Green and facile preparation of hierarchical porous carbon with a 3D honeycomb-like structure for high-performance supercapacitors

The urgent need for sustainable energy development is contingent on pollution-free technologies, which has sparked widespread interest in exploring environmentally favorable methods employing inexpensive and abundant starting materials. In this study, 3D honeycomb-like hierarchical porous carbons were prepared using a green molten salt activation method, with renewable biomass waste cotonier catkin (CC) as the carbon source and non-toxic salt KHCO 3 as the activating agent and were used as electrodes for supercapacitors . Specifically, the optimal CC-HPC-1:3 sample has a 3D honeycomb-like structure with a high specific surface area (970.5 m 2  g −1 ) and a relatively applicable pore volume (0.54 cm 3  g −1 ) as well as abundant multi-heteroatoms doping (nitrogen: 3.64 at. %, oxygen: up to 11.22 at. %). As anticipated, the CC-HPC-1:3 electrode exhibits intriguing electrochemical properties in aqueous solution, including an excellent specific capacitance of up to 284.5 F g −1 at 0.5 A g −1 , good rate capacitive behavior (194.2 F g −1 retain at 10 A g −1 ) and low resistance. Notably, the assembled symmetric supercapacitors based on CC-HPC-1:3 carbon materials with a wide voltage window of 1.8 V result in a high energy density of 16.1 Wh kg −1 at 180 W kg −1 and good stability with a capacitance ratio >96 % after 10,000 cycles. Our work presented a very competitive strategy for synthesizing sustainable new green electrode materials for high-performance and low-cost energy storage devices due to the simple and environmentally friendly preparation of CC-HPC.