A VOLTAMMETRIC STUDY OF THE ELECTRODEPOSITION CHEMISTRY IN THE FE-S SYSTEM

The electrochemical mechanism of iron sulphide deposition on a Pt substrate in organic solution (diethyleneglycol) containing FeCl2 and S8, has been studied by means of cyclic voltammetry, chronopotentiometry and coulometry. The redox processes occurring at different potentials have been investigated to ascertain the potential range at which the iron sulphide deposition occurs. The region between -0.45 and -0.65 V (sce), was identified as the one which assures a suitable composition and good adhesion of the films to the substrate at 120-degrees-C. Films have been characterized by Energy-Dispersive X-ray analysis (EDX). A spreading in the film composition was observed which accounts for the formation of an amorphous phase. The deposition mechanism appears to involve first the reduction of the S8 species to S8(2-), which adsorbs onto the Pt surface while the Fe2+ ions diffuse through the double layer until they precipitate on the adsorbed sulphide species which thus constitute the first nucleation sites of iron sulphide films.