STABILITY AND CHARACTERIZATION OF OXYGEN SPECIES IN ALKALI MOLTEN-CARBONATE - A THERMODYNAMIC AND ELECTROCHEMICAL APPROACH

The stability and electrochemical behavior of reduced oxygen species w ere investigated in several alkali molten carbonates at different oxoa cidity levels and temperatures. Theoretical predictions and experiment al results were in good agreement and show that, in Na-K, Li-Na, Li-K, and Li-Na-K melts, peroxide species can only be stabilized in basic m edia. Superoxide species, unstable in lithium-containing carbonate, ca n be stabilized in Na-K under slightly basic conditions. Peroxide/oxid e and superoxide/oxide redox systems were characterized by voltammetri c and convolution potential sweep techniques. It was shown that CO2 do es not participate in the rate-determining reduction mechanisms of bot h superoxide and peroxide species. Electrochemical parameters relative to the cited systems (D, delta, E-degrees, E1/2), as well as the solu bility of reduced oxygen species were determined.