Density Functional Theory Study on Propane and Propene Adsorption on Pt(111) and PtSn Alloy Surfaces

Density functional theory calculations were performed to investigate the adsorption of propane, propene, and C and H atoms on Pt and PtSn surfaces employing the revised Perdew - Burke - Ernzerhof (RP BE) and vdW-DF functionals. Propane adsorption was found to be mediated by van der Waals interactions without significant site preference on any of the studied surfaces. The adsorption characteristics of propene are different: On the Pt(111) and Pt3Sn(111) surfaces, propene adsorption is covalent, and the molecule prefers a di-sigma site to a pi site. Alloying Pt(111) with Sn leads to weaker adsorption owing to geometric and relaxation effects, whereas electronic effects are found to be small. On the PtSn2(111) surface, propene adsorption is weak and dominated by van der Waals interactions. Our calculations show that addition of Sn leads to unfavorable geometric and electronic effects on the adsorption of carbon and hydrogen atoms. The impact of alloying with Sn on the selective propane dehydrogenation to propene is discussed.