Stable and Catalytically Active Shape-Engineered Cerium Oxide Nanorods by Controlled Doping of Aluminum Cations.

Abstract

Shape-engineered nanocrystals (SENs) promise a better selectivity and a higher activity in catalytic reactions than the corresponding non-shape-engineered ones because of their larger specific surface areas and desirable crystal facets. However, often, it is challenging to apply SENs in practical catalytic applications at high reaction temperatures, where SENs deforms into more stable, less active nanoparticles. In this paper, we show that atomic layer deposition (ALD) of Al2O3 at 200 °C can controllably dope Al cations into the shape-engineered CeO2 nanorods (NRs) to not only increase their shape transition temperature from 400 °C to beyond 700 °C but also greatly increase their specific reversible oxygen storage capacity (srOSC). The substituted Al3+ ions impede the surface diffusion of Ce ions and therefore improve the thermal stability of CeO2 NRs. These Al3+ dopants form -Al-O-Ce-O- clusters, which are new Ce species and can be reversibly reduced and oxidized at 500-700 °C. This low-temperature chemical doping method decouples the synthesis process of SENs from the doping process and maintains the shape of the SENs during the activation of dopants. This concept could be adopted to enable the applications of other SENs in challenging high-temperature environments.