Nitrogen and Sulfur Co-doped Hierarchical Porous Biochar Derived from the Pyrolysis of Mantis Shrimp Shell for Supercapacitor Electrodes

The preparation of high-value biochar as a supercapacitor is a promising way for biomass utilization. In this work, a self-activation method was proposed to prepare nitrogen and sulfur co-doping hierarchical porous biochar by using mantis shrimp shell as carbon, nitrogen, and sulfur precursors. The porosity and surface chemical properties of biochar were adjusted upon different temperatures. It was found that the obtained biochar had a dendritic and uniform morphology, in which micro-, meso-, and macropores were interconnected regularly in the structure, and the nitrogen and sulfur heteroatoms were successfully homogeneously introduced into the carbon frameworks. On the basis of electrochemical tests, novel shell biochar with an activation temperature of 750 °C demonstrated the highest specific capacitance, which was 201 F g–1 at a current density of 1 A g–1 in a 6 M KOH electrolyte, due to the large BET surface area of 401 m2 g–1, and high nitrogen (8.2 wt %) and sulfur content (1.16 wt %). The in situ template approach from natural biomass provided tremendous potential for the active electrode materials of supercapacitors.