Defect Engineering in Laser-Induced Graphene (LIG) Through Temperature Control: A Reactive Molecular Dynamics Study.

Scalable and low-cost graphene synthesis remains a critical challenge for applications in energy storage, sensing, and beyond. Laser-induced graphene (LIG), produced by the rapid local carbonization of polymers like polyimide using laser irradiation, offers a promising route for the one-step, scalable fabrication of porous graphene materials. This work employs reactive molecular dynamics simulations with the ReaxFF force field to investigate the temperature dependence of polyimide carbonization into LIG. We analyze the resulting structures with a focus on the formation of functional groups. Our simulations identify an optimal carbonization temperature window near 3000 K for maximizing graphene yield. Temperatures exceeding 3500 K cause a drastic reduction in six-membered carbon rings, indicative of structural degradation. Conversely, lower temperatures (2500-2750 K) decrease graphene yield but increase the concentration of carbonyl, pyrrolic, pyridinic, and nitrile functional groups. These oxygen- and nitrogen-containing groups are potentially valuable for tailoring functionalized graphene in electrochemical and sensing applications. Furthermore, the graphitization process was found to require extended simulation times (up to ∼5 ns) to reach equilibrium, underscoring the importance of timescale in modeling such processes.