Thermodynamic Screening of SrFe ₁₂ O ₁₉ vs Supported Fe ₂ O ₃ Oxygen Carriers for Chemical Looping Reforming with Water Splitting

A comparative thermodynamic analysis of the three-stage CLRWS process (methane reforming, water splitting, and air reoxidation) was performed for iron-based oxygen carriers, including Fe2O3 supported on SiO2, TiO2, MgO, MgAl2O4, and YSZ, alongside the self-supported SrFe12O19. While CH4 conversion and syngas yield were similar, carbon deposition varied significantly, being lowest for SrFe12O19 and Fe2O3/MgAl2O4. Stable phase formation (Fe2SiO4, FeTiO3) on SiO2 and TiO2 limited reduction depth and oxygen availability. SrFe12O19 exhibited the highest metallic iron content, enabling a hydrogen yield of 10.6 mmol/g at >98% purity. Carriers with inert supports (YSZ, MgAl2O4) exhibited classical oxidation, while others formed mixed oxides that could hinder regeneration. All systems required external heat, with the highest demand for YSZ-, MgAl2O4-, and SrFe12O19-based carriers. Steam input variation enabled hydrogen output control and potential autothermal operation. Overall, Fe2O3/MgAl2O4 and SrFe12O19 showed the best potential for CLRWS, combining low carbon deposition, high reversibility, and thermal flexibility.