Fabrication of polypyrrole nanorod arrays for supercapacitor: effect of length of nanorods on capacitance.

Arrays of polypyrrole nanorods were fabricated using an anodized aluminum oxide (AAO) template for use as supercapacitors. Gold was deposited on one side of the AAO template by thermoevaporation for use as an electrode and pyrrole was electrochemically polymerized, causing it to grow from the gold electrode into the AAO template. The length of the PPy nanorods was controlled by adjusting the applied charge, and nanorods with three different lengths were prepared: 1.2 microm for 0.5 C x cm(-2), 2.4 microm for 1.0 C x cm(-2), and 4.6 microm for 2.0 C x cm(-2). After the removal of the AAO template in alkali solution, a well-arranged polypyrrole (PPy) nanorod electrode structure having an extremely large surface area was produced. The morphology of the PPy nanorods was monitored by SEM. The capacitive performances of the PPy nanorod array electrodes were investigated by cyclic voltammetry (CV) as well as the galvanostatic charge/discharge test. Greatly enhanced capacity performance was observed in the nanorod electrodes. Also, a higher specific capacitance was observed in the longer nanorod electrode having a larger surface area.