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Coordinator: Sergio Valeri

Members: The research group of catalysis is composed by Umberto del Pennino, Sergio D’Addato, Rita Magri Magri e Paola Luches (ricercatore esterno)..

The goal of the activity is the design of efficient nanostructured materials in which the amount of critical (expensive, rare,…) metals is minimized, and the working temperature is decreased.

The activity is mainly focused on the optimization of reducibility in cerium and titanium oxide based films and nanoparticles. We investigate the modification of the electronic properties and of oxygen vacancy formation energy induced by reduced dimensionality and proximity with metals in the form of supported nanoparticles or as dopants.

Available growth facilities include molecular beam epitaxy, magnetron sputtering and mass-selected nanoparticle growth by magnetron sputtering and inert gas aggregation. The systems are characterized by in-situ by XPS, STM/AFM, LEED and ex-situ by SEM, HR-TEM/STEM, XAFS, etc.

Examples of recent activity include:

1) Study of reduction and oxidation processes in cerium oxide ultrathin films during thermal cycles in vacuum and oxygen partial pressure.
The reducibility of cerium oxide epitaxial nanostructures is observed to be enhanced compared to continuous films of a few nm thickness. Metastable reduced structural phases are observed in proximity with the Pt(111) surface.

2) Structure and charge transfer in Ag nanoparticles supported on cerium oxide.
An important contraction in the structure of Ag nanoparticles, together with a significant charge transfer between CeO2 and supported Ag nanoparticle, are observed, and expected to give origin to different properties in the combined system, compared to its individual components.

3) Atomic scale structure and reduction at the interface between cerium oxide and platinum.
Local modifications of the registry between the cerium oxide and platinum lattices and the occurrence of nanometric platinum islands are observed by aberration corrected STEM at the interface between the two materials. A non negligible reduction of the cerium oxide interfacial layers is observed and it is rationalized in terms of interfacial charge transfer