Kraft lignin-derived carbon sheets produced by molten salt-assisted thermal treatment – Graphitization behavior of the sheet structures

Abstract

The synthesis of high-value carbon materials from lignin-based feedstocks to variable applications has been under intensive research. Production of well ordered crystalline carbon as 2H-graphite has been challenging due to the generally poor graphitizability of lignins. Herein, we produced kraft-lignin-derived carbon materials and studied their graphitization behavior. We show that the use of a LiCl-KCl molten salt mixture promoted the formation of sheet-like carbon structures. Furthermore, these structures indicated improved crystallinity after annealing at 700 °C. This was not observed in the case of kraft-lignin annealed without the presence of a salt mixture. These structures were further thermally post-treated at 1900 °C and 2400 °C in an argon atmosphere by induction annealing to study their graphitization tendency. The high-temperature treatment further emphasized the crystalline structure difference between the LiCl-KCl salt-treated and non-LiCl-KCl-treated kraft lignin samples.