Flash Joule heating-driven lignin conversion: Pyrolysis mechanisms and applications of graphitic carbon

• Flash Joule heating efficiently converts lignin into high-value graphitic carbon . • Hydrogen and aromatic monomer yields increase significantly with rising voltage. • Aromatic rings cleave and grow at the edges of microcrystals to form graphene. • Epoxy-LFG composites exhibit high flexural strength and photothermal properties. • The lignin FJH process is low-cost and environmentally friendly. Graphitic carbon is highly valued for its exceptional properties and wide applications; however, the efficient graphitization of lignin remains a significant challenge due to its complex structure. This study investigates the graphitization of lignin driven via flash Joule heating (FJH), providing a comprehensive analysis of the physicochemical structure of the flash graphitic carbon (LFG) and the composition of gaseous and liquid by-products under varying voltages. Additionally, the pyrolysis kinetics and mechanisms of lignin under FJH are explored. The results show that FJH efficiently converts lignin into graphitic carbon, while also generating hydrogen-rich syngas and increased yields of aromatic monomers. Furthermore, using LFG as a filler in epoxy resin significantly enhances the flexural strength and photothermal properties of the composite. This work highlights the potential of the lignin FJH process as an effective and environmentally friendly alternative to traditional methods for producing high-value carbon materials.