Investigation of the Structural Characteristics and Electrical Conductivity of Natural and Synthetic Coal-Derived Graphitic Carbon

Graphitic carbon is highly valuable due to its versatile applications in industry, and coal-derived graphitic carbon represents a significant and abundant resource. Electrical conductivity is a critical parameter for its performance during utilization. In this study, the carbon structural features and electrical conductivity of both naturally graphitized coal series and synthetic series produced by high-temperature treatment were comparatively studied by using X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), etc. Structures of coal-derived graphitic carbon become more ordered with increasing metamorphic degree or pyrolysis temperature. Multiple nanoscale graphitic carbons co-occur within a single sample during graphitization, suggesting that graphitization is not a homogeneous process. The raw anthracite exhibits extremely low electrical conductivity (electrical resistivity is 1.899 × 105 Ω·cm), while electrical conductivity increases quickly as the metamorphic degree increases or when treated with high temperature. However, the electrical conductivity of coal-derived graphite (electrical resistivity is 0.017 Ω·cm for naturally graphitized; 0.141 Ω·cm for pyrolyzed) cannot compare to that of well-crystallized flake graphite (0.004 Ω·cm) and lump graphite (0.008 Ω·cm). The electrical conductivity of naturally graphitized coals is always higher than that of the high-temperature-treated series. Based on the structural and conductivity study of coal-derived graphitic carbon, three factors─graphitization degree, nanoscale pore structure, and packed characteristics of graphitized particles─were found to affect the electrical conductivity of coal-derived graphitic carbon. This study will contribute to the design and development of conductive graphitic carbon materials from coal.