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Development of high energetic nano porous electrode by controlled anodization of aluminium

Subir Paul*, Rakib Baidya

PureAl (99.99%) was electropolished in a solution of Perchloric acid and Ethanol and anodized in galvanostatic circuit usingAl cathode in sulphuric acid and oxalic acid solutions at different concentrations and temperatures, in order to formnanoporous alumina template.Anodization process was found to be strongly dependent on potential, type of acid, its concentration and temperature. Single anodization produces poorly ordered structure. The concave texture of theAl surface, which was formed by selective removal of the film after the first anodizing step, is used to induce the ordered formation of pores even at the initial stage of anodization in the second step. Much ordered nano porous template was fabricated. Pore size was found to be strongly dependent on the concentration and type with type of acids, concentration and potential. Anodizing in sulphuric acid produced smaller pore size compared to that in oxalic acid. Scanning electron microscopy revealed pore diameter in the range 30-150 nm in general. Average pore size was estimated from X-ray diffraction pattern, using SchererÂ’s formula and nano pores as below 15 nm was achieved. Polarization study of the electrode was carried out. Both exchange current density and limiting current density were found to influenced by pore size. The smaller the nano pore, higher is the current density.