In Situ Observation of Competitive CO and O₂ Adsorption on the Pt(111) Surface Using Near-Ambient Pressure Scanning Tunneling Microscopy

Abstract

We investigated the competitive coadsorption of CO and O2 molecules on a Pt model surface using a catalytic reactor integrated with a scanning tunneling microscope at elevated pressure. CO-poisoned incommensurate atom-resolved structures are observed on the terrace sites of the Pt(111) surface under gaseous mixtures of CO and O2. However, in situ surface measurements revealed that segmented local structures were influenced by the CO/O2 partial pressures in the catalytic reactor at a total pressure of a few Torr. This could be related to the expected formation of the theoretical oxygen precursor intermediates during dissociation of O2 on the surface before the chemical reaction. These findings provide microscopic insights into the early steps of the catalytic reaction pathways on the Pt surface during CO oxidation in an industrial chemical reactor.