Effect of Sulfur Impregnation Temperature on Properties of N-Doped Activated Carbon for Supercapacitor Applications

Sulfur-and nitrogen-co-doped activated carbons were obtained from sulfur modified nitrogen-doped activated carbons prepared from waste medium density fiberboard (MDF) prepared by KOH at 850 C for 60 minutes at a weight ratio of 3:1. And the sulfur was adsorbed by nitrogen-doped activated carbon with different temperatures at 300°C, 400°C, 500°C, 600°C (AC300, AC400, AC500, AC600). The structural properties and chemical surface composition of the activated carbons were evaluated by Elemental analysis, Scanning electrical microscopy, Raman spectra, X-ray diffraction and Adsorption of nitrogen. The results showed that the content of sulfur ranging from 0.03 wt. %~1.64 wt. % in which the content of sulfur in AC400 (1.64 wt. %) is highest comparing with other activated carbons. The BET specific surface area is varying from 1805 m2g-1 to 2081 m2g-1. The activated carbons as the electrode material which was impregnated with 7 M KOH electrolytes were characterized and tested by galvanostatic charge-discharge curves, cyclic voltammetry and alternating current impedance. The specific capacitance was improved from 225 to 264 F/g and AC400 exhibited the best electrochemical behavior with a supreme specific capacitance (264 F/g) and rectangular cyclic voltammetry curves.