Adsorption of benzene on defective Pt surfaces: A DFT study

• Adsorption of benzene over defects like vacancies or step edges in Pt(111) is stronger than on perfect surfaces. • The strongest adsorption is found to be over the atop vacancy in case of vacancy defects. • The terrace region close to a step edge favors adsorption on the threefold hollow fcc site. • The step edge favors adsorption on the threefold hollow hcp site. Defects occur naturally on surfaces during formation. The interaction of a benzene molecule with a defective surface of platinum is investigated using plane wave DFT. Adsorption energy, adsorbate geometry and electronic structure of benzene on defective surfaces of platinum is obtained and compared with those on a perfect platinum (111) facet. We observe that the presence of defects in the form of steps and vacancy leads to an increase in the strength of adsorption. It is found that the atop is the most stable site for adsorption on a Pt (111) surface having a vacancy defect, which agrees with the available experimental results. The terrace region, which has a symmetry similar to a perfect Pt(111) surface, gives the 3-fold symmetric fcc hollow site as energetically preferred for adsorption. The step edge has the hcp hollow as the preferred site for adsorption. Analysis of electronic structure and charge transfer at the preferred sites is performed. The presence of defects brings out major changes in adsorption process, as compared to that on perfect surfaces. Reduction in coordination of surface sites due to defects is identified as the main reason for more reactive nature of defective surfaces.