Puffing-assisted preparation of nitrogen-doped porous biomass carbon for zinc-ion hybrid supercapacitors

Zinc-ion hybrid supercapacitors (ZHSCs) have attracted significant attention because of their high power density, high safety, and environmental friendliness. Biomass carbon is one of the most promising electrode materials for ZHSCs due to its low price and wide range of sources. The pore structure and heteroatom doping have very important effects on the electrochemical performance of carbon materials. In this work, a porous carbon derived from old rice was prepared using the puffing and carbonization method. The puffing process significantly increased the pore structure of rice, which provided abundant active sites for charge accumulation and reduced ion transport distances. The porous carbon prepared under optimal conditions exhibited a specific surface area of 1157.66 m2 g−1, representing a salient increase compared to the unpuffed sample (756.16 m2 g−1). Nitrogen doping further enriched the pore structure of the puffed rice carbon, and its specific surface area reached 1651.85 m2 g−1. Density functional theory calculations also showed that N doping could effectively enhance the adsorption of Zn2+ on carbon materials. The ZHSC based on the optimized nitrogen-doped porous carbon cathode and zinc film anode achieved a specific capacity of 164.0 mAh g−1 at a current density of 0.2 A g−1 in 2 M ZnSO4, while also demonstrating improved cycling stability with 94.3 % capacity retention after 10,000 cycles. Furthermore, the device presented an enhanced energy density of 131.2 Wh kg−1 at the power density of 160.0 W kg−1. © 2024 Elsevier B.V.