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

Abstract

Impedance spectra and potentiodynamic curves of oxidation and reduction reactions in the quinone/hydroquinone and Ce3+/4+ systems were measured in a 0.5M H2SO4 solution on amorphous carbon thin-film electrodes grown by magnetron sputtering or ion source techniques. The electrode equivalent circuit contains a constant phase element. Only narrow-bandgap (“graphitelike”) amorphous carbon is electrochemically active; however, the wider bandgap (“diamondlike”) material also acquires the activity on “doping” it with platinum (ca 10%) in the course of film growth. The admixture of platinum does not effect 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.