Electrocatalytic activity for oxygen reduction reaction of Pt nanoparticle catalysts with narrow size distribution prepared from [Pt3(CO)3(μ-CO)3]n2- (n = 3–8) complexes

Various Pt-carbonyl cluster complexes ([Pt3(CO)3(μ-CO)3]n2- (n = 3–8)) were prepared by simply bubbling CO through PtCl62- solutions with different solvents. The number of layered Pt3(CO)3(μ-CO)3 units (n) was independent of water content and the length of the alkyl chain of the solvent, but it increased with a decrease in the permittivity of the solvent. The Pt-carbonyl cluster complexes were applied to the preparation of Pt-nanoparticle-loaded carbon black (Pt/CB). The mean size of the resultant Pt nanoparticles increased with n, whereas their size distribution remained narrow (±0.3 nm) irrespective of n. For the oxygen reduction reaction, the specific activity (SA) of each Pt/CB catalyst was almost equivalent to that of the Pt/CB catalyst produced by Tanaka Kikinzoku Kogyo (Pt/CB-TKK). Meanwhile, the mass activity (MA), the product of SA and real specific surface area (SSAreal), at 0.9 V of each Pt/CB catalyst was superior to that of Pt/CB-TKK because the SSAreal evaluated experimentally for the Pt/CB catalysts was higher than that for the Pt/CB-TKK. In particular, the MA at 0.9 V of the Pt/CB catalyst (Pt-et(50)/CB) prepared from [Pt3(CO)3(μ-CO)3]52- synthesized in ethanol–water (50:50 v/v) was about 1.7 and 2.0 times higher than those of commercial Pt/CB-TKK and E-TEK catalysts, respectively.

► [Pt3(CO)3(μ-CO)3]n2- (n = 3–8) can be prepared in solvents with different permittivity. ► The number of layers of the prepared complexes increases as permittivity decreased. ► The mean size of Pt nanoparticles loaded on CB depended on number of layers. ► The size distribution remains narrow (±0.3 nm) irrespective of number of layers. ► Mass activity of Pt-et(50)/CB is higher than that of the commercial Pt/CB catalysts.