Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

A single layer, bi-metallic RuPt catalyst on Au(111) is synthesized using surface limited red-ox replacement of underpotentially deposited Cu and Pb monolayers though a two-step process. The resulting 2D RuPt monolayer nanoclusters have a unique core-edge structure with a Ru core and Pt at the edge along the perimeter. The activity of this catalyst is evaluated using CO monolayer oxidation as the probe reaction. Cyclic voltammetry demonstrates that the 2D RuPt core-edge catalyst morphology is significantly more active than either Pt or Ru monolayer catalysts. Density functional theory calculations in combination with infra-red spectroscopy data point towards oscillating variations (ripples) in the adsorption energy landscape along the radial direction of the Ru core as the origin of the observed behavior. Both, CO and OH experience a thermodynamic driving force for surface migration towards the Ru-Pt interface, where they adsorb most strongly and react rapidly. We propose that the complex interplay between epitaxial strain, ligand and finite size effects is responsible for the formation of the rippled RuPt monolayer cluster, which provides optimal conditions for a quasi-ideal bi-functional mechanism for CO oxidation, in which CO is adsorbed mainly on Pt, and Ru provides OH to the active Pt-Ru interface. [Display omitted] •A novel, single layer 2D RuPt core-edge catalyst was synthesized.•The 2D RuPt core-edge catalyst shows superior CO electro-oxidation activity.•Finite size effects lead to the formation of a compressed and rippled nanocluster.•The rippled surface has a rich adsorption behavior with anisotropic diffusion properties in the radial and azimuthal direction.•A mechanism consistent with experimental and computational results is proposed.