This paper reports on electrochemical hydrogen oxidation at atomically smooth single crystal surfaces. These surfaces are considered as planar models for (bi)metallic nanoparticles that are commonly used as catalytically active electrode materials in low-temperature fuel cells. These samples are prepared in ultrahigh vacuum but are characterized under conditions of enhanced mass transport in hydrogen saturated electrolyte. The two examples shown in this paper are Ru(0001) with or without an atomically thin layer of Pt. The Pt thin layer turns out to be more active than pure Ru(0001) by three orders of magnitude and also more active than bulk Pt electrodes. We show that those findings agree very well with predictions based on density functional theory in combination with a simple kinetic model.
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