Microporous carbons with three-dimensional interconnected macropores based on corn stigmas for advanced supercapacitors

The slender corn stigmas-based microporous carbon (denoted as ACS-22) was prepared by the pre-treatment of corn stigmas in KOH solution and subsequent activation process. The resulted ACS-22 exhibits high specific surface area (1602 m2 g−1), 3D interconnected macroporous cores, and large percentage of micropores. When used as electrode in supercapacitors, the interconnected macropores can serve as ion-buffering reservoirs and facilitate transportation of electrolyte ions, while abundant micropores can provide electrode with a high accessible surface area for ion storage. Therefore, ACS-22 presents high capacitance and excellent rate capability. For example, the capacitance of ACS-22 can reach 210 F g−1 at 0.1 A g−1, which slightly decreases to 190 F g−1, giving a capacitance retention of 90%. Furthermore, ACS-22 also shows good cyclic stability that even after 10000 cycles, 97% capacitance can still remain.