On the electrochemical properties of platinum stepped surfaces vicinal to the (100) pole. A computational study

Abstract

DFT studies on platinum stepped surfaces have been carried out in order to understand the differences in the electrochemical behavior between the surfaces with (111) and (100) terraces. Thus, adsorption energies of different species on selected surfaces have been computed. For the adsorption of Bi and Cu on the Pt(553) and Pt(711) surfaces, it has been found that that the adsorption energy on the site corresponding to the step decoration for the Pt(553) surface is ca. 0.5 eV higher than that calculated on the (111) terrace sites. On the other hand, there is no preferential adsorption site for Cu or Bi on the Pt(711) surface, since the energy differences between the different sites on this stepped surface with (100) terraces are very small. CO and OH adsorption on the surface with (100) terraces, namely the Pt(100), the Pt(711) and the Pt(510) surfaces, have been also investigated. The energy differences between step sites and terrace sites for both surfaces is very small, ca. 0.2 eV for OH adsorption and <0.1 eV for CO adsorption. For OH, the preferred adsorption mode is a bridge mode, whereas the adsorption energy for the on top and bridge configurations of CO are similar on those surfaces. The comparison with previous DFT calculations indicates that the perturbation created by the step on the (100) terrace is significantly smaller than that created on the (111) terraces. Thus, the modification of the electrochemical properties produced by the presence of a step in the (100) terrace is minor, in agreement with the experimental results.