The Sm-doped Fe₂O₃/CeO₂ is desirable for chemical looping hydrogen generation (CLHG) owing to its satisfactory oxygen ion conductivity, and the reactivity of Fe₂O₃/Ce_0.8Sm_0.2O_1.9 (FSDC20) is the highest among the Sm-doped Fe₂O₃/CeO₂ oxygen carriers with different Sm-doping amounts. This work is focused on the performance evolution of FSDC20 in CLHG with Fe₂O₃/CeO₂ (FSDC0) as comparison, and the related mechanisms are explored. The results show that the evolution of H₂ yield with redox cycles for both samples contain an activation and an attenuation process, and the fourth cycle acts as the demarcation point for FSDC20 before the H₂ yield stabilizes. Specifically, the activation mainly lie in the phase transition from Fe₃O₄ to FeO, and the activation and attenuation processes can be ascribed to the particle microstructure evolution. For the activation process in the first four cycles, the grains on the particle aggregate together, however, with porous structure, and the improved reactivity can be attributed to the enhanced interaction between Fe₂O₃ and CeO₂ as well as the generation of CeFeO₃. However, the grains continue to aggregate on a large scale after the fourth cycle, leading to serious sintering and thus the attenuation process.

中文翻译：

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化学循环制氢中掺 Sm 的 Fe2O3/CeO2 氧载体的演变

Sm掺杂的Fe ₂ O ₃ /CeO ₂由于其良好的氧离子电导率而适用于化学循环制氢（CLHG），其中Fe ₂ O ₃ /Ce _0.8 Sm _0.2 O _1.9 (FSDC20)的反应活性最高在不同Sm掺杂量的Sm掺杂Fe ₂ O ₃ /CeO ₂氧载体中。这项工作的重点是 FSDC20 在 CLHG 中的性能演变，以 Fe ₂ O ₃ /CeO ₂ (FSDC0) 作为比较，并探索相关机制。结果表明，H的演化两个样品的氧化还原循环的₂产率包含激活和衰减过程，并且在 H ₂产率稳定之前，第四个循环充当 FSDC20 的分界点。具体而言，活化主要在于Fe ₃ O ₄到FeO的相变，活化和衰减过程可归因于颗粒微观结构演化。对于前四个循环的活化过程，颗粒上的晶粒聚集在一起，但具有多孔结构，反应性的提高可归因于 Fe ₂ O ₃和 CeO ₂之间的相互作用增强以及 CeFeO 的生成₃. 然而，晶粒在第四次循环后继续大规模聚集，导致严重的烧结和衰减过程。