Operating chemical looping process at mid-temperatures (550–750 °C) presents exciting potential for the stable production of hydrogen. However, the reactivity of oxygen carriers is compromised by the detrimental effect of the relatively low temperatures on the redox kinetics. Although the reactivity at mid-temperature can be improved by the addition of noble metals, the high cost of these noble metal containing materials significantly hindered their scalable applications. In the current work, we propose to incorporate earth-abundant metals into the iron-based spinel for hydrogen production in a chemical looping scheme at mid-temperatures. Mn 0.2 Co 0.4 Fe 2.4 O 4 shows a high hydrogen production performance at the average rate of ∼0.62 mmol g −1 min −1 and a hydrogen yield of ∼9.29 mmol g −1 with satisfactory stability over 20 cycles at 550 °C. The mechanism studies manifest that the enhanced hydrogen production performance is a result of the improved oxygen-ion conductivity to enhance reduction reaction and high reactivity of reduced samples with steam. The performance of the oxygen carriers in this work is comparable to those noble-metal containing materials, enabling their potential for industrial applications.
Chemical looping hydrogen generation (CLHG) offers a promising solution for producing H 2 from industrial off-gas, such as blast furnace gas. However, increasing H 2 production capacity of the oxygen carrier (OC) at moderate temperature remains a significant challenge. In this study, a novel Cu-Fe-based OC is tailored for moderate-temperature CLHG from blast furnace gas. The results demonstrates that the tailored OC exhibits a superior H 2 production capacity of 12.99 mmol·g −1 at 550 °C, which is 6.5 times higher than that of Fe 2 O 3 at the same temperature. The addition of Cu leads to the formation of oxygen defects, which facilitate the migration of lattice oxygen, thereby the activity of the OC is enhanced. Furthermore, cyclical experiments demonstrates that O 2 -assisted regeneration strategy can effectively suppress the segregation of Cu during the cycling process, and the tailored OC shows good stability during 10 redox cycles. No additional separation process was required and the purity of the hydrogen was higher than 99%. The findings here open a new avenue for efficient CLHG from industrial off-gas at moderate operation temperature.
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