Facile fabrication of self-doped N/O-rich hierarchical porous carbon from wild shrimp carapace with stud-like calcium carbonate arrays for supercapacitors

The waste shells of crustaceans such as shrimp and crab are valuable raw materials for the preparation of heterogeneous element self-doped porous carbon. Herein, a carapace-based in-situ N/O co-doped hierarchical porous carbon (HPC) for supercapacitor electrode material was prepared by a simple CO2 activation method. Benefiting from the extraordinary microstructure and chemical composition of shrimp carapace, the unique “oversized-threaded pore-macropore-mesopore-micropore” HPC exhibited ideal electrochemical performance in a 6 mol/L KOH electrolyte solution, with higher energy density of 10.32 Wh/kg and power density of 5.05 kW/kg, respectively, making it a promising electrode material for supercapacitors. Furthermore, in order to make clear the formation mechanism of threaded hole HPC, the raw materials of the carapace were treated by decalcification and deproteinization, respectively. The results show that the natural stud-like calcium carbonate array with a unique triangular distribution in the shrimp carapace plays an important role as an in-situ template in the formation of hierarchical porous carbon, which offers the as-prepared porous carbon material with unique structure and excellent properties. This strategy provides the effective use of wasted biomass resources for energy storage systems.