Bimetallic Ru-Pt and Pt-Co Fuel Cell Catalysts Prepared By Strong Electrostatic Adsorption and Electroless Deposition

The methods of Strong Electrostatic Adsorption (SEA), and its incipient wetness analog, Charge Enhanced Dry Impregnation (CEDI), have been shown to yield supported metal nanoparticle catalysts with high dispersion and narrow size distribution. Catalysts prepared by SEA and CEDI therefore are desirable as seeds for addition of secondary metal using Electroless Deposition (ED), as the prepared bimetallic catalysts should be of similar dispersion as the base catalyst. This study demonstrated the use of these methods to prepare two series of carbon supported bimetallic catalysts containing Pt which were then characterized and evaluated with cyclic voltammetry. The first system used Pt as the base metal, prepared by SEA on XC72R carbon, with Ru as the secondary metal added by ED (Pt@Ru/C). The second system used Co as base metal, prepared by a modified CEDI method on Carbon Black, with Pt added by ED (Pt-Co/C)

XRD, HAADF-STEM, and XEDS characterization showed that the Pt@Ru/C catalysts did not have alloying of the component metals and that the catalysts have bimetallic surface composition. The resulting Pt-Co/C catalysts had particles with irregular morphology that were larger than the seed Co particles. These were determined to have thin alloyed Pt-Co phases and domains of pure Pt. Evaluation of these catalysts showed higher mass activities, with respect to platinum content, compared to commercially available monometallic and bimetallic catalysts. This enhancement in performance is associated with the electronic interaction between Pt and Ru on the catalyst surface and the lattice contraction for Pt-Co alloys.