Effect of Activation Process on Electrochemical Properties of Coal Liquefaction Pitch-Based Carbon Foam

Coal liquefaction pitch (CLP) serves as an ideal precursor for carbon materials with high carbon content and an elevated softening point. In this study, activated carbon foam (ACF) based on CLP was synthesized using polyurethane foam as a template, and the effects of activation parameters on the structural characteristics and electrochemical behavior were thoroughly investigated. A typical hierarchical porous reticulated vitreous carbon foam was produced, exhibiting a specific surface area of 592.44 m²·g^–1 and an exceptionally high porosity of 93.95%. Increasing the activation temperature and extending the activation time notably promoted the development of the pore structure. However, these changes also led to an increase in structural disorder and a decrease in graphitization. Higher activation temperatures and prolonged activation times resulted in the depletion of O, N, and S elements, which lowered the wettability and effective contact area of the ACF. Remarkably, intensified activation introduced more oxygen, primarily in the form of C═O and O–H groups, which considerably enhanced the pseudocapacitance. The ACF exhibited a specific capacitance of 117.84 F·g^–1 at 0.5 A·g^–1 in a 6 M KOH electrolyte and maintained 81.11% of its capacitance at 10 A·g^–1. The precursor CLP is more cost-effective and involves a simpler process. The resulting ACF not only provides significant specific capacitance at a relatively low specific surface area but also demonstrates ultralow resistance and exceptional cycling performance. The capacitance retention and Coulombic efficiency in a symmetric supercapacitor were 97% and 95% after 10,000 cycles, respectively. This study provides important insights into the high-value utilization of CLP and the development of high-performance electrode materials.