In Figure we compare the steady-state coverages and the CO 2 turnover frequency (TOF CO2 ) as a function of temperature and CO and O 2 partial pressures of Pt 4 (pure Pt) with the best alloy candidate, i.e., Pt 4 Ge 3 ; the rest are shown in Figure , along with the discussion. A quick glance reveals that Pt 4 exhibits bistable kinetics. Different regimes of slow (severe CO poisoning; Figure , right) and fast (CO poisoning-free; Figure , left) kinetics can be distinguished based on the surface coverages. Similar to Pt extended catalysts, high O 2 pressures are the best conditions to avoid CO poisoning and increase the CO 2 formation rate. At equal CO and O 2 pressures ( Figure , middle), O* (θ O ~0.5 ML) and CO 2 * (θ CO2 ~0.4 ML) become the main species on the surface in the range of 100-225 K. Interestingly, despite using a feed with a CO:O 2 1:1 composition, the CO coverage only amounts to 0.1 ML. In this temperature regime, a disjunctive behavior can be observed. Pt 4 is more reactive in the CO* + O 2 * route than in the CO* + O* one, but simultaneously, exhibits a small O 2 dissociation barrier. This will make the CO* + O 2 * route less probable and CO* elimination will be directed through the slow CO* + O* reaction, resulting in a very low TOF CO2 . The high endothermicity of CO 2 desorption makes CO 2 * block an important portion of the free active sites. It should be noted that O* is constantly reacting with CO in gas-phase via ER mechanism. The empty sites left will either become covered with O* again or CO* and CO 2 * (the latter being more likely). At intermediate temperatures (225-325 K) CO 2 * becomes the predominant species which may be ascribed to an increment in the CO 2 desorption free energy. The TOF CO2 also increases and remains constant at a fairly moderate level (TOF CO2 ~10 -1 s -1 ). Then, from 350 K upwards, a change of mechanism occurs and CO* + O* becomes the main route. The barriers for O 2 dissociation and CO* + O* reaction become lower than the CO* + O 2 * ones. Yet, the difference in binding free energies (BGs) between CO and O 2 becomes more important, and therefore CO poisoning also becomes more pronounced, slowing down the reaction rate.