Enhanced ethanol production inside carbon-nanotube reactors containing catalytic particles


Carbon nanotubes (CNTs) have well-defined hollow interiors and exhibit unusual mechanical and thermal stability as well as electron conductivity1. This opens intriguing possibilities to introduce other matter into the cavities2,3,4,5, which may lead to nanocomposite materials with interesting properties or behaviour different from the bulk6,7,8. Here, we report a striking enhancement of the catalytic activity of Rh particles confined inside nanotubes for the conversion of CO and H2 to ethanol. The overall formation rate of ethanol (30.0 mol mol−1Rh h−1) inside the nanotubes exceeds that on the outside of the nanotubes by more than an order of magnitude, although the latter is much more accessible. Such an effect with synergetic confinement has not been observed before in catalysis involving CNTs. We believe that our discovery may be of a quite general nature and could apply to many other processes. It is anticipated that this will motivate theoretical and experimental studies to further the fundamental understanding of the host–guest interaction within carbon and other nanotube systems.

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Figure 1: TEM image and catalytic performance of RMLF-in-CNTs in C2 oxygenate formation.
Figure 2: TEM images and particle size distribution of catalysts and their C2 oxygenate formation activities.
Figure 3: Raman spectra.
Figure 4: Schematic diagram showing ethanol production from syngas inside Rh-loaded carbon nanotubes.


  1. 1

    Dai, H. Carbon nanotubes: Synthesis, integration, and properties. Acc. Chem. Res. 35, 1035–1044 (2002).

    CAS  Article  Google Scholar 

  2. 2

    Ajayan, P. M. et al. Opening carbon nanotubes with oxygen and implications for filling. Nature 362, 522–525 (1993).

    CAS  Article  Google Scholar 

  3. 3

    Seraphin, S., Zhou, D., Jiao, J., Withers, J. C. & Loutfy, R. Yttrium carbide in nanotubes. Nature 362, 503 (1993).

    Article  Google Scholar 

  4. 4

    Tsang, S. C., Chen, Y. K., Harris, P. J. F. & Green, M. L. H. A simple chemical method of opening and filling carbon nanotubes. Nature 372, 159–162 (1994).

    CAS  Article  Google Scholar 

  5. 5

    Guerret-Plécourt, C., Bouar, Y. L., Loiseau, A. & Pascard, H. Relation between metal electronic structure and morphology of metal compounds inside carbon nanotubes. Nature 372, 761–765 (1994).

    Article  Google Scholar 

  6. 6

    Koga, K., Gao, G. T., Tanaka, H. & Zeng, X. C. Formation of ordered ice nanotubes inside carbon nanotubes. Nature 412, 802–805 (2001).

    CAS  Article  Google Scholar 

  7. 7

    Sloan, J. et al. Metastable one-dimensional AgCl1−xIx solid-solution wurzite tunnel crystals formed within single-walled carbon nanotubes. J. Am. Chem. Soc. 124, 2116–2117 (2002).

    CAS  Article  Google Scholar 

  8. 8

    Mühl, T. et al. Magnetic properties of aligned Fe-filled carbon nanotubes. J. Appl. Phys. 93, 7894–7896 (2003).

    Article  Google Scholar 

  9. 9

    Farrell, A. E. et al. Ethanol can contribute to energy and environmental goals. Science 311, 506–508 (2006).

    CAS  Article  Google Scholar 

  10. 10

    Deluca, T. H. Looking at biofuels and bioenergy. Science 312, 1743–1744 (2006).

    CAS  Google Scholar 

  11. 11

    Bhasin, M. M. & O’Connor, G. L. Procede de preparation selective de derives hydrocarbones oxygenes a deux atomes de carbone. Belgian Patent 824822 (1975).

  12. 12

    Planeix, J. M. et al. Application of carbon nanotubes as supports in heterogeneous catalysis. J. Am. Chem. Soc. 116, 7935–7936 (1994).

    CAS  Article  Google Scholar 

  13. 13

    Yoon, B. & Wai, C. M. Microemulsion-templated synthesis of carbon nanotube-supported Pd and Rh nanoparticles for catalytic applications. J. Am. Chem. Soc. 127, 17174–17175 (2005).

    CAS  Article  Google Scholar 

  14. 14

    Girishkumar, G., Hall, T. D., Vinodgopal, K. & Kamat, P. V. Single wall carbon nanotube supports for portable direct methanol fuel cells. J. Phys. Chem. B 110, 107–114 (2006).

    CAS  Article  Google Scholar 

  15. 15

    Zhang, A. M., Dong, J. L., Xu, Q. H., Rhee, H. K. & Li, X. L. Palladium cluster filled in inner of carbon nanotubes and their catalytic properties in liquid phase benzene hydrogenation. Catal. Today 93–95, 347–352 (2004).

    Article  Google Scholar 

  16. 16

    Tessonnier, J., Pesant, L., Ehret, G., Ledoux, M. J. & Pham-Huu, C. Pd nanoparticles introduced inside multi-walled carbon nanotubes for selective hydrogenation of cinnamaldehyde into hydrocinnamaldehyde. Appl. Catal. A 288, 203–210 (2005).

    CAS  Article  Google Scholar 

  17. 17

    Chen, W., Pan, X., Willinger, M., Su, D. & Bao, X. Facile autoreduction of iron oxide/carbon nanotube encapsulates. J. Am. Chem. Soc. 128, 3136–3137 (2006).

    CAS  Article  Google Scholar 

  18. 18

    Chen, W., Pan, X. & Bao, X. Tuning of redox properties of iron and iron oxides via encapsulation within carbon nanotubes. J. Am. Chem. Soc. (2007, in the press, doi:10.1021/ja0713072).

    CAS  Article  Google Scholar 

  19. 19

    Cao, F. et al. Reducing reaction of Fe3O4 in nanoscopic reactors of a-CNTs. J. Phys. Chem. B 111, 1724–1728 (2007).

    CAS  Article  Google Scholar 

  20. 20

    Dujardin, E., Ebbesen, T. W., Hiura, H. & Tanigaki, K. Capillarity and wetting of carbon nanotubes. Science 265, 1850–1852 (1994).

    CAS  Article  Google Scholar 

  21. 21

    Yin, H. et al. Influence of iron promoter on catalytic properties of Rh–Mn–Li/SiO2 for CO hydrogenation. Appl. Catal. A 243, 155 (2003).

    CAS  Article  Google Scholar 

  22. 22

    Hanaoka, T. et al. Ethylene hydroformylation and carbon monoxide hydrogenation over modified and unmodified silica supported rhodium catalysts. Catal. Today 58, 271–280 (2000).

    CAS  Article  Google Scholar 

  23. 23

    de Jong, K. P., Glezer, J. H. E., Kuipers, H. P. C. E., Knoester, A. & Emeis, C. A. Highly dispersed Rh/SiO2 and Rh/MnO/SiO2 catalysts: 1. Synthesis, characterization, and CO hydrogenation activity. J. Catal. 124, 520–529 (1990).

    CAS  Article  Google Scholar 

  24. 24

    Trevino, H., Lei, G. & Sachtler, W. M. H. CO hydrogenation to higher oxygenates over promoted rhodium: Nature of the metal-promoter interaction in RhMn/NaY. J. Catal. 154, 245–252 (1995).

    CAS  Article  Google Scholar 

  25. 25

    Ichikawa, M. & Fukushima, T. Infrared studies of metal additive effects on CO chemisorption modes on SiO2-supported Rh-Mn, -Ti, and–Fe catalysts. J. Phys. Chem. 89, 1564–1567 (1985).

    CAS  Article  Google Scholar 

  26. 26

    Moigno, D., Callejas-Gaspar, B., Gil-Rubio, J., Werner, H. & Kiefer, W. The metal-carbon bond in vinylidene, carbonyl, isocyanide and ethylene complexes. J. Organometal. Chem. 661, 181–190 (2002).

    CAS  Article  Google Scholar 

  27. 27

    von Ahsen, B. et al. Cationic carbonyl complexes of rhodium (I) and rhodium (III): Synthesis, vibrational spectra, NMR studies, and molecular structures of tetrakis(carbonyl) rhodium(I) heptachlorodialuminate and–gallate, [Rh(CO)4][Al2Cl7] and [Rh(CO)4][Ga2Cl7]. Inorg. Chem. 42, 3801–3814 (2003).

    CAS  Article  Google Scholar 

  28. 28

    Kapteijn, F. et al. Alumina-supported manganese oxide catalysts: I. characterization: effect of precursor and loading. J. Catal. 150, 94 (1994).

    CAS  Article  Google Scholar 

  29. 29

    Haddon, R. C. Chemistry of the fullerenes: The manifestation of strain in a class of continuous aromatic molecules. Science 261, 1545–1550 (1993).

    CAS  Article  Google Scholar 

  30. 30

    Ugarte, D., Chatelain, A. & de Heer, W. A. Nanocapillarity and chemistry in carbon nanotubes. Science 274, 1897–1899 (1996).

    CAS  Article  Google Scholar 

  31. 31

    Santiso, E. E. et al. Adsorption and catalysis: The effect of confinement on chemical reactions. Appl. Surf. Sci. 252, 766–777 (2005).

    CAS  Article  Google Scholar 

  32. 32

    Dong, X., Zhang, H., Lin, G., Yuan, Y. & Tsai, K. R. Highly active CNT-promoted Cu–ZnO–Al2O3 catalyst for methanol synthesis from H2/CO/CO2 . Catal. Lett. 85, 237–246 (2003).

    CAS  Article  Google Scholar 

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We thank Z. Tian and W. Weng from Xiamen University China for their help with Raman spectroscopy characterization and A. Goldbach for the discussion. We also acknowledge the financial support of the Natural Science Foundation of China and the Ministry of Science and Technology of China.

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Correspondence to Xinhe Bao.

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The authors declare no competing financial interests.

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Supplementary Information

Supplementary information, figures S1-S6 and table S1 (PDF 4878 kb)

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Pan, X., Fan, Z., Chen, W. et al. Enhanced ethanol production inside carbon-nanotube reactors containing catalytic particles. Nature Mater 6, 507–511 (2007). https://doi.org/10.1038/nmat1916

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