Preparation and Characterization of Pt-Ru Bimetallic Catalysts Synthesized by Electroless Deposition Methods

Two series of Pt@Ru/C and Ru@Pt/C bimetallic catalysts have been prepared by an electroless deposition (ED) method. For Pt@Ru/C compositions, a new ED bath was developed using Ru(NH3)(6)Cl-3 as the Ru precursor and HCOOH as the reducing agent. For Ru@Pt/C preparations, a standard bath using H2PtCl6 and DMAB as the Pt precursor and reducing agent, respectively, was employed. The Pt@Ru/C and Ru@Pt/C bimetallic catalysts have been characterized by temperature-programmed reduction (TPR), selective chemisorption, X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM) with X-ray energy dispersive spectroscopy (XEDS). TPR and selective chemisorption (H-2 titration of oxygen-precovered surfaces) experiments have confirmed the existence of strong surface interactions between Pt and Ru, as evidenced by hydrogen spillover of Pt to Ru (Pt-assisted reduction of oxygen precovered Ru). XPS analyses also showed e(-) transfer from Pt to Ru on the bimetallic surface, again indicating strong surface interactions between Pt and Ru. Finally, the STEM images and XEDS elemental maps provided strong visual evidence of targeted deposition of the secondary metal on the primary metal. The elemental maps confirmed that individual nanoparticles of both Pt@Ru/C and Ru@Pt/C catalysts prepared by ED were bimetallic, with excellent association between the primary and the secondary metals.