The AC conductivity of fluorite‐structured La2Ce2O7 ceramic was measured under air and argon with different humidity between 250 and 550 °C. It was observed that the total conductivity in wet air and argon was higher than that under dry atmospheres. The effect of water vapor partial pressure ($ {P_{\rm {H_2{\rm O}}}} $) on the conductivity of La2Ce2O7 in air was investigated in detail. The total conductivity increased remarkably with the water vapor partial pressure, and this phenomenon became more notable at lower temperatures. The enhancement of the conductivity was attributed to the proton conduction behavior of La2Ce2O7 in wet atmospheres, and the proton conductivity reached 6.68 × 10–5 S cm–1 in wet air (3% H2O) at 550 °C. The relationship between the proton conductivity (σH) and $ {P_{\rm {H_2{\rm O}}}} $ in wet air could be fitted to $ \sigma_{\rm H} \propto {P_{\rm {H_2{\rm O}}}^{1/2}} $. The estimated proton transport number increased with increasing water vapor partial pressure and decreasing temperature, and varied between 0.05 and 0.89 in this study.

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In this work, a ceramic oxygen pump based on dysprosium and tungsten co-doped bismuth oxide (DWSB) was synthesized and characterized. The DWSB oxygen ion conducting electrolyte with a composition of Dy 0.08 W 0.04 Bi 0.88 O 2-δ displayed the highest oxygen ion conductivity and was chemically compatible with the La 0.8 Sr 0.2 MnO 3-δ (LSM) electrode material. A composite electrode was fabricated with DWSB-LSM in the mass fraction of 50:50 exhibiting the lowest polarization resistance with the DWSB electrolyte. In the composite electrode, larger DWSB particles act as backbone for the oxygen transport pathway, while LSM particles deposited on the surface of the DWSB backbone serve as mixed ionic-electronic conductors accelerating surface oxygen exchange. An oxygen flux of 5.9 mL cm −2 min −1 at 650 • C under 1 V applied bias was realized in the DWSB electrolyte (0.75 mm) supported membrane incorporating DWSB-LSM electrodes on feed and permeate sides. Further improvements to the electrochemical performance were achieved by fabricating a thin, electrode supported DWSB membrane (∼12 µm). The current density for the electrode-supported cell was 5.4 Acm −2 under 2 V applied bias at 650 • C which corresponds to an oxygen flux of 17 mL cm −2 min −1. Higher bias voltages were observed to accelerate the electrode reaction process leading to reduced polarization resistance that resulted in a remarkable growth of current density. This intelligent DWSB based oxygen pump is a promising materials system for high performance electrochemical oxygen separation.