Nickel foam-based manganese dioxide–carbon nanotube composite electrodes for electrochemical supercapacitors

Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 2–4 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of slurries of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNTs) into porous nickel foam current collectors. In the composite electrodes, MWCNT formed a secondary conductivity network within the nickel foam cells. Obtained composite electrodes, containing 0–20 wt.% MWCNT with total mass loading of 40 mg cm−2, showed a capacitive behavior in the 0.1–0.5 M Na2SO4 solutions. The highest specific capacitance (SC) of 155 F g−1 was obtained at a scan rate of 2 mV s−1 in the 0.5 M Na2SO4 solutions. The SC increased with increasing MWCNT content in the composite materials and increasing Na2SO4 concentration in the solutions and decreased with increasing scan rate.