The reduction of oxygen at a gold flag electrode fully immersed in (53 + 47) mol % (Li-Na)CO3 was investigated at different temperatures (600 approx. 750°C) using cyclic voltammetry and the semi-integral method. It was found that the electrode reaction mechanism depends critically on the scan rate and temperature. The overall mechanism is complicated by adsorption phenomena. This was identified via semi-integral analysis by the appearance of a peak-shaped semi-integrated voltammetric response. An electron transfer number equal to 2 was determined by the simultaneous use of the voltammetric peak and the maximum value of the semi-integral curve. Both the initial surface excess, Γ*, and the mass-transfer parameter CD 1/2 could be determined from the semi-integration of a single voltammogram.