Oxygen and hydrogen productivities and repeatable reactivity of 30-mol%-Fe-, Co-, Ni-, Mn-doped CeO2−δ for thermochemical two-step water-splitting cycle

The characteristics of oxygen/hydrogen productivity using 30-mol%-M (M = Fe, Co, Ni, Mn)-doped CeO2−δ (30-mol%-M-CeO2−δ) were studied for the thermochemical two-step water splitting cycle comprising TR (thermal reduction) at 1500 °C and WD (water decomposition) at 1150 °C. The reproducibility of oxygen evolution was evaluated using 30-mol%-M-CeO2−δ and the effects of different M dopants were compared in the TR temperature range of 1200-1500 °C. Two solid phases detected in the 30-mol%-M- CeO2−δ powders were involved in the redox reaction of the thermochemical two-step water splitting cycle. Among the M-CeO2−δ samples evaluated, Mn-doped CeO2−δ 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.