Controlled synthesis of Pt nanoparticles via seeding growth and their shape-dependent catalytic activity.

Through a seed-mediated growth route, Pt nanoparticles (NPs) with tunable shape and size were prepared, such as octahedral, cuboctahedral, branched and rice-like. Three nanometer Pt NPs were prepared and dispersed in oleyl amine to form seed solution and then Pt precursor (platinum acetylacetonate (Pt(acac)(2))) was added. Under high temperature, oleyl amine as both reducing and protective agents can reduce Pt precursor to Pt atoms which selectively deposit on seeds surface to form variously structured Pt NPs. By adjusting the reactive conditions (the molar ratio of Pt metals from Pt(acac)(2) and seed (PPS), the seed diameter, the addition route of Pt(acac)(2)), the NPs growth could be controlled to fall into kinetic or thermodynamic regime, producing variously shaped NPs. On the basis of observed results, a reaction mechanism in which the resulting NP shape had strong dependence on c/s (c=precursor concentration, s=available deposition surface area) was figured out. The obtained NPs were supported on black carbon to act as Pt/C catalysts for oxidization of methanol and results show that the catalysts from branched NPs had higher catalytic activity and stability than ones from polyhedral NPs.