Enhanced Activities for the Oxygen Reduction Reaction at Pt-Skin Layers on Pt-Co Alloy Single-Crystal Electrodes

摘要

The kinetically-controlled current densities, j_k for the oxygen reduction reaction (ORR) were evaluated at Pt skin layers formed on Pt_(100-x)Co_x(111) single-crystal electrodes in air-saturated 0.1 M HClO_4 solution as a function of Co content, x atom%, by use of the rotating disk electrode method. We found a maximum j_k value as high as 3.0 mA cm~(-2) at 0.9 V vs. RHE on the Pt skin/Pt_(75)Co_(25)(111) electrode, which is more than 20 times higher than that on the Pt(111) electrode. The enhanced ORR activities of Pt-skin/Pt-Co(111) electrodes cannot be explained on the basis of decreased "OH poisoning," because the surface oxidation charge densities up to 0.9 V in N_2-purged solution were nearly constant, irrespective of Co content.