It is extremely important to consider the statistical weights of each reaction channel. Indeed, the most likely reaction mechanism for LH will be connected to atomic oxygen. In this case bimetallic clusters present lower energy barriers as compared to pure Pt, as well as the inhibition of the CO and CO 2 poisoning effects. For the sake of comparison, the complete potential energy diagram of the LH mechanism with predissociated oxygen on all the Pt 4 Ge n nanoclusters is illustrated in Figure (the reader is referred to Figure for the results of the other cases). It can be observed that the LH mechanism lies lower in energy than ER since it includes the adsorption of both O 2 and CO, while ER is missing the adsorption of CO. In the ER mechanism for both CO(g) + O 2 * and CO(g) + 2 ✕ O* (Figure ), all steps are exothermic (downhill) for all clusters, the CO 2 release being the most stable state. Consequently, this state will act as a thermodynamic sink shifting the reaction towards CO 2 formation, regardless of the Ge concentration. Notwithstanding, as shown in Figure , in the LH mechanisms O* + CO* (IS3, O* + CO*) becomes the most stable state for Pt 4 , Pt 4 Ge and Pt 4 Ge 2 due to the endothermic nature of the last two steps (second oxidation + desorption). This indicates that IS3 will act as a drain and shift the reaction towards CO* + O* formation. In this state O* could still react with CO in gas-phase via ER mechanism, but part of the surface will be poisoned by CO. The case of Pt 4 is more dramatic since CO 2 desorption is highly endothermic, which means that part of the formed CO 2 will remain on the surface, i.e., Pt 4 will be poisoned by CO 2 as well as CO.