Potassium citrate assisted synthesis of hierarchical porous carbon materials for high performance supercapacitors

Biomass resources are promising precursors for porous carbon materials attributing to their renewable, plentiful and low-cost characteristics. In this work, hierarchical porous carbon materials are synthesized by carbonizing the mixture of starch rich biomass precursor and potassium citrate. Potassium citrate is vital for the formation of hierarchical porous structure. The specific surface area of carbon material is greatly enhanced with the addition of potassium citrate and gradually increases with the rise of carbonization temperature. APCs-750 obtained from 750 °C displays the best capacitance performance attributing to a high specific surface area (1105.64 m2 g−1) and a high oxygen content (10.25 at.%). APCs-750 exhibits the highest specific capacitance of 242.5 F g−1 at 0.2 A g−1, good rate performance (119.0 F g−1 at 50 A g−1) and excellent stability (retaining 96.5 % after 20,000 cycles). In addition, the symmetric supercapacitor of APCs-750 shows a high energy density of 12.38 Wh kg−1 at the power density of 99.72 W kg−1 and keeps a capacitance retention of 91.3 % after 20,000 cycles. Hence, this work provides a facial strategy to synthesis high capacitance performance hierarchical porous carbon materials from starch rich precursor.