CO stripping as an electrochemical tool for characterization of Ru@Pt core-shell catalysts

The paper reports an application of CO stripping-voltammetry as a diagnostic tool for the determination of surface composition of various PtRu nanoparticles (NPs). A series of electrochemical experiments on different systems, including monometallic Pt and Ru, a commercially available PtRu alloy, Ru@Pt (Ru NPs covered by a Pt shell), and their physical mixtures verified that the surface of the Ru@Pt particles does not contain significant amounts of ruthenium. A large cathodic shift (200 mV) of the main CO stripping peak of the Ru@Pt with respect to that of Pt was observed, consistent with what has been found at other catalysts with a Pt skin but of a different architecture. An additional small separate stripping peak at a potential corresponding to the oxidation of adsorbed CO at Pt/C is interpreted as being due to either separate Pt particles in the catalyst or thick Pt shells at a minor fraction of the Ru@Pt particles. Since the method probes the whole sample it will be useful for assessment of catalyst homogeneity. (C) 2011 Elsevier B.V. All rights reserved.