Oxygen-rich and hierarchical porous carbons prepared from coal based humic acid for supercapacitor electrodes

Hierarchical porous carbons (HPCs) were prepared from coal-derived humic acid (HA) through a facile KOH activation method and used as electrode materials for supercapacitors. The obtained HPCs possess hierarchical porous structure consisting of micropores less than 1.8 nm, mesopores mainly falling in the narrow range of 3.5-4.5 nm and macropores, together with high oxygen content (> 24.0 wt.%). And the HPC based electrodes deliver high volumetric capacitances with a maximum value of 201 F cm− 3 at a current density of 5 A g− 1, as well as high rate capabilities and excellent cycling stabilities.