Atomic Scale in-situ Studies of Catalytic Reactions between Iron Clusters and Single-walled Carbon Nanotubes

Kecheng Cao(1), Johannes Biskupek (1), Thomas W. Chamberlain(2), Andrei N. Khlobystov (2) and Ute Kaiser (1)

(1) Electron Microscopy of Materials Science, Central Facility for Electron Microscopy, Ulm University, Albert Einstein Allee 11, Ulm 89081, Germany

(2) School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom

Metal nanoparticle catalysts play an important role in the field of catalytics. Understanding the reaction between metal nanoparticles (MNPs) and carbon at the atomic scale contributes to the design of highly efficient catalysts. Single-walled carbon nanotubes (SWNTs) with the characteristics of heat resistance, cleanness and transparency areideal nano-test tubes for MNPs to study their catalytic properties in-situ. Moreover, with the aid of the powerful aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM), several kinds of MNPs are filled into SWNT and have been investigated their reactions with SWNT.The transition metals are varied along groups as well as periods of the periodic table of elements, and characterized systematically to track their interactions with the electron beam and the carbon special environment^1-4. Among them, Os and Ni nanoparticles exhibit the ability of cutting SWNT under electron beam irradiation^{2, 3}. But iron nanoparticles with Fe₃C structure are much more stable that no significant reactions are observed between Fe₃C and SWNT⁴.

In this study we present in-situ irradiation experiments of sub-nanometer sized α- Fe clusters enclosed in SWNTs by means of low-voltage AC-HRTEM. The Fe nanoparticles show different structure to the previously published experiments on Fe₃C nanoparticles⁴, and are observed to be unstable under e-beam irradiation at 80 kV. In our experiments, the particular technique of HRTEM combines imaging tool and irradiation source in one integral experiment. Here, SWNTs are initially filled with Fe₃(CO)₁₂ molecules and then irradiated by election-beam with acceleration voltage 80 kV in TEM. α- Fe nanoparticles are obtained in the lumen of SWNTs. Being irradiated, α- Fe nanoparticles keep changing shape and restructuring the geometric construction of SWNT and ultimately cut it into two parts. Additional experiments regarding the stability under e-beam irradiation at much lower voltages down to 20 kV will be carried out to study influences of knock-on damage and ionization effects. Figure 1 shows a time series of the cutting process. . Thus we confirm that two kinds of clusters, α- Fe nanoparticle and Fe₃C can be obtained by breaking the Fe₃(CO)₁₂ molecules in SWNT and they exhibits distinct catalytic activities that Fe₃C is stable but α- Fe nanoparticle can cut SWNTs. The experiments were conducted using a C_S-corrected FEI Titan 80-300 operated at 80 kV. The dose rate was 1.4*10⁶ e^–/s*nm² and the exposure time was 1.0 second.

[1] Thilo Zoberbier et.al. J. Am. Chem. Soc. 134, 3073−3079 (2012)

[2] Thomas W. Chamberlain et.al. Chem. Sci. 3, 1919–1924 (2012)

[3] Irina V. Lebedeva et.al. Naoscale, 6, 14877-14890 (2014)

[4] Thilo Zoberbier et.al. Small, DOI: 10.1002/smll.201502210 (2016)

Acknowledgment

We gratefully acknowledge the support of the “Graphene Flagship”, DFG SPP “Graphene”, the DFG and the Ministry of Science, Research and the Arts (MWK) of Baden–Wuerttemberg within the frame of the SALVE ( Sub Angstrom Low-Voltage Electron Microscopy ) project, ERC Consolidator Grants and EPSRC and NUST “MISiS” (grant K3-2015-030) for financial support.

Figures:

Figure 1. The time-series shows the stages of the interaction between a Fe nanocluster and SWNT inner sidewall induced by the electron-beam imaged by AC-HRTEM at 80 keV. On the right column are the corresponding structural diagrams.

« Back to The 16th European Microscopy Congress 2016

EMC Abstracts - https://emc-proceedings.com/abstract/atomic-scale-in-situ-studies-of-catalytic-reactions-between-iron-clusters-and-single-walled-carbon-nanotubes/