Unraveling the atomic interdiffusion mechanism of NiFe2O4 oxygen carriers during chemical looping CO2 conversion
Unraveling the atomic interdiffusion mechanism of NiFe2O4 oxygen carriers during chemical looping CO2 conversion
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DOI：
10.1002/cey2.493
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发表时间：
2024-02-27
期刊：
影响因子：
20.5
通讯作者：
Li，Fanxing
中科院分区：
文献类型：
--
作者：
Song，Da;Lin，Yan;Li，Fanxing
通过采用金属氧化物作为氧载体，化学链在还原和氧化环境之间转移氧以部分氧化燃料为合成气和将CO2转化为CO方面表现出其有效性。通常，NiFe 2 O 4氧载体在化学链CO2转化中表现出显著的效率。然而，在连续高温氧化还原循环过程中，氧化物氧载体内部结构中原子迁移和演变的复杂过程仍然不清楚。因此，缺乏对与能量转换过程相关的复杂离子迁移和氧转移的基本理解阻碍了高性能氧载体的设计。因此，在这项研究中，我们采用原位表征技术和理论计算，以探讨在H2还原和CO2/实验室空气氧化循环过程中的NiFe 2 O 4氧载体的离子迁移行为和结构演变。我们发现，在H2还原步骤中，晶格氧迅速迁移到空位层，以补充消耗的活性氧物种，而Ni从材料中浸出并迁移到表面。在CO2裂解过程中，Ni向氧载体的中心迁移，形成Fe-Ni合金。在空气氧化步骤中，Fe-Ni向外迁移，由于晶格氧的快速转移引发的Kirkendall效应而产生中空结构。金属原子的迁移路径取决于氧的迁移速率。这些发现突出了调节晶格氧的释放-恢复速率以维持氧载体的结构和反应性的重要性。这项工作提供了一个全面的了解氧化/还原驱动的原子相互扩散行为的氧化氧载体。
By employing metal oxides as oxygen carriers, chemical looping demonstrates its effectiveness in transferring oxygen between reduction and oxidation environments to partially oxidize fuels into syngas and convert CO2into CO. Generally, NiFe2O4oxygen carriers have demonstrated remarkable efficiency in chemical looping CO2conversion. Nevertheless, the intricate process of atomic migration and evolution within the internal structure of bimetallic oxygen carriers during continuous high‐temperature redox cycling remains unclear. Consequently, the lack of a fundamental understanding of the complex ionic migration and oxygen transfer associated with energy conversion processes hampers the design of high‐performance oxygen carriers. Thus, in this study, we employed in situ characterization techniques and theoretical calculations to investigate the ion migration behavior and structural evolution in the bulk of NiFe2O4oxygen carriers during H2reduction and CO2/lab air oxidation cycles. We discovered that during the H2reduction step, lattice oxygen rapidly migrates to vacancy layers to replenish consumed active oxygen species, while Ni leaches from the material and migrates to the surface. During the CO2splitting step, Ni migrates toward the core of the bimetallic oxygen carrier, forming Fe–Ni alloys. During the air oxidation step, Fe–Ni migrates outward, creating a hollow structure owing to the Kirkendall effect triggered by the swift transfer of lattice oxygen. The metal atom migration paths depend on the oxygen transfer rates. These discoveries highlight the significance of regulating the release–recovery rate of lattice oxygen to uphold the structures and reactivity of oxygen carriers. This work offers a comprehensive understanding of the oxidation/reduction‐driven atomic interdiffusion behavior of bimetallic oxygen carriers.