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The current study reports AxA’1-xByB’1-yO3-𝛿 perovskite redox catalysts (RCs) for CO2-splitting and methane partial oxidation (POx) in a cyclic redox scheme. Strontium (Sr) and iron (Fe) were chosen as A and B site elements with A’ being lanthanum (La), samarium (Sm) or yttrium (Y), and B’ being manganese (Mn), or titanium (Ti) to tailor their equilibrium oxygen partial pressures (P_(O_2 ) s) for CO2-splitting and methane partial oxidation. DFT calculations were performed for predictive optimization of the oxide materials whereas experimental investigation confirmed the DFT predicted redox performance. The redox kinetics of the RCs improved significantly by 1 wt.% ruthenium (Ru) impregnation without affecting their redox thermodynamics. Ru impregnated LaFe0.375Mn0.625O3 (A=0, A’=La, B=Fe, and B’=Mn) was the most promising RC in terms of its superior redox performance (CH4/CO2 conversion >90% and CO selectivity~ 95%) at 800oC. Long-term redox testing over Ru impregnated LaFe0.375Mn0.625O3 indicated stable performance during the first 30 cycles following with a ~25% decrease in the activity during the last 70 cycles. Air treatment was effective to reactivate the redox catalyst. Detailed characterizations revealed the underlying mechanism for redox catalyst deactivation and reactivation. This study not only validated a DFT guided mixed oxide design strategy for CO2 utilization but also provides potentially effective approaches to enhance redox kinetics as well as long-term redox catalyst performance.
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This content will become publicly available on February 1, 2027
LaFe1-xMnxO3−δ as effective redox catalysts for CO2 splitting and methane partial oxidation in a cyclic redox scheme
The current study reports LaFe1-xMnxO3−δ redox catalysts (RCs) for CO2-splitting and methane partial oxidation (CH4-POx) in a cyclic redox scheme. Lanthanum (La) was chosen as the A-site cation whereas iron (Fe) and manganese (Mn) were chosen as the B-site cations, respectively. La, Fe, and Mn were incorporated into the perovskite structure (LaFe1-xMnxO3−δ) at various Fe/Mn ratios to tailor the equilibrium oxygen partial pressures for CO2-splitting and methane partial oxidation. Compared to the standalone redox pairs of Fe and Mn (i.e., Fe2O3/Fe3O4, Fe3O4/FeO, and Mn2O3/Mn3O4) which, from a thermodynamic standpoint, favor the complete combustion of CH4, the perovskite structured redox catalysts (RCs, i.e., LaFe1-xMnxO3−δ) favored the selective oxidation of CH4 to syngas. In addition, impregnating the RCs with 1 wt% ruthenium (Ru) led to a significant improvement in their redox kinetics without affecting their redox thermodynamics. The Ru-impregnated, perovskite structured RCs (i.e., LaFeO3, LaFe0.625Mn0.375O3, and LaFe0.5Mn0.5O3 ) exhibited excellent redox performance in terms of the syngas yield (92 – 100%) and CO2 conversion (95 - 98%). Long-term redox testing over Ru-impregnated LaFeO3 and LaFe0.5Mn0.5O3 demonstrated relatively stable performance for 100 redox cycles whereas activity loss was observed for LaFe0.625Mn0.375O3, LaFe0.375Mn0.625O3, and LaMnO3 respectively. Among RCs containing both Mn and Fe, LaFe0.5Mn0.5O3 exhibited the best performance, maintaining satisfactory activity over 100 cycles and higher oxygen capacity. XRD and XPS analysis suggest that the ability to regenerate the perovskite phase under a CO2 environment and a near surface A:B site cation ratio close to the perovskite stoichiometry would likely correspond to more stable performance. Additionally, the inclusion of Mn on the B-site enhances the coke resistance of the redox catalyst when compared to undoped LaFeO3.
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- PAR ID:
- 10653114
- Publisher / Repository:
- Elsivier
- Date Published:
- Journal Name:
- Catalysis Today
- Volume:
- 462
- Issue:
- C
- ISSN:
- 0920-5861
- Page Range / eLocation ID:
- 115546
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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