Hierarchical porous carbon prepared from biomass through a facile method for supercapacitor applications.

The porous carbon with angstrom-sized pores is important in supercapacitor applications, because of its high pack density and high specific capacitance. In this paper, a facile method is proposed for the preparation of hierarchical porous carbon with high-volume angstrom-sized pores. Onion, as the typical biomass in this research, is used as carbon precursor. First, onion was etched by KOH to obtain a water-soluble lignin-potassium-salt/cellulose composite. This composite was further pyrolyzed under N2 atmosphere to obtain onion derived porous carbon (OPC). The morphology and porous structure of OPC were characterized by scanning electron microscope and N2 adsorption/desorption. The supercapacitive performances of OPC were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge. OPC shows high specific surface area with high-volume angstrom-sized pores in carbon matrix. When used as supercapacitor electrode materials, OPC shows high specific capacitance and good cycling stability. This paper opens a general way to prepare porous carbon from biomasses, which will promote the development of biomass utilization, preparation of porous carbon and supercapacitors.