Lattice-strained Pt shell nanoparticle catalysts for the electroreduction of oxygen at PEMFC cathodes

FUEL 221

Peter Strasser, and Shirlaine Koh. Department of Chemical Engineering, University of Houston, Houston, TX 77204
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. Preliminary results 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.