Spillover Reoxidation of Ceria Nanoparticles

Interest in resolving the mechanisms behind ceria’s activity has been intense due to the numerous industrial applications including those in heterogeneous catalysis. In this work, we study the reduction and reoxidation of ultrathin CeO2(111) nanoislands on Rh(111) and Pt(111) substrates, so-called inverse model catalysts, with a combination of real and reciprocal space techniques based on X-ray photoemission electron microscopy (XPEEM) and low energy electron microscopy. Soft X-ray microfocused illumination was employed to reduce the ceria islands, which we are able to control by varying the oxygen partial pressure within the measurement chamber. Low energy electron diffraction measurements of the irradiated ceria films demonstrate the formation of an ordered array of oxygen vacancies leading to a (√7 × √7)R19.1° superstructure attributed to the ι-phase (Ce7O12)(111). Resonant photoelectron spectroscopy provides the required high sensitivity to detect small changes in Ce3+ concentration. The high spatial ...