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.