O2 Releasing Reactivity of Ceria-Based Reactive Ceramics on Irradiation of Concentrated Solar Beam for Solar Hydrogen Production

Abstract

In the present paper, different types of metal doped ceria CeO2-MOx (M = Sc, Y, Dy, Zr and Hf) with fluorite structures have been prepared with a complex polymerization method. The O2-releasing potential of prepared samples was evaluated at 1773 K for two-step water splitting process. The partially oxygen defected CeO2-MO1.5 mixed oxides (M = Sc3+, Y3+ and Dy3+) exhibited an enhancement of the O2 evolution due to the crystal-chemical effect that cation with smaller ionic radius (Sc3+, Y3+ and Dy3+) mitigate the volume expansion of crystal lattice resulted in the reduction of Ce4+ with smaller ionic radius into Ce3+ with larger ionic radius. The CeO2-MO2 (M = Zr4+ and Hf4+) produced larger amount of O2 than that for CeO2-MO1.5 mixed oxides, since CeO2-MO2 has no oxygen vacancy. While the ionic radii of Zr4+ and Hf4+ are almost equal, the higher O2-releasing reactivity of Ce0.9Hf0.1O2 than that of Ce0.9Zr0.1O2 is explained in terms of ionicity of M-O bond. Thus, it was found that both ionic radius and ionicity play important role in the O2-releasing reaction.