Active and Stable Embedded Au@CeO2 Catalysts for Preferential Oxidation of CO

We present a way to stabilize the Au phase supported on ceria by encapsulation of preformed Au nanoparticles (Au NPs) inside a porous ceria layer. The functionalization of the surface of the nanoparticles with carboxylic groups provides the link between the metal phase and the growing Ce(OH)x barrier, which is then transformed during calcination to obtain the final Au@CeO2 materials. The sample with a metal loading of 1 wt % shows good activity under real PReferential OXidation (PROX) conditions and better activity than catalysts of higher metal loadings or prepared through optimized deposition-precipitation methods described in the literature. Under simulated aging, the Au(1 wt %)@CeO2 sample exhibits minor deactivation, which is mainly associated with the formation of carbonates that can be reversed by a mild regenerative oxidative treatment to fully restore its initial activity. Vice versa, the other catalysts show either the unavoidable reversible carbonate poisoning or the irreversible deactivation due to metal sintering/agglomeration phenomena. A plethora of characterization techniques (CO chemisorption, X-ray diffraction, X-ray absorption spectroscopy, aberration-corrected scanning transmission electron microscopy) has been used to confirm the structure of these catalysts and to identify the underlying phenomena controlling their activity.