Na+ transport across the beta alumina-propylene carbonate interface

Interfacial Na⁺ ion transport between polycrystalline beta alumina and propylene carbonate has been studied using a galvanostatic transient technique which separates interfacial overpotential from bulk resistivity effects. No interfacial polarization is detected during ion entry into beta alumina and exit from beta alumina across a dry interface from 30–1000 μA cm^?2. Transport across an interface contaminated with adsorbed water follows Tafel-type i/E behavior with a transition coefficient (α) of 0.24 and exchange current (i₀) of 3.0×10^?6 A cm^?2 at 23°C. Interfacial transport appears to take place through an intermediate state in which the mobile ion is adsorbed on the interface. Large increases in interfacial polarization occur at both dry and hydrated interfaces for ionic currents exceeding the rate of adsorption or desorption.