The effect of the electrode potential in the reactivity of platinum stepped single crystal electrodes with (111) terraces towards CO oxidation has been studied. It is found that the CO adlayer is significantly affected by the potential at which the adlayer is formed. The electrochemical and FTIR experiments show that adsorbed CO layer formed in acidic solution at ~0.03 V vs. SHE is different from that formed at -0.67 V vs. SHE in alkaline solutions. The major effect of the electrode potential is a change in the long-range structure of CO adlayer. The adlayer formed in alkaline media presents a higher number of defects. These differences affect the onset and peak potential for CO stripping experiments. The stripping voltammogram for the adlayer formed at -0.67 V vs. SHE always shows a pre-wave and the peak potential is more negative than that observed for the adlayer formed at 0.03 V vs. SHE. This means that the apparent higher activity for CO oxidation observed in alkaline media is a consequence of the different CO adlayer structure on the (111) terrace, and not a true catalytic effect. The different behavior is discussed in terms of the different mobility of CO observed depending on the electrode potential. Also, the FTIR frequencies are used to estimate the pzc (potential of zero charge) for the Pt(111) electrode covered with a CO adlayer.
Please cite this article as: Adolfo Ferre-VilaplanaRuben GisbertEnrique Herrero On the electrochemical properties of platinum stepped surfaces vicinal to the (100) pole. A computational study (2014), http://dx.doi.org/10.1016/j.electacta. 2014.01.138 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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 Page 2 of 29 A c c e p t e d M a n u s c r i p t 2 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.
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