To improve fuel efficiency, advanced combustion engines are being designed to minimize the amount of heat wasted in the exhaust. Hence, future generations of catalysts must perform at temperatures that are 100°C lower than current exhaust-treatment catalysts. Achieving low-temperature activity, while surviving the harsh conditions encountered at high engine loads, remains a formidable challenge. In this study, we demonstrate how atomically dispersed ionic platinum (Pt) on ceria (CeO), which is already thermally stable, can be activated via steam treatment (at 750°C) to simultaneously achieve the goals of low-temperature carbon monoxide (CO) oxidation activity while providing outstanding hydrothermal stability. A new type of active site is created on CeO in the vicinity of Pt, which provides the improved reactivity. These active sites are stable up to 800°C in oxidizing environments.

CeO 2 nanooctahedrons, nanorods, and nanocubes were prepared by the hydrothermal method and were then used as supports of Cu-based catalysts for the water-gas shift (WGS) reaction. The chemical and physical properties of these catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption/desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H 2 -TPR) and in situ diffuse reflectance infra-red fourier transform spectroscopy (DRIFTS) techniques. Characterization results indicate that the morphology of the CeO 2 supports, originating from the selective exposure of different crystal planes, has a distinct impact on the dispersion of Cu and the catalytic properties. The nanooctahedron CeO 2 catalyst (Cu-CeO 2 -O) showed the best dispersion of Cu, the largest amount of moderate copper oxide, and the strongest Cu-support interaction. Consequently, the Cu-CeO 2 -O catalyst exhibited the highest CO conversion at the temperature range of 150-250 • C when compared with the nanocube and nanorod Cu-CeO 2 catalysts. The optimized Cu content of the Cu-CeO 2 -O catalysts is 10 wt % and the CO conversion reaches 91.3% at 300 • C. A distinctive profile assigned to the evolution of different types of carbonate species was observed in the 1000-1800 cm −1 region of the in situ DRIFTS spectra and a particular type of carbonate species was identified as a potential key reaction intermediate at low temperature.

In the present work, the stabilities of three low-index ceria (CeO 2 ) 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 CeO 2 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 CeO 2 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 CeO 2 nanoparticle is dominated by the hydroxylated (110) structure. The morphology and stability of a cuboctahedron Pt 13 nanocluster supported on CeO 2 surfaces in both gas and aqueous phases were further investigated. Because of the strong metal−support interaction, AIMD simulations show that the supported Pt 13 nanocluster has the tendency to wet the CeO 2 surface in the gas phase. The calculated interaction energies suggest that the CeO 2 (110) surface provides the best stability for the Pt 13 nanocluster. The CeO 2 -supported Pt 13 nanoclusters are oxidized. The morphology of the CeO 2 -supported Pt 13 nanocluster is less distorted because of the solvation effect in the aqueous phase. Compared with the gas phase, more electrons are transferred from the Pt 13 nanocluster to the CeO 2 support, implying the supported Pt 13 nanocluster is further oxidized in the aqueous phase.