Sulfur Dioxide and Hydrogen Adsorption on Pt3Co(111) Surfaces: A First Principles Study

Abstract

Interactions between sulfur dioxide, SO2, and hydrogen on two different surfaces of Pt3Co(111) were investigated using density functional theory. The two surfaces considered were a Pt-skin and Ll2 Pt3Co(111) surface. SO2 adsorption was found to be more favorable on the Ll2 surface owing to its d-band center being closer to the Fermi energy. However, both surfaces adsorbed SO2 more weakly in comparison to Pt(111). The adsorption energies of H follow the same adsorption energy trends as SO2 on the different surfaces and show a preference for the three fold-hollow sites similar to other fcc metal (111) surfaces. The weaker adsorption of SO2 on the alloy Pt3Co(111) surfaces agree well with experimental observations that removal of sulfur to attain the initial mass of activity of the catalysts prior to sulfur adsorption requires less cleaning cycles for the alloy. Additionally, our results indicate that less hydrogen adsorbs to alloy surfaces than to pure Pt(111), also in agreement with experiment. SO2 adsorption trends across the three surfaces closely mirror those of atomic sulfur, indicating that surface sulfur tolerance does not depend on the specific oxidation species.