PREPARATION AND CHARACTERIZATION OF POLYMER/PARTICLE ELECTROSPUN FIBER ELECTRODES FOR HYDROGEN/AIR FUEL CELLS

Abstract

Hydrogen/air fuel cells are a clean-energy alternative to the internal combustion engine in automotive vehicles. This type of fuel cell utilizes the chemical potential between hydrogen and oxygen to generate electricity, with water as the by-product. A significant barrier to largescale commercialization of fuel cell electric vehicles is the costly platinum catalyst needed to facilitate the electrochemical reaction. Herein, we discuss the use of electrospinning particle/polymer fibers to produce highly porous fuel cell electrodes with a high surfac e area. These fibrous electrodes increase platinum availability and are appreciably more resistant to degradation than conventional spray electrodes. Specifically, this work discusses: (1) Improved power production using a platinum-nickel alloyed cathode catalyst, which is inherently more active towards the oxygen reduction reaction than pure platinum. PtNi/C fiber cathodes membrane-electrode-assemblies (MEAs) exhibited high power at both high and low operating humidity and retainedg0% of beginning-of-life power after 30,000 load cycles. (2) The production of fiber electrodes with a neat Nafion binder. This was achieved by spinning with Na*-form Nafion and poly(ethylene oxide), the latter of which was removed via awater wash. Neat-Nafion fiber MEAs exhibited increased power output and, surprisingly, significantly improved performance at low operating humidity due to capillary condensation of water in small pores. (3) The use of higher platinum loading cathodes in fiber mat MEAs for heavy duty vehicle applications. By altering the electrode processing, high cathode loadings lead to improve power and durability. (4) Examination of water distribution profiles in an operating fuel cell MEA via neutron scattering experiments with both spray and fiber mat electrodes. It was confirmed that, at high operating humidity, fiber electrode MEAs held less water than spray electrode MEAs.