Inhibition of hydrogen adsorption and evolution by CO on Pt(111) and Pt(100) electrodes

The inhibition of the hydrogen adsorption and evolution reactions by adsorbed CO on Pt(111) and Pt(100) electrodes has been studied. One significant feature of both inhibitory processes is their dependence on the structure. In the case of the hydrogen adsorption reaction it has been found that the effect caused by CO can be explained in terms of a third body effect. The differences found between the Pt(111) and Pt(100) electrodes are brought about by the different adsorption geometries of the CO molecule on both substrates. In the case of the hydrogen evolution reaction, the inhibitory effect is mole important for both orientations and also structure-sensitive. In order to explain the influence of CO on the HER we use the Infected Zone Model, which considers the existence of partially active, infected sites in addition to the active and blocked sites.