Electrochemistry of the oxygen electrode in the KNO3KO2 system,a comparative study

Equilibrium and voltammetric measurements have been performed in molten KNO₃ on the oxygensuperoxideperoxide redox system. The results are compared with those previously reported for the eutectic NaK nitrate solvent (MNO₃). In KNO₃, superoxide ions are far more stable and peroxide ions are formed only at very negative potentials, where mainly solvent reduction produces a blocking K₂O₂ deposit on the (Pt) cathode. Other differences between the two solvents, such as in thermal stability and diffusion coefficients of electro-active species are relatively small but the KNO₃KO₂ system is more corrosive against glass and graphite. From rde limiting currents and independently measured or estimated solubility data of oxygen, extremely large diffusion coefficients D(O₂) are found in both solvents. They range from 50 to 100 times the expected values.