Electrochemical behavior of amorphous carbon films: kinetic and impedance spectroscopy studies

Impedance spectra and potentiodynamic curves of oxidation and reduction rea ctions in the quinone/hydroquinone and Ce3+/4+ systems were measured in a 0 .5M H2SO4 solution on amorphous carbon thin-film electrodes grown by magnet ron sputtering or ion source techniques. The electrode equivalent circuit c ontains a constant phase element. Only narrow-bandgap ("graphitelike") amor phous carbon is electrochemically active; however, the wider bandgap ("diam ondlike") material also acquires the activity on "doping" it with platinum (ca 10%) in the course of film growth. The admixture of platinum does not e ffect film conductivity; its action probably is of catalytic character. In its electrochemical activity, the platinum-containing amorphous diamondlike carbon films resemble boron-doped polycrystalline diamond. (C) 1999 Elsevi er Science S.A. All rights reserved.