Mesopore-rich carbon flakes derived from lotus leaves and it’s ultrahigh performance for supercapacitors

Much attractions have been aroused about the biomass-derived carbon used for energy storage due to their high specific surface areas (SSA) and well-developed porosity. Here, we report a novel biomass carbon derived from lotus leaves which has excellent electrochemical performance. A two-step activation method is used for the preparation of the final sample: double activated lotus carbon (DALC). Briefly, HNO3 is used for the first-step activation and the KOH activating process continues. The DALC possesses an ultra-high SSA of 2351 m2 g−1 and abundant micropores and mesopores structures. And importantly, some defects are fabricated during the preparation process. These specific features make the final sample DALC exhibits an ideal specific capacity of 478 F g−1 in a three-electrode system at a current density of 1 A g−1, which is the highest level for all the previously reported biomass-derived carbon materials (without the presence of any metal oxides, which possess excellent specific capacity originally). Besides, the assembled symmetric supercapacitor in a two-electrode system also exhibits a superb specific capacitance of 358 F g−1 at 1 A g−1. All the results indicate that the DALC possesses a great potential for electrode materials of supercapacitors.