TEST OF A DUAL ELECTRODE GALVANIC CELL IN BINARY CARBONATE MELT

Basicity of the (Li-0.62, K-0.38)(2)CO3, the current choice of electro lyte composition for molten carbonate fuel cells (MCFC's), is defined as -log (aM(2)O), where M represents an alkali metal and aM(2)O is the net oxide ion activity. Net oxide ion activity is defined as the sum of the alkali oxides activities dissolved in the melt. To con-elate me asured cell e.m.f. values with basicity change in the (Li-0.62, K-0.38 )(2)CO3 melt, a dual electrode galvanic cell of the following arrangem ent was tested at 650 degrees C with PCO2 varying above the melt: Au, A-B, CO2, O-2 \ mullite \ A-B, CO2, O-2 \ ZrO2 . Y2O3 \ O-2, Au where A-B represents (Li0.62K0.38)(2)CO3. The response of the cell to PCO2 a t constant PO2 can be explained by thermodynamic model, which states t hat ion transference in the mullite tube is limited to Li+ and/or K+ a nd the dual electrode galvanic cell voltage is a direct measure of Del ta aLi(2)O or Delta aK(2)O for pure (Li0.62K0.38)(2)CO3 melt at consta nt PO2.