Hierarchical porous active carbon from fallen leaves by synergy of K2CO3 and their supercapacitor performance

The active carbon materials (ACs) derived from fallen leaves (FLs) are prepared by the activations of mixed KOH and K2CO3. Characterizations reveal that the use of single activator KOH creates the most of micropores in three dimensional and K2CO3 produces the mesopores/macropores mostly in shallow. When combining KOH with K2CO3, the pore size of ACs is enlarged. The surface areas and hierarchical pore structures are related to the mass ratio of two activators. The electrochemical properties are monitored with the cyclic voltametry, charging-discharging and electrical impedance spectra. The prepared sample displays high specific capacitance of up to 242 F g−1 (0.3 A g−1, 6 M KOH) in a two-electrode system. Their good cycling stability with nearly no capacitance decrease is obtained after 2000 cycles.