Coal Tar Pitch Preoxidation-Impregnation Regulates Pore Distribution to Prepare Porous Carbon for Electrochemistry

Enhancing the performance of porous carbon materials has become a key focus in current research. In this study, oxygen-containing functional groups were introduced into the carbon skeleton to improve its properties. Air preoxidation can not only introduce oxygen-containing functional groups, but also pretreat coal tar pitch by removing light aromatic components to form a cross-linking network to improve its pore structure. It also helps KOH impregnation to achieve uniform contact with the carbon source, thereby obtaining a uniform pore structure. The optimized material OPC-600 was successfully synthesized. In contrast to preoxidation methods using strong oxidants such as H₂O₂ or HNO₃, which involve safety risks and environmental concerns, the air preoxidation approach is green and straightforward. OPC-600 exhibits a high specific surface area of 2227.93 m²/g and a specific capacitance of 273 F/g at 0.5 A/g. It also demonstrates excellent cycling stability, retaining 95.69% of its capacitance after 10,000 cycles at 5 A/g. The uniform pore structure achieved through KOH impregnation outperformed the carbon material prepared by Yang et al., which showed 93.3% retention under similar cycling conditions. Furthermore, when assembled into a coin cell, the device delivered an energy density of 32.95 Wh/kg at a current density of 1 A/g, surpassing most carbon-based materials reported in the literature. The air preoxidation combined with KOH impregnation produced a porous carbon material with not only a high specific surface area but also a dominant microporous structure, providing abundant sites for efficient charge storage. As a result, OPC-600 exhibits outstanding electrochemical performance. This study provides a novel and efficient strategy for the utilization of coal tar pitch and offers new insights into the design of advanced carbon-based supercapacitors.