Electrocatalytic oxygen reduction with thiospinels and other sulphides of transition metals

Thiospinels and other sulphides were examined systematically with regard to their electrocatalytic activity for oxygen reduction in acid electrolyte. The measurements were carried out by potentiodynamic and galvanostatic methods. The metals cobalt, iron and nickel show the highest activity in sulphur compounds, the best results being obtained by cobalt. Other transition metals reduce the activity. A considerable decrease in activity is observed when sulphur is partly or totally replaced by oxygen, selenium or tellurium; the same effect is observed with disulphides. A simple interpretation of the results obtained is possible considering the geometric and electrostatic conditions in the spinels.