N and S co-doped 3D hierarchical porous carbon as high-performance electrode material for supercapacitors

The use of renewable and environmentally friendly biomass to prepare carbon materials with a hierarchical porous structure and large specific surface area has attracted great attention in energy storage devices (Supercapacitors, SCs). Here, a succulent-leaf-derived carbon material with a hierarchical porous structure (N-S-HPC) was prepared through a one-step carbonization strategy using Mg(NO3)2·6H2O and ZnCl2 as double activation agents and CH4N2S as S and N source. The N-S-HPC specific capacitance reached 455.3 F g−1 at 1 A g−1, and with 1 M Na2SO4 electrolyte. The assembled N-S-HPC//N-S-HPC symmetric SCs could enhance the voltage window to 1.8 V. Meanwhile, N-S-HPC exhibited the specific energy of 19.89 Wh kg−1 (450 W kg−1) and highly stable cycling performance. Compared with previously reported biomass-derived carbon materials, N-S-HPC has the advantages of i) hierarchical porous sturcture and 2136.2 m2 g−1 maximal specific surface area, allowing accommodation of more ions; ii) 1177.5 m2 g−1 specific surface area for mesopores and macropores, providing shorter diffusion pathways; iii) rich co-doping of N (9.5 at.%) and S (2.21 at. %), increasing pseudocapacitive contribution and improving surface wettability. All these data indictae the great potential application prospect of N-S-HPC, suggesting the importance of biomass-derived carbon materials for symmetric SCs.