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 CeO 2− x with absorption in the visible region by a simple solvothermal method. A new absorption band appearing at λ≈500 nm (surface plasmon resonance) could be ascribed to the high content of Ce 3+ . To elucidate the relationship between Ce 3+ and activity, the decomposition of isopropyl alcohol (IPA) to generate acetone was performed under visible‐light irradiation. CeO 2− x showed activity that was superior to that of pure CeO 2 . Ce 3+ induced oxygen vacancies in the lattice of CeO 2− x , and this resulted in an improvement in the activity. In addition, the introduction of Ce 3+ resulted in an improvement in the absorption of CeO 2− x in the visible‐light region. Also, the appearance of small tentacles (Confeito‐like) on the surface of CeO 2− 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 CeO 2 .