Studies on electrochemical deposition of metallic films on conducting polymer

Abstract

Electrochemical polymerization of aniline occur on Pt, Ni and Stainless steel at O.6V, I.05V and O.85V respectively. Oxidative dissolution of Cu and Co at-O.15V and ---{).2Vbefore polymerization of aniline occur on them. Good PANI film is formed on Pt and stainless steel but it does not adhere strongly on Ni surface. Electrodepostion of Cu, Ni and Co occurs on PANI film at -0.33V,-1.30V and -1.IOV vs. SCE respectively. In the SEM study PANI deposits on stainless steel as continuos film. Some craters are found in PANI film. At high magnification, PANI film appears porous with size of micrometer range or so. The SEM analysis confIrmSthe deposition of Cll, Ni and Co on PANI film. Visual examination also reveals brick-red Cu over whole PANI-film. Cu is deposited both in craters as well as in the surface of PANI film. Both at low and high magnification, the morphology of Cu deposition is dendritic cluster which looks dense forest like structure. Ni deposits discreetly some places as a cluster of hemispherical nucleus forms island. Co deposits in some craters of PANI. At high magnification a few isolated hemispherical bright Co nuclei are visible. From the IR spectral analysis of PANI and PANI-Metal samples, it is revealed that there has not been any remarkable change of PANI structure as a result of metal deposition. During the metal deposition PANI is reduced. The reduced PANt-Metal sample shows a peak at -1250cm-1. This peak is not found in PANt which is consistent with secondary aromatic amine converted by the reduction from imine or oxidized imine oramme In the UV-Vis. spectra, PANI shows lower band gap than PANI-Metals. The band gap obtained for PANI, PANI-Cu, PANI-Ni, PANI-Co are 3.76eV, 3.86eV, 3.80eV, 3.83eV respectively. Therefor their conductivity order may be expected to be as: PANI > PANI-Ni > PANI-Co> PANI-Cu. lt may be anticipated that polaron and bi-polaron sites in the PANI do not exist due to reduction during metal deposition. Therefore, decrease the conductivity in PANI-Metal samples. PANI behaves like metal rather than semiconductor. The measured conductivity order is found as: PANI > PANI-Cu > PANI-Ni. The dendritic continuation of Cu deposition on all over PANI film may contribute the increase of conductivity than PANI-Ni where Ni is deposited discreetly some places on PANI film. The X-ray diffraction pattern of PANI sample shows a diffused peak at 29value of 12.2°-12.5°.AIIPANI Metal samples(e.g., PANI-Cu, PANI-Ni, PANI-Co) show same peak at that range which conclude that the order of array of polymer chain i.e., the crystaIlianity of polymer matrix is much poor to amorphous. Thus, it could not be anticipated the crystaIlianity of PANI-Cu, PANI-Ni and PANI-Co samples