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

In the present paper, different types of metal doped ceria CeO(2)-MO(x) (M=Sc, Y, Dy, Zr and Hf) with fluorite structures have been prepared with a complex polymerization method. The O(2)-releasing potential of prepared samples was evaluated at 1773 K for two-step water splitting process The partially oxygen defected CeO(2)-MO(15) mixed oxides (M = Sc(3+), Y(3+) and Dy(3+)) exhibited an enhancement of the 02 evolution due to the crystal-chemical effect that cation with smaller ionic radius (Sc(3+), Y(3+) and Dy(3+)) mitigate the volume expansion of crystal lattice resulted in the reduction of Ce(4+) with smaller ionic radius into Ce(3+) with larger ionic radius. The CeO(2)-MO(2) (M = Zr(4+) and Hf(4+)) produced larger amount of O(2) than that for CeO(2)-MO(15) mixed oxides, since CeO(2)-MO(2) has no oxygen vacancy. While the ionic radii of Zr(4+) and Hf(4+) are almost equal, the higher O(2)-releasing reactivity of Ce(0) (9)Hf(0) (1)O(2) than that of Ce(0) (9)Zr(0) (1)O(2) is explained in terms of tonicity of M-O bond Thus, it was found that both ionic radius and tonicity play important role in the O(2)-releasing reaction.