Multisegment PtRu Nanorods: Electrocatalysts with Adjustable Bimetallic Pair Sites


  • The authors are indebted to Prof. E. T. Kang and Q.-J. Cai for their assistance with physical vapor deposition. F. Liu acknowledges the National University of Singapore for her research scholarship.


Multisegment PtRu nanorods (Pt–Ru, Pt–Ru–Pt, Pt–Ru–Pt–Ru, Pt–Ru–Pt–Ru–Pt, Pt–Ru–Pt–Ru–Pt–Ru) with customizable lengths of the individual metals are obtained by the sequential electrodeposition of the metals into the pores of anodic aluminum oxide (AAO) membranes. Field-emission scanning electron microscopy (FESEM) shows that the nanorods are about 200 nm in diameter and 1.2 μm long, with 900 nm of total platinum-segment length. The alternating platinum and ruthenium segments can be easily differentiated using FESEM. X-ray diffractometry reveals that the platinum and ruthenium in the bimetallic nanorods are polycrystalline with face-centered cubic and hexagonal close-packed crystal lattice structures, respectively. The presence of Pt0, PtII, PtIV, Ru0, and RuVI on the surface of the bimetallic nanorods is demonstrated via X-ray photoelectron spectroscopy. The nanorods are catalytically active in the room-temperature electro-oxidation of methanol. The relative rates of reaction, recorded using chronoamperometry, show a linear relationship between the long-time (near-steady-state) current density and the number of Pt–Ru interfaces. The use of segmented nanorods with a controlled number of Pt–Ru interfaces removes many of the ambiguities in the interpretation of experimental data from conventional alloy catalysts and has provided a direct demonstration of the role of pair sites in bifunctional catalysis.