A Method to Measure the Proton Conductivity of LiNaSO4 under Fuel Cell Conditions

A method has been developed for measurement of proton conductivity of hydrogen-reducible ionic conductors under protonic fuel cell conditions in which the reducible electrolyte is sandwiched between layers of a nonreducible proton-conducting electrolyte in a disk. The proton conductivity of LiNaSO 4 under the fuel-cell condition was determined with Y-doped BaCeO 3 (BCY) as the nonreducible sandwich layers, using conventional methods under hydrogen at high temperature, under which conditions LiNaSO 4 would otherwise be chemically unstable. LiNaSO 4 and BCY had good chemical and mechanical compatibility in the sandwich disk. The major portion of the ionic conductivity of LiNaSO 4 at 600-680°C is due to Li + and Na + ion transport, and proton conductivity (7.01 X 10 -3 S cm -1 at 600°C to 1.23 X 10 -2 S cm -1 at 680°C) accounts for only 5-10% of total ion conductivity (1.25 X 10 -1 S cm -1 at 600°C to 1.35 X 10 -1 S cm -1 at 680°C). These data explain the poor performance of hydrocarbon conversion fuel cells using LiNaSO 4 as the electrolyte.