Oxygen Reduction Activity and Durability of Ordered and Disordered Pt3Co Alloy Nanoparticle Catalysts at Practical Temperatures of Polymer Electrolyte Fuel Cells

We have succeeded in preparing ordered- and disordered-Pt3Co nanoparticles supported on carbon black (CB), with the nearly identical particle size distribution, by the nanocapsule method with heat-treatment at high temperatures. The temperature dependences of the oxygen reduction reaction (ORR) activities at two kinds of Pt3Co/CB catalysts were examined in O2-saturated 0.1 M HClO4 solution by the multi-channel flow double electrode (M-CFDE) technique. For the ordered-Pt3Co/CB, the apparent rate constant kapp (per unit active area) for the ORR increased with elevation of the temperature up to 65°C and stabilized at nearly the same value as that for commercial c-Pt/CB at 80°C, due to a severe dealloying of the Co component in the hot acid solution. In contrast, the kapp values at the disordered-Pt3Co/CB were higher than those of the ordered-Pt3Co/CB over the whole temperature range from 30°C to 80°C. The disordered-Pt3Co/CB also exhibited higher stability than the ordered-Pt3Co/CB for both an accelerated durability test (ADT, by standard potential step cycles between 0.6 V and 1.0 V) in N2-purged 0.1 M HClO4 solution at 65°C and a corrosion test in air-saturated 0.1 M HClO4 solution at 65°C and 80°C.