Measurement of the Proton and Oxide-Ion Conductivities of Dual-Ion Conductors by Switching the Current Direction

H⁺/O^2- dual-ion conductors have demonstrated superior performance in fuel cells and electrolysis cells. However, a simple and precise method for measuring the H⁺ and O^2- conductivities of dual-ion conductors is lacking. This study developed electrochemical impedance spectroscopy (EIS) tests under direct current. Coupled with water electrolysis on one electrode by introducing water vapor, EIS tests can measure the individual conductivities of H⁺ and O^2- simply by switching the current direction. In addition, the H⁺/O^2- dual-ion conductivity is measured when water vapor is applied to both electrodes. The H⁺, O^2- and dual-ion conductivities of the state-of-the-art BaCe_0.7Zr_0.1Y_0.1Yb_0.1O₃-_δ (BZCYYb) are measured and compared with those of other dual-ion conductors for the first time. La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ shows H⁺, O^2- and dual-ion conductivities comparable to those of BZCYYb at temperatures below 625 °C. Therefore, this study has developed a novel method to measure the ionic conductivities of dual-ion conductors simply and precisely.