MODIFICATION OF GRAPHITE FIBER ELECTRODES BY ELECTROOXIDATION AT HIGHPOTENTIALS

Graphite fibre electrodes were modified by electro-oxidative treatment s at potentials between 1,9 and 2,4 V in sulphuric acido solutions. Th eir behaviour was studied by cyclic voltammetry and electrochemical im pedance spectroscopy, with the aim of clarifying carbon surface oxide formation. The first changes occur on the surface with an increase of surface roughness and electrode activation by a higher concentration o f surface oxides. After long treatment times, electrode passivates by formation of a multilayer oxide which inhibits characteristic electroc hemical processes. impedance measurements show a decrease of capacity, that maybe associated with changes in semiconductor properties oi gra phite.