Theoretical Investigation of the Structural Stabilities of Ceria Surfaces and Supported Metal Nanocluster in Vapor and Aqueous Phases

Abstract

In the present work, the stabilities of three low-index ceria (CeO2) surfaces, that is, (111), (110), and (100) in vapor and aqueous phases were studied using ab initio molecular dynamics (AIMD) simulations and density functional theory calculations. On the basis of the calculated Gibbs surface free energies, the morphology and exposed surface structures of the CeO2 nanoparticle were predicted using the Wulff construction principle. It is found that the partially hydroxylated (111) and (100) are two major surface structures of the CeO2 nanoparticle in the vapor phase at ambient temperature. As the temperature increases, the fully dehydrated (111) surface becomes the most dominant structure. However, in the aqueous phase, the exposed surface of the CeO2 nanoparticle is dominated by the hydroxylated (110) structure. The morphology and stability of a cuboctahedron Pt13 nanocluster supported on CeO2 surfaces in both gas and aqueous phases were further investigated. Because of the strong metal–support interaction, AIMD simulations show that the supported Pt13 nanocluster has the tendency to wet the CeO2 surface in the gas phase. The calculated interaction energies suggest that the CeO2(110) surface provides the best stability for the Pt13 nanocluster. The CeO2-supported Pt13 nanoclusters are oxidized. The morphology of the CeO2-supported Pt13 nanocluster is less distorted because of the solvation effect in the aqueous phase. Compared with the gas phase, more electrons are transferred from the Pt13 nanocluster to the CeO2 support, implying the supported Pt13 nanocluster is further oxidized in the aqueous phase.