Changing the potassium-based activation path to prepare coal-based porous carbon with more graphitic or graphene structures for high-performance organic supercapacitors

Abstract

Graphitic porous carbon is becoming an excellent platform for high-performance supercapacitors due to its unique structural characteristics, especially the combination of high specific surface area and long-range ordered sp2 carbon framework, which can synergistically improve the ion transfer/storage capability and the structural stability during long-term cycling. However, the trade-off contradiction between porosity and graphitization of carbon materials is difficult to circumvent by traditional chemical or physical activation strategies. Herein, we changed the conventional potassium-based activation pathway by introducing a pre-carbonization process, thus transforming low-rank coal precursors into graphitic porous carbon with more graphite or graphene structures. Raman mapping characterization was introduced to comprehensively reveal the distribution of crystalline carbon within the obtained carbon materials, confirming that enhancing the structural maturity of carbon-based precursors by introducing a pre-carbonization process promotes the deep and uniform development of graphitized structures during the KOH activation process. Typical reaction intermediate characterization indicates that the reason for this structural transformation is due to a change in the primary form of potassium species under the changed activation pathways, leading to a solid-liquid phase reaction environment mediated by molten K2CO3. The obtained graphitic porous carbon possesses simultaneously a hierarchically porous structure with specific surface area of 2456 m2 g−1 and well-developed graphitic carbon crystalline by which the constructed organic supercapacitor delivers excellent capacitance and rate performance, along with a high energy-power density, and a lifespan exceeding 10,000 cycles. The elucidated potassium-based activation mechanism facilitates the easy adjustment of carbon porosity and crystalline structures to meet varying requirements in different application scenarios.