Strain Field in Ultrasmall Gold Nanoparticles Supported on Cerium-Based Mixed Oxides. Key Influence of the Support Redox State.

Using a method that combines experimental and simulated Aberration-Corrected High Resolution Electron Microscopy images with digital image processing and structure modeling, strain distribution maps within gold nanoparticles relevant to real powder type catalysts, i.e., smaller than 3 nm, and supported on a ceria-based mixed oxide have been determined. The influence of the reduction state of the support and particle size has been examined. In this respect, it has been proven that reduction even at low temperatures induces a much larger compressive strain on the first {111} planes at the interface. This increase in compression fully explains, in accordance with previous DFT calculations, the loss of CO adsorption capacity of the interface area previously reported for Au supported on ceria-based oxides.

Dramatic effect of redox pre-treatments on the CO oxidation activity of Au/Ce(0.50)Tb(0.12)Zr(0.38)O(2-x) catalysts prepared by deposition-precipitation with urea: a nano-analytical and nano-structural study.

Nano-structural and nano-analytical studies show that the dramatic difference in CO oxidation activity observed between two Au/Ce0.50Tb0.12Zr0.38O2-x samples prepared by deposition-precipitation with urea and further activated under oxidising or reducing conditions is due to the poisoning effect of a very thin layer of carbon grown on the pre-reduced catalyst.

Single-step process to prepare CeO2 nanotubes with improved catalytic activity.

CeO(2) nanotubes have been grown electrochemically using a porous alumina membrane as a template. The resulting material has been characterized by means of scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy, high-angle annular dark-field scanning transmission electron microscopy tomography, high-resolution electron microscopy (HREM), and electron energy loss spectroscopy. According to SEM, the outer diameter of the nanotubes corresponds to the pore size (200 nm) of the alumina membrane, and their length ranges between 30 and 40 microm. HREM images have revealed that the width of the nanotube walls is about 6 nm. The catalytic activity of these novel materials for the CO oxidation reaction is compared to that of a polycrystalline powder CeO(2) sample prepared by a conventional route. The activity of the CeO(2) nanotubes is shown to be in the order of 400 times higher per gram of oxide at 200 degrees C (77.2 x 10(-2) cm(3) CO(2) (STP)/(gxs) for the nanotube-shaped CeO(2) and 0.16 x 10(-2) cm(3) CO(2) (STP)/(gxs) for the powder CeO(2)).