• Journal of Ceramic Processing Research
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• v.21 no.2
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• pp.148-156
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• 2020

We investigated NiFe2O4/Ce0.9Gd0.1O1.95 (GDC) composites as oxygen carrier materials for chemical looping hydrogen production (CLHP). CLHP is a promising technology to simultaneously capture carbon dioxide and produce hydrogen from fossil fuels. We found that increasing GDC content increased the amount of the hydrogen production of NiFe2O4/GDC composites. Moreover, the oxygen transfer rate for the re-dox reaction increased significantly with increasing GDC content. GDC may affect the reaction kinetics of NiFe2O4/GDC composites. The finely dispersed GDC particles on the surface of NiFe2O4 can increase the surface adsorption of reaction gases due to the oxygen vacancies on the surface of GDC, and enlarge the active sites by suppressing the grain growth of NiFe2O4. The NiFe2O4/15wt% GDC composite showed no significant degradation in the oxygen transfer capacity and reaction rate during several re-dox cycles. The calculated amount of hydrogen production for the NiFe2O4/15wt% GDC composite would be 2,702 L/day per unit mass (kg).

• Journal of Ceramic Processing Research
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• v.20 no.1
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• pp.18-23
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• 2019

Chemical looping combustion (CLC) is a promising carbon capture and storage (CCS) technology whose efficiency and cost primarily relies on the oxygen carrier materials used. In this paper, gadolinium-doped ceria (GDC, Ce0.9Gd0.1O1.95) was added as a promoter to improve the oxygen transfer rate of MgMnO3-δ oxygen carrier materials. Increasing GDC content significantly increased the oxygen transfer rate of MgMnO3-δ-GDC composites for the reduction reaction due to an increase in the surface adsorption of CH4 via oxygen vacancies formed on the surface of the GDC. On the other hand, the oxygen transfer rate for the oxidation reaction decreased linearly with increasing GDC content due to the oxygen storage ability of GDC. Adsorbed oxygen molecules preferentially insert themselves into oxygen vacancies of the GDC lattice rather than reacting with (Mg,Mn)O to form MgMnO3-δ during the oxidation reaction.