New palladium alloys catalyst for the oxygen reduction reaction in an acid medium

Extremely active palladium-based alloys catalysts without platinum for the oxygen reduction reaction (ORR) in an acid medium were shown for the first time. The palladium alloys were prepared by sputtering under a vacuum of less than 10(-4) Pa from a palladium target and an alloying metal sheets on a glassy carbon support. Their electrochemical characteristics for ORR were determined at 30 degreesC in sulphuric acid. It was demonstrated that the base voltammograms (CVs) of Pd-Co alloys did not show significant change in the shape or size during the whole measurements procedure. Furthermore the Pd-Co alloy CV were found to be completely different from those of Pd and Co alone and they never changed to become more I'd-like or Co-like. The Pd-Co alloy catalysts are stable under the applied experimental conditions. The interesting properties of the alloys for the ORR were attributed to an appropriate electronic stabilisation of the alloying element atom in the alloy which may prevent its corrosion and which allows the enhancement of its catalytic activity. It was further demonstrated that an improvement of at least 250 mV, based only on a theoretical estimation from Tafel slope, in ORR over-voltage could be obtained if a Pd-Co 28% catalyst is used at 30 degreesC instead of Pt for PEFC or acid Solid Polymer Electrolyser Applications. (C) 2003 Elsevier B.V. All rights reserved.