Study of the charge displacement at constant potential during CO adsorption on Pt(110) and Pt(111) electrodes in contact with a perchloric acid solution

A new electrochemical approach has been made, employing the current—time transient responses when a CO adlayer is formed at a platinum electrode at various controlled potentials where CO oxidation does not take place. The case of Pt(110) is compared with those of Pt(111) and Pt(111) disordered after ten cycles of oxygen adsorption—desorption. In order to avoid interference with anion-specific adsorption, the study was carried out in a perchloric acid solution. There is good agreement between the charge measured by voltammetry in the absence of CO and the charges measured during the current—time transients. This is indicative that the latter charges are produced by the displacement of the species at the interface as a result of CO adlayer formations. The sign of the current transient has been found to depend on the potential at which CO adsorption is carried out. This dependence may be related to the nature of species which are present in the interfacial region, providing new complementary information that voltammetry cannot yield.