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

Pt-carbonyl cluster complexes were prepared just by bubbling CO in various acetonitrile- or ethanol-water mixed solutions containing PtCl62-. They had compositions of [Pt-3(CO)(3)(mu-CO)(3)](n)(2-) (n = 3-6) complexes in which a Pt-3(CO)(3)(mu-CO)(3) unit composed of triangular Pt atoms and two types of CO ligands was stacked. The number of Pt-3(CO)(3)(mu-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/CB-TKK). In particular, the mass activity for Pt/CB prepared from the [Pt-3(CO)(3)(mu-CO)(3)](5)(2-) 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.