Contrary to pure Pt, the formation of the second CO 2 * (IM3) becomes the lowest stationary point when increasing the Ge content, i.e., in Pt 4 Ge 3 and Pt 4 Ge 4 . Because CO 2 desorption is slightly endothermic in both cases, CO 2 will easily detach from the cluster. On Pt 4 Ge 3 the oxidation steps are somewhat reversible, while on Pt 4 Ge 4 the first step is very endothermic. From these observations it can be concluded that in either case the surface will be covered by CO*, O* and CO 2 *, but in Pt 4 Ge 3 once CO 2 (g) is formed, the reaction will evolve more easily towards the final product. Furthermore, these two clusters present a higher BE for O 2 than CO, so O* may become the predominant species together with CO 2 *, limiting CO poisoning. The O* in excess should not be considered detrimental since it can still react with CO(g) via the ER channel. In reality, CO is being consumed simultaneously in each one of these routes; in other words, the different pathways are not independent of each other and the reaction should be thought of as a dynamic phenomenon where the coverage of the intermediates obtained through one route may affect the efficiency of the other. Such a relationship cannot be captured with the results obtained so far. In this respect, microkinetic modeling can be a very useful tool to help elucidating the time evolution of complex reaction networks.