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

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 LiCI-KCI molten salt mixture promoted the formation of sheet-like carbon structures. Furthermore, these structures indicated improved crystallinity after annealing at 700 degrees 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 degrees C and 2400 degrees 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 LiCI-KCI salt-treated and non-LiCI-KCI-treated kraft lignin samples.