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Abstract This short review examines solid reaction mediums—specifically oxygen, CO₂, and carbon carriers—within the framework of Chemical Looping (CL) to illuminate various CO₂utilization pathways. The thermodynamic consideration for carrier selection is first discussed. This is followed by a summary of the key carrier types investigated to date, with an emphasis on elucidating the roles of compositional, structural, and surface properties of the various carriers toward their reactive performances. Besides assessing the performances of various oxygen carriers, their long-term performance, potential deactivation mechanism in the presence of CO_2,and strategies for their reactivation are also discussed in the context of chemical looping dry reforming of methane (CLDRM). While relatively underexplored, the current status of development, advantages, and potential limitations of CO₂carriers in sorbent looping dry reforming of methane (SLDRM) and carbon carriers in chemical looping methane cracking (CLMC) are also reviewed and discussed. Emerging topics such as combined carriers are also covered along with a perspective for future research directions. Overall, this review aims to offer insights into the sustainable use of CO₂through chemical looping, emphasizing the potential of solid reaction mediums across different carriers and the challenges associated with these solid reaction mediums. 

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. 

High-throughput computational screening and machine learning accelerate the rational design of mixed metal compounds for diverse chemical looping applications, transforming materials discovery from trial-and-error to data-driven approaches.