AVS 66th International Symposium & Exhibition
    Fundamental Discoveries in Heterogeneous Catalysis Focus Topic Wednesday Sessions
       Session HC+2D+SS-WeM

Paper HC+2D+SS-WeM12
Oxidation Reactions on Rh(111)

Wednesday, October 23, 2019, 11:40 am, Room A213

Session: Exotic Nanostructured Surfaces for Heterogeneously-Catalyzed Reactions
Presenter: Marie Turano, Loyola University Chicago
Authors: M.E. Turano, Loyola University Chicago
G. Hildebrandt, Loyola University Chicago
R.G. Farber, The University of Chicago
D.R. Killelea, Loyola University Chicago
Correspondent: Click to Email
The uptake and subsequent surface structures of oxygen on transition metal surfaces reveal much about the reactivity of the metal catalyst. On clean Rh(111) at room temperatures in ultra high vacuum (UHV), oxygen molecules (O2) readily dissociate into two adsorbed oxygen atoms, asymptotically approaching a saturation coverage of 0.5 monolayers (ML, 1 ML= 1.5×1015 O atoms cm-2). However, exposing Rh(111) to gas-phase oxygen atoms (atomic oxygen, AO) generated by thermally cracking molecular oxygen over a hot Ir filament, allows for higher oxygen coverages. In addition, oxygen not only adsorbs to the surface, but it may also penetrate into the subsurface region of the crystal. After atomic oxygen exposures at elevated temperatures, the Rh(111) surface is covered in a combination of oxides, adsorbed surface oxygen, and subsurface oxygen (Osub). The coexistence of a variety of structures allows for the determination of which species is reactive to the oxidation of carbon monoxide (CO) on highly oxidized Rh(111) surfaces. Using scanning tunneling microscopy (STM), we have determined that CO oxidation occurs mainly at the interface between the metallic and oxidic surface phases on Rh(111) where the Osub, upon emergence from the bulk, replenishes the surface oxygen. Once Osub is depleted, CO consumes the oxide and the surface quickly degrades into the (2×2)-O+CO adlayer.