Electrochemical synthesis of polypyrrole macro-tubes on aluminum substrate

A novel structure of conductive polymer films was synthesized by electropolymerization on aluminum substrate under potentiostatic condition at a relatively high applied potential. A thick film of polypyrrole was electrodeposited onto aluminum substrate from an aqueous electrolyte solution of NaNO3 with pH 12 by applying a constant potential of 2.0 V versus SCE. This polypyrrole film has a good stability with strong adhesion to the substrate surface. However, the morphological structure of the film is different from those previously observed for conductive polymers. Large tubes (ca. 100–200 μm in diameter) are formed, which are spiraled around the cylindrical substrate electrode. Although, the internal channels of these polypyrrole macro-tubes are very wide, the polypyrrole synthesized is sufficiently dense, guaranteeing excellent mechanical stability for this novel morphological structure. On the other hand, such large walls of the macro-tubes have nano-structures.