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Creators/Authors contains: "Portillo, Sam"

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  1. 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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    Free, publicly-accessible full text available February 1, 2027