(671b) Lattice-Strained Pt Shell Nanoparticle Catalysts

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.