Current vs. voltage behavior of Hebb-Wagner ion-blocking cell through compound (Bi1.46Y0.54O3) decomposition and decomposition kinetics

•I vs. U of Hebb–Wagner ion-blocking cell through compound decomposition is quantitatively explained.•Galvanostatic temporal variation of U indicates the decomposition voltage and reoxidation kinetics.•Decomposition mechanism of (Bi1 − xYx)2O3 is elucidated.

The current (I) vs. voltage (U) behavior of an asymmetric ion-blocking cell, Pt,aO2o|Bi1.46Y0.54O3|Pt was examined, at a fixed temperature of 700 °C, over a U range far exceeding the decomposition voltage U⁎ relative to the reference oxygen activity aO2o of the electrolytic compound Bi1.46Y0.54O3. It has been observed that until before decomposition, I vs. U behaves in a usual way, resulting in the partial electronic conductivity of the compound; decomposition starts always at a voltage a little over U⁎, indicating the presence of an energy barrier to decomposition; once decomposition starts at the blocking cathode, I vs. U immediately turns linear with a resistance much higher than the expectation, the total resistance of the electrolytic compound itself, indicating the presence of overwhelming anodic overpotential; decomposition of the compound proceeds as (Bi0.73Y0.27)2O3 → (Bi0.73 ‐ δY0.27)2O3 ‐ 3δ + δ(2Bi + 1.5O2); open-circuit voltage relaxation upon depolarization from - U(> - U⁎) always exhibits a time duration at − U⁎, indicating the reoxidation of reduced Bi. The I vs. U variation over the entire range of U as well as the decomposition kinetics of the compound are quantitatively described.