertically Oriented Polymer Electrolyte Nanofiber Catalyst Support for Thin Film Proton-Exchange Membrane Fuel Cell Electrodes

Polymer electrolyte fuel cells are highly efficient and offer high power density, but high precious-metal loading and degradation of carbon-supported platinum (Pt) catalysts still hinder commercialization. Ionomer binders in conventional electrodes also introduce undesirable, high oxygen-transport resistance. This paper presents an alternative composite Nafion nanofiber catalyst support electrode, in which the nanofibers provide robust internal proton transport to a conformal Pt catalyst coating without impeding O-2 transport. The high-surface-area electrodes are prepared by solution casting ionomer onto a sacrificial template to simultaneously fabricate the nanofibers and the membrane. Thin Pt films are deposited on the nanofibers using either physical vapor deposition or chemical vapor deposition. The electrochemical characterization of the nanofiber electrodes demonstrates the high current density and specific activity of this nanofiber approach relative to prior electrodes fabricated by depositing Pt directly onto other Nafion surfaces.