Oxigen reduction on chalcosite, pirite and galene in alkaline medium.

The oxygen reduction reaction (ORR) was studied on chalcosite, pyrite and g alene by cyclic voltammetry and stationary potential measurements using a d ouble channel electrode flow cell (DCEFC) at pH = 14. The electrode surface was characterized using thermodynamic and voltammetric data. Stationary vo ltammetry results show that molecular oxygen is reduced to peroxide ions, H O2-, in all cases. At experimental pH, the O-2 reduction occurs on chalcosi te surface containing Cu2S film and on pyrite surface supporting Fe(OH)(3) film. In the case of galene, the formation of elemental S on generator elec trode (due to surface chemical oxidation) and collector electrode of the fl ow cell (due to oxidation of the generated sulphide ions) hinder the electr oreduction of oxygen, impeding the determination of the kinetic parameters, k(1) (direct way) and k(2) (indirect way). From the k(1)/k(2) ratio, chalc osite appears to be the best catalyst for ORR. In fact, this mineral produc es less HO2 ions than galene and the oxidation of flotation collectors is r educed.