Hierarchical porous carbon derived from Gardenia jasminoides Ellis flowers for high performance supercapacitor

Low cost and high performance electrode materials are essential for the development of sustainable energy conversion and storage systems. Herein, we report on the preparation of hierarchical porous carbon for high performance supercapacitor by using the flowers of Gardenia jasminoides Ellis (GE) as the biomass precursor. The GE flowers were firstly pre-carbonized at moderate conditions, and then hydrothermally treated in the presence of KOH. After the final simultaneous activation and carbonation at high temperature, hierarchical porous carbon with large specific surface area was obtained. Electrode based on the porous carbon offers a high specific capacitance (255 F g−1 at 0.5 A g−1), excellent rate capability and cycling stability (98.3% capacitance retention after 20,000 cycles) in 6 M KOH aqueous solution in a three-electrode system. Furthermore, symmetric supercapacitor with aqueous electrolyte provides a high specific capacitance of 153.7 F g−1 at 0.5 A g−1 and an energy density of 5.2 Wh kg−1 at power density of 246.9 W kg−1. The study demonstrated an efficient and sustainable approach for high performance supercapacitors by using biomass waste carbon.