Highly Regulated Electrodeposition of Needle-Like Manganese Oxide Nanofibers on Carbon Fiber Fabric for Electrochemical Capacitors

The needle-like manganese oxide (α-MnO 2 ) nanofibers were anodically deposited onto the conductive carbon fiber fabric for electrochemical capacitor application. The charge storage mechanism in the manganese oxide nanofiber electrode was investigated using cyclic voltammetry in aqueous and nonaqueous electrolytes containing various alkali metal salts. The results revealed that the protons intercalate into the interior region of the manganese oxide bulk in aqueous electrolytes, whereas the alkali metal cations reach only the near-surface region. The specific capacitance of the manganese oxide nanofibers coated on carbon fabric could reach as high as 432 F g −1, which is much higher than that of manganese oxide nanofibers coated on stainless steel (177 F g −1 ) at a charge/discharge current density of 5 A g −1 in 1 M Na 2 SO 4 aqueous electrolyte. The improved capacitance could be attributed to the combination of spaced manganese oxide nanofibers and the conductive carbon fibers, which facilitates the electron conduction and electrolyte transport through the film electrode.