Investigation of micro/nano formation mechanism of porous graphene induced by CO2 laser processing on polyimide film

Laser-induced graphene (LIG) prepared from polyimide (PI) films via a facile CO2 laser-writing technique, has garnered considerable application prospects in micro-supercapacitors, intelligent sensors, and flexible electronics. To achieve the controllable fabrication of LIG, it is essential to understand the micro/nano formation mechanism of LIG. Herein, we explored the micromorphology evolution law, Raman characteristics, primary elements content distribution, and main electron peaks variation of LIG. The experimental results reveal that i) the irradiation region presents a typical crater-like structure accompanied by abundant three-dimensional networks; ii) the low laser power of 3.89 W (9.9 %) is conducive to the formation of high-quality LIG with a small ID/IG; iii) the excessive laser power over 4.15 W (>10 %) provokes element recombination between unstable carbon bonds (C–/C=) and oxygen in the air to reduce the relative carbon content; iv) too high temperature destroys the stability of the graphene structure, resulting in cracks, holes, and defects. Based on the abovementioned findings, we concluded the thermal decomposition process of PI and the local reaction mechanism of LIG. Finally, we realized the controllable fabrication of high-performance LIG with an ultra-small ID/IG (0.3), an extremely high carbon content (94.49 %), and the prominent wetting affinity along with permeability for a water-based electrolyte.