Gradient solid-electrolyte for use with dissimilar gas electrodes

Abstract

The EMF of a solid-state cell, incorporating a composite solid-electrolyte with gradual variation in composition, and dissimilar gas electrodes, has been studied as a function of temperature and partial pressures at the electrodes. The cell with the configuration: Pt, CO'₂ + O'₂||Na₂CO_3x=0|Na₂(SO₄)x(CO₃)_1-x|_x=1|Na₂SO₄||SO"₃+SO"₂+O"₂, Pt was investigated in the temperature range 973 to 1079 K. The solid-electrolyte surface exposed to SO₃+SO₂+O₂ gas mixture was doped-Na₂SO₄, whereas the CO₂+O₂ gas mixture was in contact with pure Na₂CO₃. The composition of the solid solution between the carbonate and sulfate, with hexagonal structure, was varied gradually between the boundary values. It has been found that the EMF of the cell is close to that calculated from thermodynamic data, assuming unit transport number for Na⁺ ions. The gradient in the concentration of sulfate and carbonate ions in the electrolyte does not give rise to a significant diffusion potential.