The Effect of Concentration Nanoparticles MnO_2 DOPED in Activated Carbon as Supercapacitor Electrodes

摘要

A symmetric supercapacitor has been fabricated using activated carbon adopted different concentration the nanoparticle manganese dioxide (MnO_2)-activated carbon (AC) composite as the electrode materials. The composite electrodes were prepared by mechanically mixing the activated carbon, MnO_2, and PVDF polymeric solution as a binder. The concentration of MnO_2 was varied from 0% until 20%. The charge storage mechanism in MnO_2 electrode, used in the aqueous electrolyte, was investigated by cyclic voltammetry and the impedance testing was done on two electrodes system. The result clearly showed that the low concentration of nanostructured MnO_2 has improved the specific capacitance of supercapacitor via pseudocapacitive charge storage mechanism and the increased of surface area. However, further increasing the MnO_2 content in the electrode decreased the capacitive performance and deteriorated the specific surface area of the electrode, mainly due to the aggregation of the MnO_2 particles within the composite. Structural analysis of the nanocomposite electrodes was characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. Additionally, the electrochemical properties are evaluated through cyclic voltammetry, electrochemical impedance spectra, and galvanostatic cycling measurements. The results demonstrate this MnO_2/AC composite owes homogeneous particle size of nanometer dimension. The experimental results showed that the highest specific capacitance of 372 F/g at the scanning rate of 10 m/V is achieved with a fairly low MnO_2 nanomaterials loading (5 wt. %) in 3 M KOH. The maximum cycle life of the supercapacitors 4500 cycles. Besides, the impedance tests results show that the charge transfer resistance of this composite is 0.88 Ω.