Comparison of Pd-Co-Au electrocatalysts prepared by conventional borohydride and microemulsion methods for oxygen reduction in fuel cells

Pd-Co-Au/C catalysts synthesized by the conventional borohydride reduction method and reverse microemulsion method followed by heat treatment at 500-900 degrees C in a reducing atmosphere have been characterized by X-ray diffraction. transmission electron microscopy, and polarization measurements for oxygen reduction reaction (ORR) in proton exchange membrane fuels cells. While a single phase Pd-Co-Au alloy is formed at temperatures as low as 500 degrees C with the microemulsion method, heat treatment at 900 degrees C is needed to obtain single phase with the conventional borohydride method. The samples prepared by the microemulsion method show better catalytic activity for ORR compared to those prepared by the conventional borohydride method due to a higher degree of alloying at lower temperatures while keeping the particle size small and the surface area high. The activity of the samples prepared by the microemulsion method is comparable or slightly better than that of commercial Pt/C catalyst at 60 degrees C. (c) 2006 Elsevier B.V. All rights reserved.