Effect of copper dopant on the mixed cobalt-iron oxides for hydrogen generation via chemical looping redox cycles

• Published in: International journal of hydrogen energy 2020-10, Vol.45 (53), p.28372-28382
• Main Authors: Xiong, Yingwei, Zhao, Jun, Zheng, Zhiqin, Li, Wenli
• Format: Article
• Language: English
• Subjects: Chemical looping; Hydrogen generation; Mid-temperature; Oxygen carriers
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.07.245

The long-term stability of oxygen carriers can be significantly improved by operating chemical looping at mild conditions, enabling the potential for large-scale applications. However, the diminished temperature has a detrimental effect on the kinetics, resulting in the decreased chemical looping performance. Although doping of noble metals can promote the performance of oxygen carriers at mid-temperatures, the high cost significantly impeded the scalable use of these oxygen carriers. Here we report the use of copper to dope mixed cobalt-iron oxides as oxygen carriers for hydrogen generation via chemical looping redox cycles. Cu0.25Co0.75Fe2O4 shows satisfactory hydrogen yield (~9.39 mmol g−1) and average hydrogen generation rate (~0.47 mmol g−1 min−1) with high stability over 20 redox cycles at 550 °C. The characterizations substantiate that the improved performance is a consequence of Cu to enhance the oxygen-ion conductivity through the bulk and promote the reactivity of the oxygen carriers with reactant gases on the surface. The performance of the samples in this work is comparable to those contains noble metals. [Display omitted] •Cu dopant improves the oxygen diffusion through the bulk.•Cu dopant enhances the redox reactions on the surface.•High hydrogen performance is obtained by Cu0.25Co0.75Fe2O4 at 550 °C.