The use of ferrites as highly active oxygen storage materials for chemical looping hydrogen production under intermediate temperature

Abstract

© 2019 Hydrogen Energy Publications LLC Shifting chemical looping from high temperatures to intermediate temperatures could mitigate the materials from sintering and benefit for longer durability as well as process economy. However, oxygen carriers cannot perform sufficiently due to the degrading effect at lower temperatures, resulting in the decrease of hydrogen production ability. Although doping precious metals can improve the poor performance at intermediate temperatures, the high cost impeded their large-scale application. In this paper, a range of oxygen carrier materials consisted of earth abundant elements were prepared for chemical looping hydrogen production. The results indicated that CoFe2O4 exhibited the highest hydrogen yield of 11.9 mmol·g−1 and hydrogen production rate of 0.051 mmol g−1·s−1 at 650 °C, which was 1.7 times higher than that of Fe2O3. A combined experimental and DFT calculation method was used to understand the mechanism behind the performance. The results indicated that the synergistic effect between Co and Fe increased the reactivity of the ferrite materials. The enhanced hydrogen production performance was attributed to the high reduction degree and reversible phase change. This study can be also extended to develop more active oxygen carrier for chemical looping processes at intermediate temperatures.