Layer-Stacking Activated Carbon Derived from Sunflower Stalk as Electrode Materials for High-Performance Supercapacitors

Recently, interest in the use of carbonaceous materials derived from sustainable biomass wastes for supercapacitors (SCs) has grown. The sustainable sunflower stalk is selected as the raw material for preparing activated carbon (AC), using a simple hydrothermal carbonization (HTC) combining an effective activation method. The as-prepared AC sample possesses a unique mesoporous layer-stacking structure which has an unexpected surface area up to 1505 m(2) g(-1) as well as a pore size of 3.6 nm on average. As an electrode material for SCs, the AC demonstrates high electrochemical storage capacity, with the excellent capacitances of 365 and 263 F g(-1) measured by three-electrode and symmetrical SCs systems, respectively. An outstanding capacitance retention rate and a good stability value maintained after 15 000 cycles are close to 81 and 95%, respectively, which are obtained at a current density of 20 A Further, the symmetrical SCs exhibits an energy density as high as 35.7 Wh kg(-1) under the condition of a power density up to 989 W kg(-1). The electrochemical performances of AC derived from sunflower stalk are much higher than that reported in pervious literatures for other biomass. This work provides a clear, simple, and feasible synthetic path and strategy for converting sustainable waste biomass to activated carbons and also demonstrates that the biomass-derived carbon materials have the potential of high electrochemical performance in the field of energy storage, using different natural waste biomass types as raw materials.