Understanding the roles of electronic effect in CO on Pt-Sn alloy surface via band structure measurements

TL;DR

This study uses angle-resolved photoemission spectroscopy to investigate how electronic effects influence CO chemisorption on Pt and Pt-Sn alloy surfaces, revealing charge transfer mechanisms and orbital interactions.

Contribution

It provides direct experimental evidence of charge transfer and orbital participation in CO adsorption on Pt-Sn alloys, highlighting electronic effects distinct from pure Pt surfaces.

Findings

Charge transfer between CO and metal surfaces observed.

Distinct orbital signatures identified in band structure.

Pt surface shows larger charge change than Pt-Sn upon CO adsorption.

Abstract

Using angle-resolved photoemission spectroscopy, we show the direct evidence of charge transfer between adsorbed molecules and metal substrate, i.e. chemisorption of CO on Pt(111) and Pt-Sn/Pt(111) 2x2 surfaces. The observed band structure shows a unique signature of charge transfer as CO atoms are adsorbed,revealing the roles of specific orbital characters participating in the chemisorption process. As the coverage of CO increases, the degree of charge transfer between CO and Pt shows clear difference to that of Pt-Sn. With comparison to DFT calculation results, the observed distinct features in the band structure are interpreted as backdonation bonding states of Pt molecular orbital to the 2{\pi} orbital of CO. Furthermore, the change in the surface charge concentration, measured from the Fermi surface area, shows Pt surface has a larger charge concentration change than Pt-Sn surface upon CO adsorption. The difference in the charge concentration change between Pt and Pt-Sn surfaces reflects the degree of electronic effects during CO adsorption on Pt-Sn.