Structural Study of Polyacrylonitrile-Based Carbon Nanofibers for Understanding Gas Adsorption

Polyacrylonitrile-based carbon nanofibers (PAN-based CNFs) have great potential to be used for carbon dioxide (CO₂) capture due to their excellent CO₂ adsorption properties. The porous structure of PAN-based CNFs originates from their turbostratic structure, which is composed of numerous disordered stacks of graphitic layers. During the carbonization process, the internal structure is arranged toward the ordered graphitic structure, which significantly influences the gas adsorption properties of PAN-based CNFs. However, the relation between structural transformation and CO₂ capture is still not clear enough to tune the PAN-based CNFs. In this paper, we show that, with increasing carbonization temperature, the arrangement of the PAN-based CNF's structure along the stack and lateral directions takes place independently: gradually aligning and merging along the stack direction and enlarging along the lateral direction. Further, we correlate the structural arrangement and the CO₂ adsorption properties of the PAN-based CNFs to propose a comprehensive structural mechanism. This mechanism provides the knowledge to understand and tailor the gas adsorption properties of PAN-based CNFs.