Modulating Oxygen Transfer via A-Site Doping in LaFeO3 for Coke-Resistant Chemical Looping Steam Methane Reforming

Abstract

Chemical looping steam methane reforming (CL-SMR) is a promising technology for the simultaneous production of high-purity hydrogen and syngas without the need for external gas separation units. This study evaluates a series of A-site doped perovskite-type oxygen carriers, La0.8A0.2FeO3 (A = Ca, Sr, Ba), to investigate the influence of alkaline earth metal doping on redox behavior and catalytic performance in CL-SMR. Substituting divalent cations at the A-site effectively promotes oxygen vacancy formation and enhances lattice oxygen transfer. Among the evaluated oxygen carriers, Sr-doped LaFeO3 (La0.8Sr0.2FeO3) exhibits the most favorable performance. This is attributed to the optimal concentration of oxygen vacancies, which improved oxygen transfer, as confirmed by X-ray photoelectron spectroscopy, cerimetric titration, and O2-temperature programmed desorption. While undoped LaFeO3 (LF) exhibits the highest methane activation, its limited oxygen mobility leads to severe coke formation. Enhanced oxygen transfer in La0.8Sr0.2FeO3 effectively suppresses carbon deposition, while it shows the highest CO and hydrogen production. It achieves consistently high CO and H2 yields (6.22–6.51 and 6.48–6.69 mmol/gcat, respectively) and demonstrates excellent stability over 50 redox cycles.