Tracking the evolution of a single composite particle during redox cycling for application in H2 production
Tracking the evolution of a single composite particle during redox cycling for application in H2 production
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DOI：
10.1038/s41598-020-62237-y
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发表时间：
2020-03
影响因子：
4.6
通讯作者：
D. Neagu;E. Papaioannou;Bernhard Tjaden;Xuekun Lu;Cheuk-Man Mak;M. Gaultois;B. Ray;P. Shearing;I. Metcalfe
中科院分区：
文献类型：
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作者：
D. Neagu;E. Papaioannou;Bernhard Tjaden;Xuekun Lu;Cheuk-Man Mak;M. Gaultois;B. Ray;P. Shearing;I. Metcalfe
由金属和金属氧化物相组成的复合材料正在针对各种能量转换应用进行深入研究，这些应用通常期望它们在高温氧化还原条件下运行。对氧化还原循环过程中复合材料演化动力学的了解仍然非常有限，但对于最大限度地提高性能和提高耐用性至关重要。在这里，我们使用多长度尺度 X 射线计算机断层扫描，通过化学循环跟踪单个复合颗粒在 200 个氧化还原循环中的微观结构演变。我们表明，氧化还原循环会引发金属相的离心再分散和孔隙的向心聚集，这两者似乎都是由复合材料中氧交换的不对称性质驱动的。最初，颗粒会形成大量的内部孔隙，从而增强活性，但从长远来看，这会促进结构和成分重组并最终降解。这些结果为氧化还原驱动的微观结构变化以及具有增强耐用性的新型复合材料的设计提供了宝贵的见解。
Composite materials consisting of metal and metal oxide phases are being researched intensively for various energy conversion applications where they are often expected to operate under redox conditions at elevated temperature. Understanding of the dynamics of composite evolution during redox cycling is still very limited, yet critical to maximising performance and increasing durability. Here we track the microstructural evolution of a single composite particle over 200 redox cycles for hydrogen production by chemical looping, using multi-length scale X-ray computed tomography. We show that redox cycling triggers a centrifugal redispersion of the metal phase and a centripetal clustering of porosity, both seemingly driven by the asymmetric nature of oxygen exchange in composites. Initially, the particle develops a large amount of internal porosity which boosts activity, but on the long term this facilitates structural and compositional reorganisation and eventually degradation. These results provide valuable insight into redox-driven microstructural changes and also for the design of new composite materials with enhanced durability.