Iron Catalysts for the Growth of Carbon Nanofibers: Fe, Fe3C or Both?
Iron Catalysts for the Growth of Carbon Nanofibers: Fe, Fe3C or Both?
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DOI：
10.1021/cm202315j
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发表时间：
2011-12-27
影响因子：
8.6
通讯作者：
Cojocaru, Costel Sorin
中科院分区：
文献类型：
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作者：
He, Zhanbing;Maurice, Jean-Luc;Cojocaru, Costel Sorin
铁是一种广泛使用的化学气相沉积法生长碳纳米管或碳纳米纤维的催化剂。然而，已经发现Fe和Fe- c化合物（一般为Fe3C）都能催化CNTs/CNFs的生长，但它们各自的催化活性的比较研究仍然缺失。此外，控制铁基催化剂（即α - fe或Fe3C）的晶体结构仍然是一个挑战，这不仅模糊了我们对CNTs/CNFs生长机制的理解，而且还使后续程序复杂化，例如去除催化剂以获得更好的工业应用。在这里，我们展示了在等离子体增强的化学气相沉积反应器中，通过改变生长温度来合成碳基纳米纤维/纳米管，从而部分控制铁催化剂（α - fe或FeC）的相。我们还发现源自Fe3C的CNFs为竹型结构，而源自Fe的CNFs则不是竹型结构。此外，在相同的实验中，我们直接比较了碳基纳米纤维/纳米管的生长速率，发现α - fe纳米颗粒生长的CNFs/CNTs比Fe3C纳米颗粒生长的CNFs更长。分析了催化剂类型对CNFs生长的影响，并根据催化剂的不同相，讨论了相应的生长机制。
Iron is a widely used catalyst for the growth of carbon nanotubes (CNTs) or carbon nanofibers (CNFs) by catalytic chemical vapor deposition. However, both Fe and Fe-C compounds (generally, Fe3C) have been found to catalyze the growth of CNTs/CNFs, and a comparison study of their respective catalytic activities is still missing. Furthermore, the control of the crystal structure of iron-based catalysts, that is alpha-Fe or Fe3C, is still a challenge, which not only obscures our understanding of the growth mechanisms of CNTs/CNFs, but also complicates subsequent procedures, such as the removal of catalysts for better industrial applications. Here, we show a partial control of the phase of iron catalysts (alpha-Fe or FeC), obtained by varying the growth temperatures during the synthesis of carbon-based nanofibers/nanotubes in a plasma-enhanced chemical vapor deposition reactor. We also show that the structure of CNFs originating from Fe3C is bamboo-type, while that of CNFs originating from Fe is not. Moreover, we directly compare the growth rates of carbon-based nanofibers/nanotubes during the same experiments and find that CNFs/CNTs grown by alpha-Fe nanoparticles are longer than CNFs grown from Fe3C nanoparticles. The influence of the type of catalyst on the growth of CNFs is analyzed and the corresponding possible growth mechanisms, based on the different phases of the catalysts, are discussed.