Tuning porosity and capacitance of laser-assisted grown graphene by controlled thermal annealing
Laser-assisted grown graphene electrodes are promising for electrochemical energy storage, but their performance is limited by poorly controlled pore networks. This study demonstrates that a simple thermal post-treatment effectively tunes porosity and surface chemistry, significantly enhancing capacitive performance. Systematic variation of annealing temperature, dwell time, and atmosphere (air vs. inert) revealed that mild annealing in air up to 500 °C reduces oxygen-containing functionalities and increases the sp2/sp3 carbon ratio. Critically, specific surface area increased from 110 to 498 m² g⁻¹, with a broader pore-size distribution. These structural and chemical changes correlate with an almost order-of-magnitude increase in capacitance compared to untreated electrodes. The optimal condition—400 °C in air for 6 h—yielded electrodes retaining 92% of capacitance at a 25-fold current increase and 99% capacitance retention after 10,000 cycles. Density functional theory (DFT) simulations support a buckling–unknotting mechanism, where metastable interlayer sp3 or C–O–C linkages relax into lower-energy, untied bilayer configurations, reopening pores. This laser-based fabrication combined with thermal annealing offers a scalable, chemical-free route to high-performance graphene electrodes, avoiding wet-chemical activation. The established structure–property relationships provide clear guidance for optimizing related porous carbon architectures.