CeO 2 -supported Fe 2 O 3 is a satisfactory oxygen carrier for chemical looping hydrogen generation (CLHG). However, the sintering problem restrains its further improvement on redox reactivity and stability. In the present work, a core-shell-structured Fe 2 O 3 /CeO 2 (labeled Fe 2 O 3 @CeO 2 ) oxygen carrier prepared by the sol-gel method was studied in a fixed bed. The effect of the core-shell structure on the sintering resistance and redox performance was investigated with a homogenous composite sample of Fe 2 O 3 /CeO 2 as a reference. The results showed that the Fe 2 O 3 @CeO 2 exhibited much higher redox reactivity and stability than the Fe 2 O 3 /CeO 2 with no CO or CO 2 observed in the generated hydrogen, while the hydrogen yield for Fe 2 O 3 /CeO 2 decreased with redox cycles due to serious sintering. The satisfactory performance of Fe 2 O 3 @CeO 2 can be ascribed to its high sintering resistance, since the core-shell structure suppressed the outward migration of Fe cations from the bulk to the surface of the particles. On the other hand, the migration of Fe cations and their subsequent enrichment on the particle surface led to the serious sintering of Fe 2 O 3 /CeO 2 . The crystallite size evolution of Fe 2 O 3 and CeO 2 in redox cycles further demonstrated the higher sintering resistance of Fe 2 O 3 @CeO 2 . Further, the particle size distribution (PSD) results indicated the agglomeration of Fe 2 O 3 /CeO 2 after cycles. In addition, the CeO 2 shell could facilitate the transport of oxygen ions between the iron oxide nanoparticle core and the shell surface. Therefore, the coating of nanoscale Fe 2 O 3 with a CeO 2 shell did not reduce the redox reactivity and stability of Fe 2 O 3 @CeO 2 , but rather promoted it, though less oxygen-ionic-conductive CeFeO 3 was generated.
Bibliographical noteFunding Information:
This work was supported by the National Key R&D Programme of China ( 2018YFB0605403 ); the National Natural Science Foundation of China ( 51576042 ); and the Natural Science Foundation of Jiangsu ( BK20160672 ).
This work was supported by the National Key R&D Programme of China (2018YFB0605403); the National Natural Science Foundation of China (51576042); and the Natural Science Foundation of Jiangsu (BK20160672).
© 2019 Hydrogen Energy Publications LLC
Copyright 2020 Elsevier B.V., All rights reserved.
- Chemical looping
- Iron oxide