Promising as high-performance supercapacitor electrode materials porous carbons derived from biological lotus leaf

The lotus leaf, a renewable source of biomass, was successfully explored as a low-cost crude carbon source for preparing high-value lotus leaf porous carbon (LLPC) via carbonization and KOH activation. The synthesis method is simple, inexpensive and easily scalable. Testing and analysis showed that LLPC is a good supercapacitor electrode material with a microporous and macroporous structure, a specific surface area (SSA) of up to 2488 m2 g−1, and a high content of oxygen heteroatoms. In a three-electrode system with 6 M KOH as the electrolyte, LLPC-800-1:3 exhibited a high specific capacitance of 379 F g-1 at 1 A g−1 and good rate performance. At a current density of 20 A g−1, the specific capacitance still reached as high as 298 F g−1. Furthermore, after 5000 charging/discharging cycles, the capacitance retention rate was 90%. When the energy density of the electrode was 9.2 W h kg-1, the power density was 491 W kg−1. The achieved electrochemical performance demonstrates that lotus leaves can function as a new biomass material for the production of high-performance supercapacitors and low-cost energy storage devices.