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 1.8nm, mesopores mainly falling in the narrow range of 3.5–4.5nm and macropores, together with high oxygen content (>24.0wt.%). And the HPC based electrodes deliver high volumetric capacitances with a maximum value of 201Fcm−3 at a current density of 5Ag−1, as well as high rate capabilities and excellent cycling stabilities. •HPCs were prepared from coal based humic acid (HA) through a facile KOH activation.•Massive mesopores mainly falling in narrow range of 3.5–4.5nm.•Oxygen content of more than 24.0wt.% in HPCs•High volumetric capacitances with a maximum value of 201Fcm−3 at 5Ag−1•Excellent rate capabilities and cycling stabilities