On the complex structure of reaction-diffusion fronts observed during CO oxidation on Pt{100}

In the catalytic oxidation of CO on Pt{100}, we have been able to identify, using small-area LEED, the different adsorbate-covered regions which constitute the reaction-diffusion fronts observed in photoelectron emission microscopy. The resulting concentration profile is simulated in one dimension with the help of a simple two-variable model derived from the Langmuir-Hinshelwood mechanism. The characteristic features of the experiment arc reproduced if it is assumed that the CO diffusion coefficient is strongly enhanced (by a factor of 7) at coverages corresponding to the (√2 × √2)R45°-CO phase and reduced by surface defects