A comparison of the charring and carbonisation of oxygen-rich precursors with the thermal reduction of graphene oxide

Abstract

Chars and carbonised chars were produced from two oxygen-rich precursors (Phormium tenax leaf fibres and sucrose crystals) and compared to thermally reduced graphene oxide (TRGO) samples using a range of analytical techniques. A hypothesis that carbonised chars are chemically and nanostructurally more similar to TRGOs than to other proposed structural analogues such as graphites and fullerenes was investigated. The greatest similarities in chemical structural features were observed between the well-carbonised chars and thermally reduced graphene oxide both of which had been prepared using heat treatment temperatures above ≈700 °C. However, thermal analysis and infra-red spectroscopy demonstrated how the char formation process differs from the early stages of the thermal reduction of graphene oxide. Major differences in morphology between TRGOs and various chars were also clearly observable using scanning electron microscopy. Prominent signals indicating the presence of aromatic C–H functional groups were observable in char samples and negligible in the thermally reduced graphene oxide samples when both were analysed by infra-red spectroscopy. The similarities and differences on a nanostructural scale between carbonised chars and thermally reduced graphene oxide are discussed with a focus on clarifying existing models for non-graphitisable carbons produced from oxygen-rich precursors.

Keywords:

• non-graphitisable carbon
• thermally reduced graphene oxides
• chars
• carbonisation

Acknowledgement

The authors thank Steven Newcombe for crafting the quartz vessels required for this work. JM-W was supported by the University of Waikato Doctoral Scholarship. This paper is dedicated to the memory of Michael J. Antal, Jr. Coral Industries Distinguished Professor of Renewable Energy Resources, Hawaii Natural Energy Institute, University of Hawaii at Manoa. October 21st 2015.

Disclosure statement

No potential conflict of interest was reported by the authors.