Facile synthesis of N-doped hierarchical porous carbon sheets from biomass for supercapacitors

N-doped hierarchical porous carbon sheet was prepared through calcination of a sodium alginate film precursors containing Zn-2-methylimidazole coordination complex. The film precursors could be obtained at room temperature. The introduction of coordination complex cannot cause the change of sheet morphology, but it can promote the generation of large pore structure. Due to the hierarchical porous structure and N doping, the carbon materials present excellent electrochemical behaviors when used as supercapacitor electrode materials. It exhibited a high specific capacitance of 210.4 F g⁻¹ at 2 A g⁻¹ in a two-electrode system with a capacitance retention of 83.4% over 10,000 cycles.