Na-β-Al2O3 stabilized Fe2O3 oxygen carriers for chemical looping water splitting: correlating structure with redox stability

08 December 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Chemical looping is an emerging technology to produce high purity hydrogen from fossil fuels or biomass with the simultaneous capture of the CO2 produced at the distributed scale. This process requires the availability of stable Fe2O3-based oxygen carriers. Fe2O3-Al2O3 based oxygen carriers exhibit a decay in the H2 yield with cycle number due to the formation of FeAl2O4 that cannot be re-oxidized. In this study, the addition of sodium (via a sodium salt) in the synthesis of Fe2O3-Al2O3 oxygen carriers was assessed as a means to counteract the cyclic deactivation of the oxygen carrier. Detailed insight into the oxygen carrier’s structure was gained by combined X-ray powder diffraction (XRD), X-ray absorption spectroscopy (XAS) at the Al, Na and Fe K-edges and scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (STEM/EDX) analyses. The addition of sodium prevented the formation of FeAl2O4 and stabilized the oxygen carrier via the formation of a layered structure, Na-β-Al2O3 phase. The resulting material, Na-β-Al2O3 stabilized Fe2O3, showed a very high H2 yield of ca. 13.3 mmol/g during 15 cycles.


water splitting
oxygen carrier
chemical looping
X-ray absorption spectroscopy


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