The Role of Oxygen- and Nitrogen-containing Surface Groups on the Sintering of Iron Nanoparticles on Carbon Nanotubes in Different Atmospheres

Authors

  • Dr. Miguel D. Sánchez,

    1. Laboratory of Industrial Chemistry, Ruhr-University Bochum, 44780 Bochum (Germany), Fax: (+49) 234 32 14115
    2. Departamento de Física & Instituto de Física del Sur, Universidad Nacional del Sur—CONICET, 8000 Bahía Blanca (Argentina)
    Search for more papers by this author
  • Peirong Chen,

    1. Laboratory of Industrial Chemistry, Ruhr-University Bochum, 44780 Bochum (Germany), Fax: (+49) 234 32 14115
    Search for more papers by this author
  • Dr. Thomas Reinecke,

    1. Institute of Geology, Mineralogy & Geophysics, Ruhr-University Bochum, 44780 Bochum (Germany)
    Search for more papers by this author
  • Prof. Dr. Martin Muhler,

    1. Laboratory of Industrial Chemistry, Ruhr-University Bochum, 44780 Bochum (Germany), Fax: (+49) 234 32 14115
    Search for more papers by this author
  • Dr. Wei Xia

    Corresponding author
    1. Laboratory of Industrial Chemistry, Ruhr-University Bochum, 44780 Bochum (Germany), Fax: (+49) 234 32 14115
    • Laboratory of Industrial Chemistry, Ruhr-University Bochum, 44780 Bochum (Germany), Fax: (+49) 234 32 14115
    Search for more papers by this author

Abstract

The sintering of iron nanoparticles on carbon nanotubes (CNTs) under different atmospheres was investigated. CNTs were first treated with HNO3 vapor at 200 °C to obtain O-functionalized CNTs (OCNTs). The OCNTs were treated in ammonia at 400 °C to obtain N-doped CNTs (NCNTs). Highly dispersed FeOx nanoparticles were subsequently deposited by chemical vapor deposition from ferrocene under oxidizing conditions. The obtained FeOx/OCNT and FeOx/NCNT samples were allowed to sinter at 500 °C under flowing helium, hydrogen, or ammonia. The samples were studied by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. A significant increase in particle size and a decrease in Fe surface atomic concentration were observed in all the sintered samples. The sintering on OCNTs was more severe than on NCNTs, which can be attributed to stronger metal-substrate interactions and a higher amount of surface defects on NCNTs. The applied gas atmosphere had a substantial influence on the sintering behavior of the nanoparticles: treatment in helium led to the growth of particles and a significant widening of particle size distributions, whereas treatment in hydrogen or ammonia resulted in the growth of particles, but not in the widening of particle size distributions.

Ancillary