Electrochemical studies of molten sodium carbonate

Electrochemical studies of sparged beds of sodium carbonate at 900/sup 0/C employing mixtures of oxygen, carbon dioxide, and water vapor were conducted to determine the identities and relative concentrations of melt species. Analysis of experimental current-potential curves was done by fitting the curves with composite curves that consisted of the algebraic sum of eight computer-generated theoretical waves. The most prominent features of the curves were the 1-electron reversible couple O/sub 2//sup -//O/sub 2//sup 2 -/ superimposed on a 2-electron reversible couple proposed to be CO/sub 4//sup 2 -//CO/sub 3//sup 2 -/, O/sup 2 -/ and, at higher overpotential, a 2-electron irreversible wave proposed to be the reduction of C/sub 2/O/sub 6//sup 2 -/ion. ESR spectra confirmed the presence of superoxide ion in frozen-melt matrix. Under sparged conditions, the thermal decomposition of sodium carbonate appears to produce peroxide ion in addition to oxide ion. A sequence of reactions is proposed to account for the interconversion of melt species.