During CO‐oxidation on Pt(100), CO diffuses in a ‘‘disordered environment’’ produced by a complex pattern of reconstructed and unreconstructed regions of the substrate. Macroscopic diffusion of CO is effectively only possible on percolating 1×1‐regions of the substrate. We treat the spatio‐temporal behavior observed in this reaction system accounting in the simple way for the percolative nature of CO‐diffusion. This is done via incorporation into the reaction‐diffusion equations of a suitable chemical diffusion coefficient, exploiting ideas from the theory of transport in disordered media. We use these equations to analyze the propagation of reactive, O‐rich pulses into a CO‐covered 1×1‐background.
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