Molecular Dynamics Approach to Formation Mechanism of Sustainable Laser-Induced Graphene from Lignin-Rich Wood

Graphene is a promising material with high thermal and electrical conductivity, but the high energy consumption and the need for toxic chemicals limit its mass production. Wood-derived laser-induced graphene (LIG) has attracted attention as an alternative to synthesizing graphene in an eco-friendly manner without requiring complex chemical treatments. This study examined the formation mechanism of LIG by selecting three representative types of wood based on the lignin content through experiments and ReaxFF molecular dynamics (MD) simulations. Raman spectroscopy showed that the ratio of the D to G peaks (I _D /I _G ) of LIG with a more than 30% lignin content was the lowest at 0.7. MD simulations indicated that the ratio of five- and six-membered carbon rings (r5/r6) decreased to 0.74, and the average surface area increased by up to ≈216%. The sheet resistance measurement yielded the lowest value of ∼236 Ω/sq, indicating an enhancement in electrical conductivity. These results showed that a higher lignin content resulted in the generation of a stable sp² graphitized structure. Spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) showed that the d-spacing of LIG was ∼3.4 Å, indicating a high degree of graphitization. The Cs-STEM images and MD simulation models analyzed at the atomic level showed similar structures. This indicates high consistency between the theoretical model and experimental verification. Moreover, MD simulations are an effective tool for understanding the LIG production process. This research provides a direction for optimizing environmentally friendly and sustainable wood-based LIG, which may contribute to the future development of flexible electronics sensors, electrochemical processes, and catalytic applications.