Comparison of the reaction mechanisms of electrocatalytic oxygen reduction using transition metal thiospinels and chelates

Abstract The cathode process of oxygen reduction on thiospinels and other sulphides was examined by potentiodynamic, galvanostatic and rotating ring-disc electrode measurements. The highest activity was found with the sulphur compounds of cobalt and iron. The results are compared with those obtained with iron and cobalt melt chelates of the macrocyclic N 4 type (phthalocyanines, dibenzotetraazaannulenes) because knowledge is required about the reaction itself and the mechanism of the reduction of activity of the non-precious metal catalysts. The reaction scheme for the oxygen reduction is discussed and values of the rate constants of the electrochemical reactions are given.