Atomic Scale Evolution of Graphitic Shells Growth via Pyrolysis of Cobalt Phthalocyanine,Advanced Materials Interfaces

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Atomic Scale Evolution of Graphitic Shells Growth via Pyrolysis of Cobalt Phthalocyanine
Advanced Materials Interfaces ( IF 4.3 ) Pub Date : 2020-09-09 , DOI: 10.1002/admi.202001112
Xiaofang Zhang ₁ , Feng Yang ₂ , Dongliang Tian ₃ , Haofei Zhao ₁ , Rongming Wang ₁ , Woon‐Ming Lau ₁

Affiliation

Nanostructured graphitic‐layer‐materials with precise control of the layer‐nanostructure, are known to surpass many benchmarks in electrical, optical, and mechanical properties. The development of such controlled synthesis is, however, stalled by the difficulty in tracking the exact growth mechanism and dynamics of the layer‐structure. Herein, the growth mechanism of onion‐like graphitic‐layer‐structures with an atomic precision is revealed by pyrolysis in an aberration‐corrected environmental transmission electron microscopy (ETEM). Specifically, the time‐evolution of cobalt phthalocyanine (CoPc), bearing better contact between carbon atoms and metamorphosizing a graphitization‐catalyst, at 850°C in an ETEM are tracked to an intriguing Co‐Co₃C nanocore enveloped by several graphitic layers. The growth dynamics of this onion‐like graphitic shell comprises, rather unexpectedly, out‐diffusion of carbon atoms from the core to fuel the growth of new outermost shell‐layers, plus lateral/inwards and intrashell/intershell diffusion of carbon atoms to amend shell‐defects. Thus, unusual dynamics of seemingly contracting shell‐expansion and shell‐consolidation is revealed, with the surprising phenomenon of a decrease in the number of atomic shell‐layers in exchange for layer‐perfectness towards the end of the controlled synthesis. These results indicate pyrolysis of an organometallic compound in an ETEM is a paradigm for understanding and developing controlled synthesis of novel high‐quality graphitic‐layer‐materials.

中文翻译：

钴酞菁热解对石墨壳生长的原子尺度演化

可以精确控制纳米层结构的纳米石墨层材料在电气，光学和机械性能方面已超过许多基准。但是，由于难以追踪层结构的确切生长机理和动力学，因此这种受控合成的发展停滞了。在此，通过像差校正环境透射电子显微镜（ETEM）的热解揭示了具有原子精度的洋葱状石墨层结构的生长机理。特别是，在850°C的ETEM中，碳原子之间具有更好的接触以及石墨化催化剂变质的钴酞菁（CoPc）的时间演化被追踪到了有趣的Co-Co _3。C纳米芯被数个石墨层包围。这种洋葱状石墨壳的生长动力学出乎意料地包括碳原子从核中的向外扩散，以推动新的最外层壳层的生长，以及碳原子的横向/向内和壳内/壳内扩散，以修正壳层。缺陷。因此，揭示了看似收缩的壳膨胀和壳固结的异常动力学，并伴随着令人惊讶的现象，即原子壳层的数量减少，从而在受控合成的最后阶段换来了层的完美性。这些结果表明，有机金属化合物在ETEM中的热解是理解和开发新型高质量石墨层材料受控合成的范例。

更新日期：2020-09-09

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