The characteristics of oxygen/hydrogen productivity using 30-mol%-M (M = Fe, Co, Ni, Mn)-doped CeO2-delta (30-mol%-M-CeO2-delta) were studied for the thermochemical two-step water splitting cycle comprising TR (thermal reduction) at 1500 degrees C and WD (water decomposition) at 1150 degrees C. The reproducibility of oxygen evolution was evaluated using 30-mol%-M-CeO2-delta and the effects of different M dopants were compared in the TR temperature range of 1200-1500 degrees C. Two solid phases detected in the 30-mol%-M- CeO2-delta powders were involved in the redox reaction of the thermochemical two-step water splitting cycle. Among the M-CeO2-delta samples evaluated, Mn-doped CeO2-delta provided the most stable and reproducible results and the highest reactivity for oxygen evolution at all temperatures employed for the TR step of the thermochemical two-step water-splitting cycle. (C) 2015 Elsevier Ltd. All rights reserved.