Kinetic modeling of the CO oxidation reaction on supported metal clusters

The CO oxidation on Pd is generally considered to be structure insensitive and is not expected to depend on the size of the Pd particles. However, sev eral size effects have already been evidenced for this reaction. Near the t emperature where the steady-state reaction rate is maximum, the reactivity per Pd surface atom (turnover number (TON)) increases for small particles. At low temperature, in transient molecular beam experiments, a second peak of CO2 appears after the CO beam is closed, while the oxygen is still suppl ied to the sample. This peak shifts, and its shape changes with temperature and oxygen pressure. This peak is explained by the presence of CO strongly bound to the particle edges. This strongly bound CO reacts well after the CO adsorbed on the facets has desorbed. A kinetic model is presented which explains the evolution of this peak with temperature and oxygen pressure.