Effects of CeO2 additive on redox characteristics of Fe-based mixed oxide mediums for storage and production of hydrogen

Effects of CeO2 additive to Fe-based mixed oxide mediums with Rh and ZrO2 for chemical hydrogen storage were investigated in terms of stability and reactivity of the mediums in water splitting oxidation with repeated redox cycles. The mediums with CeO2 content ranging from 0 to 30 wt% were prepared by co-precipitation method using urea solution as a precipitant. The hydrogen storage and release properties were investigated during repeated isothermal redox cycles at 823 K for reduction with hydrogen and 623 K for oxidation with water vapor under atmospheric pressure. The amount of hydrogen produced by the mediums, both with and without CeO2, was maintained at an almost constant level over ten repeated redox cycles. However, the oxidation rates of the mediums without CeO2 were decreased during repeated redox cycles while that increased with increasing CeO2 contents. Especially, the mediums added with 30 wt% of CeO2 (FRZC-30) showed high activity and stability for ten redox cycles, the degree of hydrogen storage was almost maintained ca. 1.9 wt% on the basis of total amount of the medium.