Orr study on fe- and co- doped manganese dioxide with ramsdellite structure

Abstract

Oxygen reduction reaction (ORR) belongs to intensively studied electrocatalytic processes from the point of view of its fundamental and practical significance. Recent developments in Li-air battery (LAB) and fuel cell technologies area demand a new insight into air electrode construction and characteristics including bifunctionality of oxygen electrocatalyst for ORR and OOR (oxygen oxidation reaction). Manganese dioxide has long application as an air electrode and is supposed to be promising as an active layer of the air electrode in LAB. The electrolytic doping procedure can be successfully applied to induce phase composition changes and to incorporate active sites of defect redox pairs Mn+1/Mn+ of various nature in the oxide matrix. Manganese dioxide doped by Fe(II) and Co(II) electrolytically is studied as an air electrode in alkaline electrolyte. Both oxides belong to so-called γ-MnO2 with ramsdellite structure. ORR was studied by the CVA method comparing with NH4+-doped MnO2 with hollandite structure. It can be concluded that electrolytic doping influences the mechanism of ORR (OOR) process. The nature of this influence is discussed. It can be pointed out that Fe(II) and Co(II) additives studied are promising instruments of manganese dioxide bifunctionality in ORR (OOR). The Tafel slope observed on doped MnO2 electrodes for ORR is in agreement with platinum electrode reference data of 60 and 120 mV/dec.