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Carbon spheres for energy applications: Raman and X-ray photoemission spectroscopy studies

Authors

  • Sekhar C. Ray,

    Corresponding author
    1. School of Physics, DST/NRF Centre of Excellence in Strong Materials and Material Physics Research Institute, University of the Witwatersrand, Johannesburg, South Africa
    • Correspondence: Sekhar C. Ray, School of Physics, DST/NRF Centre of Excellence in Strong Materials and Material Physics Research Institute, University of the Witwatersrand, Private Bag 3, WITS 2050, Johannesburg, South Africa.

      E-mail: Sekhar.Ray@wits.ac.za

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  • Zikhona N. Tetana,

    1. DST/NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa
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  • Rudolph Erasmus,

    1. School of Physics, DST/NRF Centre of Excellence in Strong Materials and Material Physics Research Institute, University of the Witwatersrand, Johannesburg, South Africa
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  • Ashish Mathur,

    1. NIBEC, School of Engineering, University of Ulster, Jordanstown, UK
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  • Neil J. Coville

    1. DST/NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa
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SUMMARY

The effect of nitrogen functionalization on the atomic structure of carbon spheres (CSs) with diameters ~55–900 nm, made via direct pyrolysis process, has been studied. The CSs and NCSs were made in a tubular quartz reactor placed either in a vertical furnace or in a horizontal furnace. The chemical bonding in the CSs and NCSs was investigated by means of X-ray photoelectron (XPS) and Raman spectroscopies. XPS studies revealed a decrease in the sp3 bonded carbon sites and an associated increase in the N–sp2C bonding sites after nitrogenation. These results were further confirmed by Raman spectroscopy that showed that the ID/IG ratio increased after N addition to the spheres, indicating a rise in either the number or size of the sp2 clusters. In addition, scanning electron microscopy showed that the spheres, which are >90 at% carbon, consist of concentric graphitic shells. The possible use of CSs in magnetic data storage devices, oxygen reduction reactions, electric double layer capacitors and dye-sensitized solar cells to generate clean and sustainable energy technologies is described. Copyright © 2013 John Wiley & Sons, Ltd.

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