Oxygen Exchange between Catalyst and Active Support during CO Oxidation on Rh/CeO2(111) and Rh/CeO2(110): Isotope Labeled O-18 Study
Abstract
Rhodium (Rh) is used predominantly in the automotive industry for three-way catalysis (TWC). CO oxidation efficiency during TWC can be significantly improved by adding CeO 2 -active support known for its oxygen storage capacity (OSC).
In this work, the CO oxidation mechanism of Rh nanoparticles on CeO2(111) and CeO2(110) was studied with the focus on oxygen exchange between catalytic particles and active support. This exchange is analyzed utilizing isotopically labeled O-18.
We prepared similar to 20 angstrom oriented CeO2 layer by evaporation on Rh(111) and Rh(110) single crystals followed by Rh deposition of 10-20 nm particles. These model catalysts are studied by means of TDS, MB adsorption, TPR, AFM, LEED, and XPS.
The reaction achieves higher performance on Rh/CeO2(110). It is explained by the slightly weaker CO-Rh bond and the higher oxygen exchange activity.
CO desorption energies at zero coverage are 2.39(7) X 10(-19) J for Rh/CeO2(111) and 2.28(7) X 10(-)(19) J for Rh/CeO2(110). We observed the diffusion of oxygen from molecular beams into the CeO2 support and measured a contribution of CeO2 oxygen to the reaction.
During low-pressure reaction cycles with temperature range 300-770 K, the produced CO2 contains 53% of oxygen from the support for Rh/CeO2(111) and 70% for Rh/CeO2(110).