Potentiodynamic deposition of polyaniline on non-platinum metals and characterization

Polyaniline (PANI) was potentiodynamically deposited on stainless steel (SS ), Ni, Ti, Al and Pb electrodes from aqueous solutions of NaClO4, oxalic ac id and H2SO4 of different concentrations. Platinum was also used as a subst rate for the purpose of comparison. Although, the non-platinum metals showe d reactivity in the electrolytes, the adsorption of aniline monomer occurre d leading to initiation and growth of PANI during repeated potential sweeps . The nature of voltammograms of the non-platinum metals during PANI deposi tion differed from that of the Pt electrode. Subsequent to potentiodynamic deposition, the electrodes were studied for their electrochemical activity in 0.5 M H2SO4 without and with dissolved redox species. On all metals, the PANI exhibited the potentiodynamic peak at about 0.2 V corresponding to tr ansition from leucoemaraldine (LE) state to emeraldine (EM) state at low sc an rates. However, this peak disappeared on repetition of potential scan an d also at high scan rates. The PANI deposited on non-platinum metals showed response to dissolved redox species. viz, hydroquinone/quinone, ferrous/fe rric, ferrocyanide/ferricyanide, as reflected in the potentiodynamic and ac impedance measurements. However, the peak potential separation of cyclic v oltammograms was very large. (C) 2001 Elsevier Science B.V. All rights rese rved.