Ruddlesden–Popper Structured Sr ₃ Fe ₂ O _{7− <i>δ</i>} as Redox‐Activated CO ₂ Sorbents for Green Hydrogen Production

Conventional methods for hydrogen production, such as steam methane reforming, face increasing scrutiny due to their reliance on fossil fuels, high CO 2 emissions, and significant capital costs. Sorption‐enhanced steam reforming using renewable feedstocks, where CO 2 is captured in situ, presents a more sustainable alternative. This study investigates the suitability of A‐ and B‐site doped strontium ferrite‐type Ruddlesden–Popper oxides (RPO) as robust CO 2 sorbents, with particular attention on their application in glycerol‐based hydrogen production. Packed bed reactor experiments, complemented by comprehensive characterizations, are systematically conducted to assess and compare the performance of RPO with a stoichiometry of (Sr x Ca 1− x ) 2 Fe 0.9 Ni 0.1 O 4− δ (RPOs) with that of traditional perovskite oxides, that is, Sr x Ca 1− x Fe 0.9 Ni 0.1 O 4− δ (POs), and to unravel the underlying phase transition pathways. Specifically, RPO with a nominal stoichiometry of Sr 1.4 Ca 0.6 Fe 0.9 Ni 0.1 O 4− δ forms an Sr 3 Fe 2 O 7‐ type active phase, exhibiting high H 2 purities (≈95 vol%) coupled with stable CO 2 sorption capacity. Notably, its CO 2 prebreakthrough time is more than six times longer than that of its perovskite counterpart in the sequential Ni‐bed configuration. Finally, the interplay between the reduction and carbonation reactions is examined, highlighting the synergistic benefits that enable the sorbent to fully realize its CO 2 uptake potential.