Growth of nano Co encapsulated in carbon-shell

H. Y. Kang, H. Paul Wang, W. K. Lin, I. W. Sun, C. J.G. Jou, U. Ser Jeng, S. G. Chang

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Nanostructured cobalt is one of the key elements in catalysis and therapeutic drug delivery. To design and prepare nanosize-controllable cobalt, a better understanding of its growth mechanism is essential. Growth of Co nanoparticles encapsulated in carbon-shell (Co@C) during temperature-programmed carbonization of the Co2+-β-cyclodextrin (CD) complex at 363-573 K was, therefore, studied by in situ synchrotron small-angel X-ray scattering and X-ray absorption near edge structure spectroscopy. The carbon-shell having a thickness of about 2 nm can prevent the core Co from being aggregated and oxidized. A relatively slow reduction of Co(II) to Co is observed at 393-423 K (stage I) prior to a particle growth transition-state possessing Co of 2.2 nm in diameter at 423-483 K. At 483-513 K (stage II), an increasing Co(II) reduction rate coupled with a rapid fusion and coalescence of Co nanoparticles is found. The average growth rates of Co at stages I and II are about 27 and 98 atoms/min, respectively. The most-probable particle diameter of the ripened Co is 5.9 nm. The carbon-shell can be removed by steam reforming to yield the Co nanoparticles. This work also exemplifies the possible temperature-controllable growth of Co@C, especially in the Co size range of 2-6 nm in diameter.

Original languageEnglish
Pages (from-to)567-572
Number of pages6
JournalJournal of Electron Spectroscopy and Related Phenomena
Volume185
Issue number12
DOIs
Publication statusPublished - 2012 Dec 1

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Radiation
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Spectroscopy
  • Physical and Theoretical Chemistry

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