Dual-role KCl-assisted fabrication of porous carbon with controllable architecture from coal liquefaction residue for supercapacitors

Preparation of high-performance electrode materials in a low-cost and simple way is of great significance for the application and development of supercapacitors. Herein, a dual-role KCl-assisted KOH activation method with low KOH consumption was employed to fabricate porous carbons with controllable architecture, using the coal liquefaction residue (CLR) as the raw material. It is indicated that KCl not only serves as an auxiliary template for pore-forming but also contributes to an enhancement in the melting of K2CO3, an intermediate of KOH activation, resulting in an improvement in the efficiency of KOH activation. As a consequence, the prepared samples possess highly developed pore structure even at a low KOH consumption, which endow them with excellent capacitive performance. The as-fabricated optimal porous carbon (LR-KPC-4) displays a maximum specific capacitance of 375 F g−1 at 0.5 A/g and superior rate capacity, which are much better than those of the porous carbon prepared without KCl. The fabricated symmetric supercapacitor shows a high specific capacitance of 256 F g−1 at 0.5 A/g, energy density of 8.9 Wh kg−1 at 125 W kg−1 and great cycling stability. This work demonstrates a facile strategy to efficiently convert CLR into porous carbons for high-performance supercapacitors. Meanwhile, it paves a promising way for value-added utilization of CLR.