Reactivity and thermal stability of oxidized copper clusters on the tantalum(V) oxide surface

Oxidized copper clusters 2–5 nm in size have been obtained by RF discharge sputtering of a copper wire in an oxygen atmosphere. Isolated CuO clusters or, at long deposition times, their agglomerates form on the support. The thermal stability of the oxidized nanoparticles in a vacuum and their reactivity toward CO in relation to the deposition time have been investigated by X-ray photoelectron spectroscopy. The asprepared clusters show low reactivity (10^?7?10^?9), but their activation by reduction and subsequent reoxidation in an oxygen medium raises their reactivity to ～10^?5. This is due to the appearance of weakly charged oxygen species on the surface. The reactivity of the CuO clusters has been compared to the reactivity of earlier studied nanosized copper oxide model objects.