The cell voltage and performance of Hydrogen Polymer-Electrolyte-Membrane Fuel Cells (H-PEMFCs) deviate strongly from their theoretical values due to severe kinetic overpotentials at the oxygen/air cathode. The overpotentials are a manifestation of the sluggish rate of adsorption and reduction of molecular oxygen on Pt cathode electrocatalysts. The identification of more active, cost-effective and corrosion stable electrocatalysts for the oxygen reduction reaction (ORR) therefore continues to be a scientific priority in Fuel Cell catalysis research.
We report the synthesis, characterization and mechanistic investigation of a new Pt alloy electrocatalyst systems for use in PEM fuel cell cathodes. The catalysts exhibit remarkable performance characteristics in terms of their Pt mass based as well as their Pt-surface specific activity for the ORR meeting and exceeding the DOE activity targets of 2010 of 0.44 A/mg Pt and 720 uA/cm2.
Catalyst characterization before and after catalysis indicate that rapid de-alloying processes of Pt-poor precursor compounds result in the formation of highly active lattice-strained (lattice-compressed) Pt shell nanoparticles. Experimental observations are compared to computational predictions as to the impact of lattice strain on ORR activity of Pt.