Oxygen Exchange between Catalyst and Active Support during CO Oxidation on Rh/CeO₂(111) and Rh/CeO₂(110): Isotope Labeled ¹⁸O 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 CeO2-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 18O. We prepared ∼20 Å 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) × 10–19 J for Rh/CeO2(111) and 2.28(7) × 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).

Unraveling the Interaction between Fe and CeO2(111) through Growth, Structure, and Thermal Stability Studies

“…Cerium dioxide (CeO 2 ), due to its peculiar redox properties and oxygen storage/release capacity (OSRC), has been widely used in many important fields, , such as three-way automobile emission-control catalysis − and water-gas shift reactions. , However, the use of pure CeO 2 is limited by the low reactivity and degradation of OSRC over time . Therefore, noble metals such as Pt, Pd, and Ru are normally introduced into ceria to add catalytic active sites and improve the OSRC. At the same time, the adjustment of ceria to the morphological and electronic structures of the metal makes the chemical properties of the metal on ceria very different from those of the metal bulk counterpart.…”

Carbon Monoxide and Propylene Catalytic Oxidation Activity of Noble Metals (M = Pt, Pd, Ag, and Au) Loaded on the Surface of Ce0.875Zr0.125O2 (110)

“…Cerium oxide (CeO 2 ) has been widely used in the oxidation reactions of CO and HC due to its unique redox properties [5,6]. The state of Ce can easily shuttle between Ce 3+ and Ce 4+ , which gives CeO 2 excellent oxygen-storage capacity (OSC) and a large number of surface oxygen vacancies [7,8].…”

In situ observation of highly oxidized Ru species in Ru/CeO2 catalyst under propane oxidation

“…22,23 Due to high oxygen storage capacity and facile Ce 4+ /Ce 3+ redox cycle, CeO 2 is considered an "active" support. 24,25 During oxidation processes, it can provide an abundance of active oxygen for redox reactions and thus substantially increase the reaction rate. Especially, the signicant catalytic activity of Ru/CeO 2 can be noticed in the oxidation of light hydrocarbons.…”