摘要
Porous carbons were obtained from rice husk using two different chemical activation methods and they were investigated as supercapacitors.Their properties were studied using X-ray photoelectron spectroscopy,thermal analysis,potentiometric titration,and nitrogen adsorption isotherm.The specific capacitance measured in both H_(2) SO_(4) and KOH electrolytes in two-electrode cell was up to-150 F/g.The activation method used affected the resulting carbons’features.As expected,the dependence of the capacitance on porosity was found.The ash content reached 36 wt.%and that inorganic mater blocked some pores and limited their accessibility to electrolyte ions and increased the charge transfer resistance.Nevertheless,the main ash constituents such as CaCO_(3),MgCO_(3),Ca_(3)(PO_(4))2(or P_(2)O_(5)),and Fe-and Zn-containing species did not affect the specific capacitance to a large extent.Especially SiO2,even in a relatively large amount(~20 wt.%)T did not play a detrimental role in the capacitance behavior.The results showed that in spite of a high ash content,carbon can exhibit a good capacitive performance provided that it has a favorable porosity and is rich in sp_(2) configurations.
