Influence on pretreatment in CeO₂ and Au/CeO₂ nanocomposite to improve the creation of surface defects enabling modification in optical interband

In this work, we study the in situ behavior of CeO2 and Au/CeO2 during different pretreatments in temperature and atmosphere by Raman and UV-Vis diffuse reflectance. This procedure allows following in real-time the surface changes of Au nanoparticles and CeO2. A logarithmic correlation between the CeO2 lattice structural defects and the electronic states in the optical interband was obtained. In the case of Au/CeO2, Au nanoparticles over the CeO2 surface allow enhancing the properties formed by the electronic states between the valence band and the conduction band, increasing more than twice the structural defects compared to bare CeO2. Furthermore, we verified that the conservation of oxygen vacancies is due to the pretreatment during a redox cycle. We emphasize the importance of the electronic properties of CeO2 for a better understanding of the effect of pretreatments on Au/CeO2 nanocomposite before its catalytic or photocatalytic applications.

Keywords: Cerium oxide, gold nanoparticles, in situ analysis, DR UV-Vis spectroscopy, Raman spectroscopy, band gap energy, Urbach energy.