| Abstract
| - A combined theoretical and experimental analysis of the electrode potential dependencies of activation energiesis presented for the first step in oxygen reduction over platinum and platinum alloy catalysts in bothpolycrystalline and carbon supported form. Tafel data for several of the catalysts are used to predict potential-dependent activation energies for oxygen reduction over the 0.6−0.9 V range in strong and weak acid.Comparisons with the theoretical curve show good agreement above 0.8 V, suggesting a fairly constantpreexponential factor. Arrhenius determinations of activation energies over the 0.7−0.9 V range yield littletrend for weak acid, possibly because of the larger uncertainties in the Arrhenius fits, but the strong acidresults have smaller uncertainties and for them the measured activation energies trend up with potential.
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