The oxygen reduction reaction (ORR) is the major source of overpotential loss in low-temperature fuel cells.  Expensive, Pt-based materials have been found to be the most effective catalysts, but exploration of alternatives has been hampered by stability constraints at the typical operating conditions of low pH and high potential.  Many metals exhibit enhanced corrosion stability at high pH, and recent advances in alkaline membrane technology have made fuel cell operation at high pH feasible.  In basic medium, Ag is redox stable and shows comparable ORR activity to Pt on a power-per-dollar basis.  In this study we probe the elementary mechanism of oxygen reduction on Pt and Ag with microkinetic modeling and quantum chemical calculations, which provide insights that point to superior ORR activity for various alloys of Ag. Though these alloys are not favored to form thermodynamically, we utilize novel synthesis techniques to generate the desired structures, and they are stable under operating conditions.  We demonstrate the superior ORR activity with rotating disk electrode experiments, and perform thorough structural characterization of the bulk and surface properties with a combination of cyclic voltammetry, x-ray diffraction, and electron microscopy with spatially resolved energy-dispersive x-ray spectroscopy and electron energy loss spectroscopy.Holewinski and Linic. J. Electrochem. Soc. 159,(2012).

Kinetic analysis of electrochemical oxygen reduction and development of Ag-alloy catalysts for low temperature fuel cells

246th National Meeting (2013)

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