Dynamics of catalytic ammonia oxidation over Rh(111) surfaces

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In this project we plan to study chemical wave patterns and kinetic instabilities in catalytic ammonia oxidation over a flat and a stepped Rh(111) surface, Rh(533). Photoemission electron microscopy (PEEM) and low energy electron microscopy (LEEM) shall be employed as spatially resolving in situ methods. The main motivation is to come to a mechanistic understanding of a new type of front instability we observed recently in a similar but structurally more complex system, Rh(110)/NH3 + O2. In the bistable regime this instability caused a sideways displacement of the interface which propagated in wave-like manner along the front line. A realistic model of the reaction system shall be developed. In parallel we will try to analyze the instabilities with a general model of an excitable reaction-diffusion system based on equations of the FitzHugh-Nagumo and of the Allen-Kahn type.