Cerium dioxide as a photocatalyst for water decomposition to O2 in the presence of Ce4+aq and Fe3+aq species

It has been demonstrated that cerium dioxide is a potential photocatalyst that can be used to decompose water to produce oxygen in aqueous suspension containing an electron acceptor, and the optimum parameters for the reaction have been investigated. The O(2) yield strongly depended on the duration of irradiation, CeO(2) concentration, concentration of the electron acceptor, and pH of the suspension. The optimum photoproduction for O(2) was obtained under the following operating conditions: Illumination time: > 10 h, CeO(2) concentration: 2-5 g dm(-3). [Ce(4+)]: 4-5 mM, pH < 3, and illumination wavelength < 420 nm. During long-term runs, CeO(2) suspensions showed a satisfactory photostability and activity even after 400 h of illumination. The obtained data show that, with an appropriate design, cerium dioxide is a promising material that can be used as a photoactive component in photocatalytic reactions. The studied system utilizes CeO(2) to accomplish the initial light absorption, charge separation, and O(2) evolution from the interaction of water molecules with holes photogenerated in the CeO(2) valence band, in the presence of Ce(aq)(4+) or Fe(aq)(3+) species as an acceptor of conduction band electrons. (C) 2000 Elsevier Science B.V. All rights reserved.