The electrocatalysis of the oxygen reduction reaction by lanthanum calcium manganate, (La0.5Ca0.5MnO3) (LCM) 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 has been assumed that the oxygen reduction occurs by dissociative chemisorption at low overpotentials. At higher overpotentials, the formation of hydrogen peroxide (HO2- in this case) has been observed on this electrocatalyst. The apparent exchange current density value for oxygen reduction on LCM has been found to be 5 <FONT FACE=Symbol>´</FONT> 10-8 A cm-2, while the corresponding Tafel slope is 0.115 V per decade. The possible reaction mechanism for electroreduction of oxygen on this oxide catalyst has been discussed.
fuel cell; metal-air battery; lanthanum calcium manganate; oxygen reduction; HO2- disproportionation
