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Controlling the Surface Oxygen Groups of Polyacrylonitrile-Based Carbon Nanofiber Membranes While Limiting Fiber Degradation

1
Department of Civil and Environmental Engineering, University of Connecticut, Unit 3037, 261 Glenbrook Rd., Storrs, CT 06269-3037, USA
2
Department of Chemistry, University of Connecticut, Unit 3060, 55 N. Eagleville Rd., Storrs, CT 06269-3037, USA
*
Author to whom correspondence should be addressed.
Received: 15 May 2018 / Revised: 22 June 2018 / Accepted: 28 June 2018 / Published: 9 July 2018
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Abstract

Enhancing the performance of nanofibrous carbons requires the specific chemical functionalization of the surface, while limiting material degradation or causing other detrimental changes in the surface area and pore structures. We compare traditional oxidation protocols using HNO3, HNO3/H2SO4, and KMnO4 with the much less used oxidants RuO4 and OsO4, in tandem with secondary oxidants (such as KMnO4 or Oxone®), for their ability to form carboxylic acids on the surface of polyacrylonitrile-based activated carbon nanofiber membrane (ACNF) materials. While the traditional methods increased the carboxylic acid contents, they also destroyed the macrostructure of the ACNF, concomitant with the loss of up to 17 wt.% of the material. RuO4-mediated oxidations proved also to be too harsh. On the contrary, some of the OsO4-based protocols were characterized by very high mass yields; significant increase in carboxylic acid functionalization (6.3 µmol/mg) compared with the unmodified ACNF (1.7 µmol/mg), but with no concomitant loss of macrostructure, as measured by the retention of the Brunauer-Emmett-Teller (BET) surface area; and average pore width. While there was some reduction in micropore volume, the microporosity of the material remained high. The temperature-programmed desorption mass spectrometry (up to 1000 °C) indicated the presence of both single and adjacent carboxylic acid groups. We thus identified mild and highly effective reaction conditions for the functionalization of carbon nanomaterials without undue degradation of their physical properties. View Full-Text
Keywords: activated carbon; electrospun; oxidation; functionalization; carboxylic acid; polyacrylonitrile activated carbon; electrospun; oxidation; functionalization; carboxylic acid; polyacrylonitrile
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Han, Y.; Li, R.; Brückner, C.; Vadas, T.M. Controlling the Surface Oxygen Groups of Polyacrylonitrile-Based Carbon Nanofiber Membranes While Limiting Fiber Degradation. C 2018, 4, 40.

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