Adsorption of aromatics on the (111) surface of PtM and PtM3 (M = Fe, Ni) alloys

Abstract

The adsorption of benzene and phenol was studied on PtM and PtM₃ (111) surfaces, with M being either Ni or Fe. Under vacuum, the most favorable near surface structures showed an enrichment in Pt over the M species. An analysis of the electronic structure of the metal species in the clean surfaces with different near surface structures was done with the d-band model and showed that the Pt's d-states are significantly shifted away from the Fermi level due to the Pt–M interactions while the M species' d-states were less affected, with Ni's d-band shifting closer to the Fermi level and Fe's d-band shifting away from the Fermi level. The adsorption of aromatics, benzene and phenol, on several near surface structures for the PtM and PtM₃ (111) surfaces showed that higher surface M concentrations resulted in a stronger adsorption due to the larger amount of charge transferred between the adsorbate and surface. However, compared to the adsorption of benzene and phenol on monometallic surfaces, the adsorption of these species on the PtM and PtM₃ (111) surfaces was significantly weakened. Overall, our results show that the observed behavior of these Pt/Fe and Pt/Ni alloys is similar to that seen for the previously studied Pd/Fe surfaces. Furthermore, balancing the weakly adsorbing Pt surface species with the more strongly interacting Fe or Ni species can lead to the tailored adsorption of aromatics with applications in both hydrodeoxygenation and hydrogenation reactions by increasing the desorption rate of wanted aromatic products.