Three-dimensional flower-like and hierarchical porous carbon materials as high-rate performance electrodes for supercapacitors

Three-dimensional flower-like and hierarchical porous carbon material (FHPC) has been fabricated through a simple and efficient carbonization method followed by chemical activation with flower-like ZnO as template and pitch as carbon precursor. The hierarchical porous structure is composed of numerous micropores and well-defined mesopores in the interconnected macroporous walls. The FHPC electrode can achieve a relatively high capacitance of 294 F g−1 at a scan rate of 2 mV s−1 and excellent rate capability (71% retention at 500 mV s−1) with superior cycle stability (only 2% loss after 5000 cycles) in 6 mol L−1 KOH electrolyte. The symmetric supercapacitor fabricated with FHPC electrodes delivers a high energy density of 15.9 Wh kg−1 at a power density of 317.5 W kg−1 operated in the voltage range of 0–1.8 V in 1 mol L−1 Na2SO4 aqueous electrolyte.