Development of the Visible-Light Response of CeO2-x with a high Ce3+ Content and Its Photocatalytic Properties

Photocatalysts that are responsive to visible light are necessary to utilize solar energy. We prepared reduced CeO2-x with absorption in the visible region by a simple solvothermal method. A new absorption band appearing at lambda approximate to 500nm (surface plasmon resonance) could be ascribed to the high content of Ce3+. To elucidate the relationship between Ce3+ and activity, the decomposition of isopropyl alcohol (IPA) to generate acetone was performed under visible-light irradiation. CeO2-x showed activity that was superior to that of pure CeO2. Ce3+ induced oxygen vacancies in the lattice of CeO2-x, and this resulted in an improvement in the activity. In addition, the introduction of Ce3+ resulted in an improvement in the absorption of CeO2-x in the visible-light region. Also, the appearance of small tentacles (Confeito-like) on the surface of CeO2-x not only provided more active sites but also prevented aggregation. Owing to its visible-light responsiveness and unique morphology, the performance of this material was significantly improved relative to that of pure CeO2.