Multi-segment Pt-RuNi nanorods for methanol electro-oxidation at room temperature

Three five-segment Pt-RuNi-Pt-RuNi-Pt nanorods with the same diamete, same overall rod length, and same total Pt segment length differing only in RuNi compositions, were prepared by sequential electrodeposition of Pt and RuNi (co-deposited with different Ru to Ni ratios) into the pores of commercially available anodic aluminum oxide membranes. The alternating Pt and RuNi segments could be easily differentiated in backscattered electron images from scanning electron microscopy. X-ray diffraction indicated that Pt was polycrystalline with face-centered cubic (fcc) structure; while co-deposited RuNi adopted either the Ru hexagonal close-packed (hcp) structure or the Ni fcc structure depending on the Ni content. X-ray photoelectron spectroscopic analysis showed that Pt(0) was the major surface oxidation state for Pt in the Pt segments, while Ru(0) and NiO dominated on the surface of the RuNi segments. The segmented nanorods were catalytically active in the room-temperature electro-oxidation of methanol in acidic solutions. Among the nanorods tested, the relative rates of reaction as measured by cyclic voltammetry and chronoamperometry showed that the Pt-RuNi pair sites with the Ru:Ni mass ratio of 4.24:1 had the highest catalytic activity and strongest CO-tolerance in the potential window investigated. The Pt-RuNi pair sites were also more active than the similarly produced Pt-Ru and Pt-Ni pair sites reported in a previous publication [F. Liu, J. Y. Lee, and W. J. Zhou, Small, 2, 121 (2006)]. (c) 2006 The Electrochemical Society.