(511c) Electrospun Particle/Polymer Fiber Mats As Hydrogen/Air Fuel Cell Electrodes

Electrospinning is gaining popularity as a convenient and robust technique for fabricating non-woven mats with sub-micron diameter polymer or particle/polymer fibers. Such mats, with a high activity oxygen reduction reaction catalyst powder and a suitable ionomer binder, can be used as the cathode in proton exchange membrane fuel cells. These nanofiber electrodes provide high interfacial electrode area and sufficient macro and micro porosity for product water removal which are of prime importance. In this talk, a review of recent experimental work on nanofiber mat compositions for hydrogen/air fuel cell cathodes will be presented, where the fibers contain carbon-supported Pt or Pt-alloy powders with perfluorosulfonic acid-based polymer binders. The power output using such a cathode is very high for ultra-low Pt loading. For example, a hydrogen/air fuel cell membrane-electrode-assembly containing a nanofiber TKK PtNi/C catalyst powder cathode and a Pt/C nanofiber anode (where the electrodes were 0.1 mg_Pt/cm², with a blended binder of Nafion^® perfluorosulfonic acid and poly(acrylic acid)) generated 756 mW/cm² at 0.65 V, 80^oC, 100% RH, and 1 atm back pressure. Procedures for fabricating high particle-loaded nanofibers containing platinum-based catalysts and different ionomer binders will be presented. The effects of catalyst type and binder composition on cathode mass activity, electrochemical surface area, cathode durability, and fuel cell power output at high and low relative humidity conditions will be discussed.