Chemical Looping Reforming of Methane Coupled with CO2 Splitting Using a Sol–Gel-Derived LaFe0.4Co0.6O3 Oxygen Carrier

Abstract

Chemical looping reforming of CH₄ coupled with CO₂ splitting (CLRCS) is an attractive technology that enables covalorization of CO₂ and CH₄ to high- value syngas. In CLRCS, oxygen carriers shuttle oxygen from CO₂ to CH₄, enabling selective methane partial oxidation and CO₂ splitting. However, rational optimization of perovskite oxygen carriers is pivotal to advancing this technology. Herein, a set of Co-doped LaFeO₃ perovskite oxygen carriers (LaFe_1–xCo_xO₃, x = 0–1) were synthesized via an optimized sol–gel method. The catalytic performances of materials were measured in a fixed-bed reactor at 750–950 °C, complemented by X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations for structural analysis. Among all tested samples, LaFe_0.4Co_0.6O₃ achieves superior performance at 850 °C, with 92% CH₄ conversion and ∼90% syngas selectivity (H₂/CO ≈ 2). Moderate Co incorporation remodels the Fe-centered perovskite lattice, which appeared to tune the material redox properties. By contrast, excessive Co doping (x > 0.6) deteriorates regeneration capacity and cyclic stability. Catalytic behavior is highly sensitive to the oxidant atmosphere: CO₂ and H₂O as mild oxidants are hypothesized to preserve the oxygen carrier in a favorable incompletely oxidized state for selective reforming, whereas O₂ causes overoxidation, restricting CH₄ conversion to 60% and syngas selectivity to 10%. Moreover, optimizing the inlet CO₂ concentration further modulates the redox state of LaFe_0.4Co_0.6O₃. Benefiting from optimized oxidation protocols, the material retained steady performance over 100 redox cycles, sustaining 96–98% CH₄ conversion, 92.9–95.4% CO selectivity, 93.9–96.8% H₂ selectivity, and 91–93% CO₂ utilization efficiency. This study proposes plausible design guidelines for perovskite oxygen carriers tailored to sustainable syngas synthesis via CLRCS and provides fundamental structural and operational references for future reactor scale-up and renewable-energy matching of this carbon capture process.