Ce(0.9)M(0.1)O(2-delta) ceramics (M = Mg, Ca, Sr, Sc, Y, Dy, Zr and Hf) were synthesized by a polymerized complex method. X-ray powder diffraction (XRD) patterns indicate that solid solutions with a fluorite structure were formed after the synthesis, and this structure was retained after redox cycles. An analysis of the redox cycles using a direct gas mass spectrometer (DGMS) suggests that the reactivity of CeO(2)-based ceramics in the O(2)-releasing step could be enhanced by doping the ceramics with cations with a higher valence and a smaller effective ionic radius. The investigation of two-step water-splitting cycles indicates that the amount of H(2) evolved in the H(2)-generation step is dominated by the amount of O(2) (Ce(3+)) evolved in the O(2)-releasing step. Electrochemical impedance spectroscopy (EIS) investigations show that the higher bulk conductivity of CeO(2)-based ceramics at intermediate temperatures could promote reactivity by enhancing the molar ratio of H(2)-O(2) that is evolved during the two-step water-splitting cycles. The highest reactivity, both in the redox and in the two-step water-splitting cycles, is exhibited by Ce(0.9)Hf(0.1)O(2). Crown Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.