Porous carbon derived from sorghum stalk for symmetric supercapacitors

Sorghum stalk based porous carbons (SSCs) have been synthesized through a simple carbonization method at 800 degrees C used sorghum stalk as carbon precursor and ZnCl2 as activating agent. The morphology and structure of the SSCs are investigated by scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, Raman spectra and X-ray diffraction. Undergoes activation at optimal amount of zinc chloride (sorghum stalks to ZnCl2 is 1 : 1), the resulting samples, labeled as SSC1.0 has a porous texture with high specific surface area and efficient ion diffusion channels (1354.7 m(2) g(-1) specific surface areas and 0.765 cm(3) g(-1) pore volumes), and the sample also has superhydrophilicity characterized by water contact angles. As supercapacitor electrode, it can deliver 216.5 F g(-1) specific capacitance at 0.5 A g(-1), 75% capacitance retention even at 8 A g(-1) in 2 mol L-1 KOH aqueous electrolyte and excellent cyclic stability with 92% capacitance retention after 5000 cycles at 5 A g(-1). Moreover, the assembled SSC1.0//SSC1.0 symmetric cell has wide voltage range of 1.8 V, and high energy density in 0.5 mol L-1 Na2SO4 aqueous electrolyte.