Transforming CeO2 nanoparticles into ultra small ceria clusters on alumina enhances catalytic activity

Ceria nanoparticles supported on alumina have found wide applications for various catalytic reactions, especially in contact with precious metals. We discovered that treatment of these catalysts at temperatures between 750 and ~1,000 ºC under the flow of CO and NO in the presence of steam (reactive aging in reducing atmosphere) leads to dispersion of ceria nanoparticles and creates a novel catalytic architecture with high density (up to 10 wt%) of atomically dispersed, ultra small CexOy clusters densely covering alumina, as confirmed by XPS, FTIR and AC-STEM characterization. These clusters possess markedly higher oxygen mobility (and therefore oxygen storage capacity), leading to easier extraction of oxygen with the formation of abundant Ce+3 sites and oxygen vacancies. Because of this, these catalysts (in the absence or presence noble metals, such as Rh and Pt) possess much improved activity for multiple industrially important catalytic reactions such as NO and N2O reduction, as well as CO and NO oxidation even after exposure to harsh aging conditions, with activity superior to fresh catalyst even for aged samples, providing a general pathway to creating more efficient PGM/ceria catalysts. Our study therefore reveals novel catalyst architecture with atomically dispersed ceria clusters with superior redox properties under conditions where typical catalyst sintering is generally assumed to occur and allows to utilize these materials as supports for more effective general catalysis.