title: One-step sonochemical syntheses of Ni@Pt core-shell nanoparticles with controlled shape and shell thickness for fuel cell electrocatalyst.
abstract: We demonstrate a facile one-step method to synthesize Ni@Pt core-shell nanoparticles (NPs) with a control over the shape and the Pt-shell thickness of the NPs. By adjusting the relative reactivity of the Pt and Ni reagents in ultrasound-assisted polyol reactions, two Ni@Pt NP samples of the same composition (Ni/Pt=1) and size (3-4 nm) but with different particle shape (octahedral vs. truncated octahedral) and different Pt-shell thicknesses (1-2 vs. 2-3 monolayer) are obtained. The control is achieved by using different Ni reagents, Ni(acac)2 (acac=acetylacetonate) and Ni(hfac)2 (hfac=hexafluoroacetylacetonate). A reaction mechanism that can explain all of the observations is proposed. The Ni@Pt NPs show up to threefold higher mass activity than pure Pt NPs in oxygen reduction reaction. Between the two Ni@Pt NP samples, the one composed of octahedral NPs with the thicker Pt-shell has higher activity than the other.
authors.affiliation: SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors.forename: Eunjik
authors.initials: E
authors.lastname: Lee
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Jang
authors.forename: Md Abdul
authors.initials: MA
authors.lastname: Matin
authors.forename: Young-Uk
authors.initials: YU
authors.lastname: Kwon
keywords: Core–shell nanoparticles; Electrocatalysis; Fuel cells; Oxygen reduction reaction; Sonochemistry