The inverse catalyst 'cerium oxide (ceria) on copper' has attracted much interest in recent time because of its promising catalytic activity in the water-gas-shift reaction and the hydrogenation of CO 2. For such reactions it is important to study the redox behaviour of this system, in particular with respect to the reduction by H 2. Here, we investigate the high-temperature O 2 oxidation and H 2 reduction of ceria nanoparticles (NP) and a Cu(111) support by low energy electron diffraction (LEED), scanning tunnelling microscopy (STM), noncontact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM). After oxidation at 550°C, the ceria NPs and the Cu(111) support are fully oxidized, with the copper oxide exhibiting a new oxide structure as verified by LEED and STM. We show that a high H2 dosage in the kilo Langmuir range is needed to entirely reduce the copper support at 550°C. A work function (WF) difference of Dφ rCeria/Cu-Cu ≈-0.6 eV between the ceria NPs and the metallic Cu(111) support is measured, with the Cu(111) surface showing no signatures of separated and confined surface regions composed by a CuCe alloy. After oxidation, the WF difference is close to zero (Dφ Ceria/Cu-Cu ≈-0.1. .. 0 eV), which probably is due to a WF change of both, ceria and copper.