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Conventional methods for hydrogen production, such as steam methane reforming, face increasing scrutiny due to their reliance on fossil fuels, high CO2emissions, and significant capital costs. Sorption‐enhanced steam reforming using renewable feedstocks, where CO2is captured in situ, presents a more sustainable alternative. This study investigates the suitability of A‐ and B‐site doped strontium ferrite‐type Ruddlesden–Popper oxides (RPO) as robust CO2sorbents, with particular attention on their application in glycerol‐based hydrogen production. Packed bed reactor experiments, complemented by comprehensive characterizations, are systematically conducted to assess and compare the performance of RPO with a stoichiometry of (SrxCa1−x)2Fe0.9Ni0.1O4−δ(RPOs) with that of traditional perovskite oxides, that is, SrxCa1−xFe0.9Ni0.1O4−δ(POs), and to unravel the underlying phase transition pathways. Specifically, RPO with a nominal stoichiometry of Sr1.4Ca0.6Fe0.9Ni0.1O4−δforms an Sr3Fe2O7‐type active phase, exhibiting high H2purities (≈95 vol%) coupled with stable CO2sorption capacity. Notably, its CO2prebreakthrough time is more than six times longer than that of its perovskite counterpart in the sequential Ni‐bed configuration. Finally, the interplay between the reduction and carbonation reactions is examined, highlighting the synergistic benefits that enable the sorbent to fully realize its CO2uptake potential.
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Effect of R-site element on crystalline phase and thermal stability of Fe substituted Mn mullite-type oxides: R 2 (Mn 1−x Fe x ) 4 O 10−δ (R = Y, Sm or Bi; x = 0, 0.5, 1)
Combining experimental and theoretical studies, we investigate the role of R-site (R = Y, Sm, Bi) element on the phase formation and thermal stability of R 2 (Mn 1−x Fe x ) 4 O 10−δ ( x = 0, 0.5, 1) mullite-type oxides. Our results show a distinct R-site dependent phase behavior for mullite-type oxides as Fe is substituted for Mn: 100% mullite-type phase was formed in (Y, Sm, Bi) 2 Mn 4 O 10 ; 55% and 18% of (Y, Sm) 2 Mn 2 Fe 2 O 10−δ was found when R = Y and Sm, respectively, for equal Fe and Mn molar concentrations in the reactants, whereas Bi formed 54% O10- and 42% O9-mixed mullite-type phases. Furthermore, when the reactants contain 100% Fe, no mullite-type phase was formed for R = Y and Sm, but a sub-group transition to Bi 2 Fe 4 O 9 O9-phase was found for R = Bi. Thermogravimetric analysis and density functional theory (DFT) calculation results show a decreasing thermal stability in O10-type structure with increasing Fe incorporation; for example, the decomposition temperature is 1142 K for Bi 2 Mn 2 Fe 2 O 10−δ vs. 1217 K for Bi 2 Mn 4 O 10 . On the other hand, Bi 2 Fe 4 O 9 O9-type structure is found to be thermally stable up to 1227 K. These findings are explained by electronic structure calculations: (1) as Fe concentration increases, Jahn–Teller distortion results in mid band-gap empty states from unstable Fe 4+ occupied octahedra, which is responsible for the decrease in O10 structure stability; (2) the directional sp orbital hybridization unique to Bi effectively stabilizes the mullite-type structure as Fe replaces Mn.
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- Award ID(s):
- 1700030
- PAR ID:
- 10062589
- Date Published:
- Journal Name:
- RSC Advances
- Volume:
- 8
- Issue:
- 1
- ISSN:
- 2046-2069
- Page Range / eLocation ID:
- 28 to 37
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1039/C7RA09699B
