Structural Engineering of Nanocarbons Comprising Graphene Frameworks via High-Temperature Annealing

Abstract

Abstract High-temperature annealing is an effective way to heal the defects of graphene-based nanocarbons and enhance their crystallinity. However, the thermally induced vibration of the graphene building blocks often leads to unfavorable micro-, nano-structural evolution including layer stacking. Herein, the key structural factors to achieve highly crystalline graphene frameworks with desired microstructures upon annealing at 1800 °C is revealed. The structural changes of fullerenes, single-walled carbon nanotubes, and graphene-based porous frameworks are precisely analyzed by their structural parameters, such as the total number of graphene edge sites and precise graphene stacking structures, using a novel advanced vacuum temperature-programmed desorption technique up to 1800 °C. The stacked structure is differentiated into loose and tightly stacking, where the loosely stacked structure is found to induce further stacking at high-temperature. Moreover, a graphene framework with an inner space size of greater than 4–7 nm is beneficial to avoid structural change upon high-temperature annealing. These findings offer both a fundamental understanding of the solid-state chemistry of nanocarbons under high temperatures and a viable strategy for engineering edge-site free graphene frameworks with pre-designed microstructures.