Electrodeposition of nickel, cobalt, and iron on polypyrrole films

Ni, Co, and Fe, which are metals with relatively low redox potentials, have been electrodeposited on a polypyrrole surface. The conductivity of polypyrrole depends on its oxidation state: the reduced state of the polymer film (at negative potentials) is poorly conducting, whereas the partially oxidized state shows high electronic conductivity (at positive potentials). The redox potentials of the deposited metals are located within the potential range of the low-conductivity state of polypyrrole. The metal layer is deposited under two-step potentiostatic conditions. First, the polymer is oxidized. Next, the metal reduction potential is applied. At this potential, the polymer maintains its high conductivity for a short time, allowing metal deposition to occur on the polymer surface. The amount of metal deposited on the polypyrrole depends on the thickness of the polymeric layer and the concentration of metal ions in solution. Nickel and cobalt form dendritic structures, whereas the iron film is more uniform.