Structural and Morphological Properties of MnO2/MWCNT Composite Grown Using the Hydrothermal Method for Supercapacitor Application

Manganese dioxide and multi-walled carbon nanotubes (MWCNT) have received considerable recent interest for their potential application in supercapacitors, MnO2 as a pseudocapacitor material and MWCNT as an electrochemical double layer capacitance (EDLC) material. The combination of MnO2 and MWCNT is expected to make promising supercapacitor electrodes. In this study, MnO2 was mixed with MWCNT during the hydrothermal process. The difficulty in obtaining MnO2/MWCNT composite homogeneity in the hydrothermal process provides a challenge to scaling up production. KMnO4 and MWCNT were mixed with 20 mL distilled water and stirred using a magnetic stirrer for 2 minutes, then placed into an autoclave. Heating of autoclave was carried out at 160 degrees C for 3 hours in an oven and followed by cooling at room temperature naturally. Manganese dioxide/MWCNT composites were made in 1:1 and 3:1 ratios. The diffraction peaks of composites indicated that incorporation of MWCNT into MnO2 has provided a crystalline orientation derived from MnO2 and MWCNT. Scanning electron microscopy and TEM imaging demonstrated that MnO2/MWCNT 3:1 composite attained better homogeneity than MnO2/MWCNT 1:1 as indicated by the attachment of MnO2 to the entire nanotubes surface of MWCNT. Increasing of conductivity values have been supported by MWCNT marked decreasing in the R-ct value in electrochemical impedence spectroscopy measurements. Based on cyclic voltammogram measurements, the MnO2/MWCNT electrode 3:1 produced specific capacitation (C-s) of 252 F/g with stability up to 1000 cycles.