Reference electrode placement and seals in electrochemical oxygen generators

We report measurements and numerical calculations of the potential distribu tion within a thin solid electrolyte near active (current-bearing) electrod es. These studies demonstrate two principles: (1) In a flat-plate geometry, the electrolyte is approximately equipotential beyond a distance of about three electrolyte thicknesses from the edge of the active electrodes. (2) I f one of the active electrodes on one side of the electrolyte extends beyon d the other, it strongly biases the potential of the electrolyte far from t he active region. We show that these effects make it challenging to measure electrode overpotential accurately on thin cells. However, we also show th at these effects can be useful for protecting glass-ceramic seals in an oxy gen generator stack against electrochemical degradation/delamination. (C) 2 000 Elsevier Science B.V. All rights reserved.