Polypyrrole films polymerised on a nickel substrate

A polypyrrole (Ppy) film has been deposited on a Ni electrode by anodic pol ymerisation from acetonitrile solutions. X-ray photoelectron spectroscopy ( XPS) analysis shows nickel Ni2+ chemically bound to the polymer chain. Impe dance spectroscopy has been employed to characterise this new material in a system of metal/film/electrolyte in a Frequency range 10(5)/10(-2) nz. The ac response of the film consists of four or three separable elements depen ding on the film's thickness. Incorporation of nickel ions into electronica lly conducting polymer causes, (i) negligible changes ill a polymer redox r esistance (high frequency response): (ii) considerable decrease of conducti vity responding to ac signal at medium Frequency; (iii) linear dependence b etween resistance measured at medium frequency of ac signal and electrode p otential appeared to be caused by nickel presence in the film. Effective di ffusion coefficient established fur Ppy layers on Ni, Pt and stainless stee l at OCV potentials are 1.2 x 10(-10), 1.0 x 10(-8), and 1.2 x 10(-9) cm(2) s(-1), respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.