The breakdown of β-alumina at positive and negative potentials

The breakdown of β^″-alumina at blocking electrodes, over a range of potentials from ?3 V to +8 V relative to the I₂/NaI couple, has been studied. The dependence of current and of interfacial capacitance on potential indicates that oxygen reduction occurs at a less negative potential (ca. ?1.8 V) than sodium deposition (ca. ?2.9 V). No evidence of anodic decomposition could be found over the entire potential range, suggesting that there is a substantial kinetic barrier to formation of oxygen gas from the oxygen anions in the lattice.