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Segmented Pt/Ru, Pt/Ni, and Pt/RuNi Nanorods as Model Bifunctional Catalysts for Methanol Oxidation
Author(s) -
Liu Fang,
Lee Jim Yang,
Zhou Wei Jiang
Publication year - 2006
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.200500253
Subject(s) - bifunctional , catalysis , methanol , nanorod , platinum , materials science , chemical engineering , nuclear chemistry , inorganic chemistry , chemistry , nanotechnology , organic chemistry , engineering
Five‐segment (Pt‐Ru‐Pt‐Ru‐Pt, Pt‐Ni‐Pt‐Ni‐Pt, and Pt‐RuNi‐Pt‐RuNi‐Pt) nanorods with the same overall rod length and the same total Pt segment length were prepared by sequential electrodeposition of the metals into the pores of commercially available anodic aluminum oxide (AAO) membranes. Field‐emission scanning electron microscopy (FESEM) showed that the nanorods were about 210 nm in diameter and about 1.5 μm in length. The alternating Pt and oxophilic metal(s) segments could be easily differentiated in backscattered‐electron images. X‐ray diffraction (XRD) analysis of the nanorods indicated that Pt and Ni were polycrystalline with fcc structures, Ru was hcp, and the co‐deposited RuNi adopted the nickel fcc structure with some negative shifts in the Bragg angles. The chemical states of Pt, Ru, and Ni on the nanorod surface were assayed by X‐ray photoelectron spectroscopy (XPS), and the presence of Pt 0 , Pt II , Pt IV , Ru 0 , Ru VI , Ni 0 , and Ni II was observed. The nanorods were catalytically active for the room‐temperature electrooxidation of methanol in acidic solutions. The relative rates of reaction showed the Pt‐RuNi pair sites as having the lowest overpotential to dissociate water, the highest catalytic activity in methanol oxidation, and the strongest CO‐tolerance in the potential window employed. The use of segmented nanorods with identifiable Pt–oxophilic metal(s) interfaces removes many of the ambiguities in the interpretation of experimental data from conventional alloy catalysts, thereby enabling a direct comparison of the activities of various types of pair sites in methanol oxidation.