Self‐template porous carbon by direct activation of high‐ash coal liquefaction residue for high‐rate supercapacitor electrodes

Summary Effective utilization of the wasted high‐ash coal liquefaction residue (CLR) becomes increasingly important with the fast development of the coal chemical industry. Herein, a self‐template porous carbon is prepared using CLR as the raw material. The ashes contained in the CLR reacted with potassium hydroxide (KOH), and soluble salts were formed during the heat treatment. After washing, micropores and mesoporous were obtained at the original positions of ashes, while micropores were etched out from the carbon material by KOH. As a result, the carbon substrate with hierarchically porous structure had a maximum surface area of 1787.2 m 2 g −1 , when used as a supercapacitor electrode material, reaching a strong electrical dual‐layer capacitance of 250 F g −1 at 1 A g −1 and maintaining 57% capacitance at 100 A g −1 . The optimized hierarchical porous carbons (HPCs) show small equivalent resistance, high capacitance, and strong period reliability at various charging and discharging rates. HPCs derived from CLR display great potential in supercapacitors, which benefit from plentiful cavity construction, large specific surface area, and high conductivity.