Fourier-transform Infrared (FTIR) spectroscopy is a powerful technique for identification of small molecules adsorbed to metal surfaces. We have added FTIR to an ultra-high vacuum (UHV) chamber as a non-destructive and highly sensitive surface analysis technique. Because IR measurements can be performed in UHV conditions, interference from atmospheric species are avoided, while enabling investigation of catalytic systems, like carbon monoxide (CO) to carbon dioxide (CO2) on Rh(111). To determine the reactivity of the various oxide phases, the oxidation reaction of CO to CO2 on oxidized Rhodium (Rh) will be utilized as a probe reaction. We will be able to determine the chemical significance of various oxygen phases on different Rh surfaces, and the CO coverage and binding sites on the different oxygenaceous phases. Studying CO oxidation on different Rh surfaces will provide atomic level information regarding oxidation reactions, progressing the understanding of various surface phases relevant to many Rh catalyzed processes. Past exposure conditions determined that at low temperatures, CO was observed to adsorb along (2x1)-O and RhO2 domain boundaries, and Osub replenished the reacted oxygen at these boundaries at higher temperatures. When CO was prolonged exposure it consumed all Osub and reacted with oxides at the defects. In recent studies, it was determined that there are multiple reaction pathways available for CO oxidation, but at temperatures at or below 350K reaction sites are not regenerate. Via FTIR, these and other reaction sites of CO oxidation will be investigated to determine reaction pathways or mechanisms.

Investigation of CO oxidation on Rh(111) with IRRAS

ACS Spring 2022

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