A ternary Fe-based oxygen carrier with ZrO2-LaFeO3 as support for chemical looping hydrogen generation

Abstract

Fe2O3 is usually supported by inert materials to improve the sintering resistance and redox stability in chemical looping hydrogen generation (CLHG). It is reasonable to apply inert together with perovskite as a composite support for Fe-based oxygen carrier in CLHG. In this work, the Fe2O3/ZrO2/LaFeO3 ternary oxygen carriers were synthesized, and the synergistic effects of ZrO2 and LaFeO3 on the reactivity and redox stability and the intrinsic mechanisms were investigated. The results showed that the 3LF (the mass ratio of LaFeO3 and ZrO2 was 30:10 with Fe2O3 loading at 60 wt %) demonstrated the best hydrogen generation performance with an average H2 yield of 8.3 mmol g-1 and H2 purity of over 99.5%. The LaFeO3 reacted with ZrO2 to form pyrochlore La2Zr2O7 with high melting point, which could be beneficial to the sintering resistance, though it led to the decline of the LaFeO3 quantity. All the cycled samples exhibited a core-shell structure in view of Fe element distribution, owing to the outward migration of Fe cations. The ternary Fe-based oxygen carrier 3LF displayed the most desirable performance in hindering the Fe migration, resulting in enhanced sintering resistance. Furthermore, the high oxygen vacancy concentration in the 3LF facilitated the lattice oxygen transport and hence promoted the reactivity and redox stability in CLHG.