NiFe 2 O 4 oxygen carrier (OC) presents higher oxygen carrying capacity than single metal oxides (NiO and Fe 2 O 3 ). However, the redox ability of NiFe 2 O 4 gets deactivated due to phase segregation. Herein, the investigation of the effect of supports (CeO 2 , CeZrO 2 , and ZrO 2 ) on the phase stability and the redox performance of NiFe 2 O 4 during the chemical looping (CL) process are presented. The structure of NiFe 2 O 4 -based OCs is characterized using different characterization methods. The CL reaction is conducted in a fixed-bed reactor at 900 °C under alternate 5% CO/N 2 and 5% O 2 /N 2 atmospheres. The results indicate that the redox performance and the phase stability of NiFe 2 O 4 -based OCs are significantly affected by the supports. According to experimental results, CeO 2 can improve the oxygen mobility of NiFe 2 O 4 . The CeO 2 –NiFe 2 O 4 OC has the best performance in terms of both recyclability and phase stability during the redox cycles. The results show that CeO 2 –NiFe 2 O 4 can reduce the tendency of Fe segregation due to the high concentration of oxygen vacancies. It can be reduced and reoxidized to the original crystalline phase of NiFe 2 O 4 . Nevertheless, the CeZrO 2 –NiFe 2 O 4 and ZrO 2 –NiFe 2 O 4 OCs have drawbacks related to serious sintering and phase segregation into Fe 2 O 3 .
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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