Rice husk-derived nitrogen-doped graphitic carbon/graphene nanosheets self-assembly for high-performance supercapacitors with chemical blowing method

Carbon materials derived from waste biomass are increasingly popular in energy devices due to their renewability, environmental benefits, and rich heteroatom functionalization. Herein, a simple and low-cost method for synthesising rice husk-derived nitrogen-doped graphitic carbon/graphene nanosheets (RNGNs) by chemical blowing was developed. Carbon was derived from rice husk (RH), while nitrogen was sourced from ethylenediaminetetraacetic acid and iron sodium salt hydrate (EDTA-FE), serving multiple roles as a blowing agent, an activating agent and a graphitization catalyst in a closed system. This approach facilitates the formation of a unique 3D structure of 2D graphene self-assembly on the wrinkled surface of graphitic carbon. As an electrode material for supercapacitors, the obtained RNGN800-1:1 with high nitrogen content (5.02 %) shows good electrical conductivity and a large specific surface area (1130 m(2) g(-1)). These characteristics bring about an impressive electrochemical performance (334.5 F g(-1) at 0.5 A g(-1), 75.6% retention at 20 A g(-1)). Moreover, when assembled into symmetrical device, the RNGN800-1:1 demonstrates a high power density of 9.4 kW kg(-1 )and an excellent energy density of 15.2 Wh kg(-1) with outstanding long-term cyclability (remains 94.77 % after 25000 cycles). This study introduces a straightforward and environmentally friendly approach for synthesizing nitrogen-doped graphitic carbon/graphene nanosheets from sustainable biomass resources. The resulting material is expected to have broad applications across various areas, including adsorption, catalysis, and energy storage.