Seminars
Lattice-strained Nanoparticle Catalysts for the Electroreduction of Oxygen at PEM Fuel Cell Cathodes
Professor Peter Strasser
Department of Chemical & Biomolecular Engineering
University of Houston
When: Thursday, September 21, 2006
Time: 2:30 PM to 3:30 PM
Where: 1070 Duncall Hall
Abstract:
The cell voltage and performance of Polymer-Electrolyte-Membrane Fuel Cells (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 and characterization of a new structural class of nanoparticle alloy electrocatalysts for use in PEM fuel cell cathodes. The catalysts exhibit promising performance characteristics in terms of their Pt mass based as well as their Pt surface specific activity for the ORR meeting DOE targets for 2010.
Electrochemical Rotating Disk Electrode (RDE) measurements and physico-chemical characterization - including synchrotron X-ray diffraction (XRD) and synchrotron Small Angle X-ray Scattering (SAXS) - show that rapid de-alloying and corrosion processes of base metal rich precursor compounds result in the formation of Pt lattices with unusually high lattice strain. The data suggests that the formation of strained Pt lattices is correlated with the favorable catalytic activity. SAXS results further show how the electrochemical treatment affects the particle size and metal composition distributions of the catalytic particles inside their ionomer-carbon matrix. Our synchrotron studies allow us to formulate relationships between synthetic conditions, structural characteristics and electrochemical activity. Experimental observations are compared to DFT computational predictions as to the impact of strain on the ORR activity of Pt lattices.
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