Preparation of Pt-Nanoparticles-Loaded Carbon Black Catalysts by Using Pt-Carbonyl Cluster Complexes and Their Activity for Oxygen Reduction Reaction

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Pt-carbonyl cluster complexes were prepared just by bubbling CO in various acetonitrile- or ethanol-water mixed solutions containing PtCl62−. They had compositions of [Pt3(CO)3(μ-CO)3]n2− (n=3–6) complexes in which a Pt3(CO)3(μ-CO)3 unit composed of triangular Pt atoms and two types of CO ligands was stacked. The number of Pt3(CO)3(μ-CO)3 units tended to decrease as water content in the mixed solutions increased. Pt nanoparticles prepared from the Pt-carbonyl cluster complexes had much smaller mean particle size (1.8–2.0 nm) and narrower size distribution (ca. 0.3 nm) than commercial ones. The Pt nanoparticles-loaded carbon black (Pt/CB) catalysts improved mass activity at 0.9 V for oxygen reduction reaction compared to the commercial catalyst (Pt/CBTKK). In particular, the mass activity for Pt/CB prepared from the [Pt3(CO)3(μ-CO)3]52− complex produced in a water-ethanol mixed solution (water content: 50 vol.%) was ca. 1.7 times higher than that of the Pt/CB-TKK.