Tailoring the Adsorption of Benzene on PdFe Surfaces: A Density Functional Theory Study

Bimetallic surfaces have been found to greatly improve the performance of numerous chemical processes due to synergistic interactions between the metal components. To be able to tailor the adsorption of aromatic molecules of these surfaces, the synergistic interactions within the surface and their effects on adsorbates must be elucidated. In this work, we examine the energetic and electronic interaction between benzene and several model PdFe bimetallic surfaces, with low and high Pd coverage limits, using density functional theory and compare our results with the adsorption of benzene on a pure Fe (110) surface. The adsorption energy trends on these model surfaces show that the interactions between the Pd and Fe significantly decrease the strength of benzene's adsorption on surface Pd without significantly weakening its adsorption on the adjacent surface Fe. From the electronic analyses, the decreased adsorption strength of benzene on the model PdFe surfaces is due to the shift in the Pd's d-band center away from the Fermi level. These results show that aromatic compounds will preferentially adsorb onto any exposed Fe in a PdFe surface due to the greater availability of electronic states near the Fermi level. Therefore, under typical catalytic conditions, the strength of the adsorption of benzene can be tailored on the basis of the amount of Pd added to an Fe surface because increasing the concentration of Pd in the surface will increase the amount of interaction between the adsorbate and the modified surface Pd.