Oxygen activation on ultra-disperse CeOx clusters deposited on MgO hexagonal plates

PORTELA, RAQUEL; AGUIRRE, ALEJO; FORNERO, ESTEBAN L.; BOSCO MARTA; BAÑARES, MIGUEL ANGEL; COLLINS, SEBASTIAN E.

Grindelwald

Congreso; Operando VII - the 7th International Congress on Operando Spectroscopy.; 2023

Paul Scherrer Institute

A low-loading lanthanide (1.8, 3.5 and 7.2 wt.%) catalysts composed of highly disperse CeO2 nanoparticles(3 nm) and clusters (1-3 nm) and Ce single atoms supported on magnesium oxide hexagonal nanoplates(CeO2/MgO-h) were synthesized. Structural characterization by high resolution transmission electron microscopyindicates that MgO-h exposes -preferably- (111) planes, allowing the anchoring of small and highlydefective cerium oxide particles, clusters and single atoms. Detailed HAADF and electron energy loss spectroscopy(EELS) analysis revealed that part of the cerium cluster/atoms remains in a Ce3+ state. Catalystsshowed enhanced reducibility and better catalytic performance for CO oxidation reaction as compared to aconventional high surface area CeO2 powder. CeO2/MgO-h catalyst presented a lower apparent activation energythan the bulk CeO2 (57 versus 90 kJ/mol, respectively) for CO oxidation. Operando Raman spectroscopyduring CO oxidation shown the presence of the typical symmetrical vibration F2 of CeO2 at 462 cm-1, veryweak and broad, but more interesting, a broad and intense band at 598 cm-1 indicative of the presence ofoxygen defects (oxygen vacancies. In situ infrared showed that high defective CeOx clusters/atoms activatemolecular oxygen as peroxide (O2-2) 860 cm-1 and superoxide (O2-) 1125 cm-1 species, allowing a more efficientpath for CO oxidation.