Rapeseed stalk-derived hierarchical porous carbon as electrode material for supercapacitors

This study explores the potential of renewable post-harvest residue, waste rapeseed (Brassica napus L.) stalk (RS), as a novel precursor for supercapacitor electrodes. Hierarcihal porous carbon with a surface area of 846–1276 m²/g was obtained from RS via subsequent high-temperature carbonization at 900°C and KOH activation between 600 and 900°C. The electrochemical performance of the hierarchical porous carbon was tested in both a three-electrode system and a symmetric supercapacitor with two-electrode. The electrode of carbonized RS activated at 600˚C (RSC-600-K3), which is notable for its high content of quarternary nitrogen (N-Q), unique folded structure and incorporation of heteroatoms, demonstrated superior electrochemical performance in various tests. In the three-electrode system, the optimal active sample RSC-600-K3 electrode exhibited a high areal capacitance of 302.8 mF/cm² at a current density of 0.1 A/g (1.1 mA/cm²), outperforming other samples owing to its effective porous morphology and the presence of N, S heteroatoms. RSC-600-K3 also exhibited a maximum energy density of 42.1 Wh/cm² and a maximum power density of 15.3 kW/cm². Additionally, the RSC-600-K3 electrode maintains a remarkable capacitance retention of 98.9 % after 8000 cycles, indicating excellent long-term cycling stability at a current density of 0.1 A/g. These findings suggest that the RSC-600-K3 electrode holds great promise for high-performance energy storage applications, making it a valuable candidate in the field of energy storage technology.