Electrocatalysis of oxygen reduction by lanthanum-strontium manganate

The electrocatalysis of the oxygen reduction reaction by lanthanum-strontium manganate La0.5Sr0.5MnO3 (LSM) has been studied by cyclic voltammetry using the rotating ring-disc electrode technique (RRDE) in alkaline medium. From the ring-disc data and other kinetic parameters it was concluded that the oxygen reduction occurs by dissociative chemisorption at low overpotentials. At higher overpotentials, the formation of hydrogen peroxide (HO2− in this case) on the electrocatalyst has been observed. The apparent exchange current density for oxygen reduction on LSM has been found to be 2 × 10−7 A cm−2, while the corresponding Tafel slope is 0.100 V per decade. The possible reaction mechanism for electroreduction of oxygen on this oxide catalyst has been discussed.