Feasibility and efficiency of electrochemical energy conversion in fuel cells or electrolysers depend on the overpotentials of the cell reactions. Tuned electrocatalytic properties of the electrodes can substantially decrease those overpotentials. Many reactions require specific alloy, oxide, or composite materials as electrodes. According to the Sabatier principle, the chemical reactivity of electrocatalysts should be neither too high nor too low. This is often visualized in "volcano curves".

Electrochemical studies at well-defined single crystal surfaces provide an elegant way to systematically explore how far the electrocatalytic activity can be improved through electrode surface structure and composition. In combination with surface sensitive characterization techniques, such studies also provide deeper insights into the atomic and molecular level reaction steps and how these are influenced by the (local) electrode chemistry and structure.

In this presentation, I will give an overview of a combine surface science / electrochemistry study on the structure electrochemical behaviour of bimetallic thin films vapour deposited onto single crystal surfaces. Structure and composition of these films can be precisely analyzed by spectroscopic methods and atomic scale surface imaging [1-3], whereas preparation parameters like deposition rate and sample temperature offer control of the microscopic structure [1].

Using Pt thin films [2] and PtRu surface alloys [1,3] supported on Ru(0001) as examples, I will demonstrate the value of combined studies considering not only the electrochemistry of a surface but also its adsorption properties at the solid/gas interface. In this context, the predictive capability of ab-initio calculations for the properties at both interfaces will be highlighted [2-6].

By surface fabrication through vapour deposition we can experimentally mimic the model structures used in ab-initio based predictions. This makes it a key approach for an in-depth understanding of electrocatalysis through collaboration between theory and experiment.