Tailored Porosities of the Cathode Layer for Improved Polymer Electrolyte Fuel Cell Performance

Abstract

We show experimentally for the fi rst time that the introduction of macro-pores in the nanoporous catalyst layer of a polymer electrolyte membrane fuel cell can improve its performance. We have ach- ieved a Pt utilization of about 0.23 mg W

1 at 0.6 V which is twice the value of the DOE target for 2020, and three times (0.60 mg W

1 ) smaller than the value of a fully nanoporous reference layer at a catalyst loading of 0.11 mg cm

2 . In this work, monodispersed polystyrene particles with diameters of 0.5 and 1 m m were used as pore formers. Cathode catalyst layers with macroporous volume fractions between 0 and 0.58 were investigated. Maximum performance was observed for fuel cells with a macroporous volume fraction of about 0.52 for a 1 m m thick catalyst layer. The results, which were obtained for the cathode layer, support earlier theoretical predictions that gas access to and water escape from the catalyst can be facilitated by introduction of macropores in the nanoporous layer