Authors: Jacob W. Martin, Leonard Nyadong, Caterina Ducati, Merilyn Manley-Harris, Alan G. Marshall, and Markus Kraft*

• Gasification charcoal (biochar) was analysed using high resolution mass spectrometry revealing no magic number fullerenes i.e. C₆₀ or C₇₀.
• Heated fullerene arc-carbon also lacked magic number fullerenes but contained oxygenated fragments matching that of charcoal indicating a shared fulleroid-like nanostructure.
• Raman spectroscopy and high resolution transmission electron microscopy supported a stacked, fulleroid-like nanostructure.

In this work, we investigate the molecular composition and nanostructure of gasification charcoal (biochar) by comparing it with heat-treated fullerene arc-soot. Using ultrahigh resolution Fourier transform ion-cyclotron resonance and laser desorption ionization time-of-flight mass spectrometry, Raman spectroscopy, and high resolution transmission electron microscopy we analyzed charcoal of low tar content obtained from gasification. Mass spectrometry revealed no magic number fullerenes such as C₆₀ or C₇₀ in the charcoal. The positive molecular ion m/z 701, previously considered a graphitic part of the nanostructure, was found to be a breakdown product of pyrolysis and not part of the nanostructure. A higher mass distribution of ions similar to that found in thermally treated fullerene soot indicates that they share a nanostructure. Recent insights into the formation of all carbon fullerenes reveal that conditions in charcoal formation are not optimal for the formation of fullerenes, but instead, curved carbon structures coalesce into fulleroid-like structures. Microscopy and spectroscopy support such a stacked, fulleroid-like nanostructure, which was explored using reactive molecular dynamics simulations.

• This paper draws from preprint 219: Nanostructure of Gasification Charcoal (Biochar)
• Access the article at the publisher: DOI: 10.1021/acs.est.8b06861

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