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Direct evidence of active and inactive phases of Fe catalyst nanoparticles for carbon nanotube formation



Stefano Mazzuccoo, Ying Wang, Mihaela M. Tanase, Matthieu C. Picher, Kai Li, Zhijian WU, Stephan Irle, Renu Sharma


Iron and carbon interactions play an important role in various industrial processes such as steel manufacturing, liquid fuel the production by Fischer Tropsch process and carbon nanotube synthesis by chemical vapor deposition process. Interestingly, iron (Fe) nanoparticles act as catalyst for both higher hydrocarbon (liquid fuel) and carbon nanotube synthesis. Despite of a large volume of experimental and theoretical studies reported on catalytic activity of Fe catalyst for either of these reactions, very little is known about the difference between the structure and chemistry of the active and inactive catalytic particles. We have used in situ environmental transmission electron microscopy to elucidate the structure of active and inactive nanoparticles with respect to carbon nanotube formation. We show that two types of iron carbide phases, cementite (Fe3C) and Hägg phase (Fe5C2), form spontaneously under carbon nanotube growth conditions. We present direct evidence that the nanoparticles with Fe3C structure are active in nanotube growth (C-C bond formation), while higher carbon contents renders inactive Fe5C2. Density functional theory calculations suggest that reduced carbon mobility is the leading cause for the catalytic inactivity in the Hägg phase.
Journal of Catalysis


Active and inactive particles, cementite, hagg phase, carbon nanotube synthesis, environmental scanning transmission electron microscopy, in situ, DFT calculations


Mazzuccoo, S. , Wang, Y. , Tanase, M. , Picher, M. , Li, K. , WU, Z. , Irle, S. and Sharma, R. (2014), Direct evidence of active and inactive phases of Fe catalyst nanoparticles for carbon nanotube formation, Journal of Catalysis, [online],, (Accessed April 20, 2024)
Created October 31, 2014, Updated October 12, 2021