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Owing to the excellent properties of high selectivity, high thermal stability, and low cost, in the past twenty years, mixed protonic-electronic conducting hydrogen separation membranes have received extensive attention. In particular, dual-phase mixed protonic-electronic conducting membranes with high ambipolar conductivity are more attractive because of the high hydrogen permeability. This paper aimed to present a review of research activities on the dual-phase membranes, in which the components, the characteristics, and the performances of different dual-phase membranes are introduced. The key issues that affect the membrane performance such as the elimination of the inter-phase reaction, the combination mode of the phases, the phase ratio, and the membrane configuration were discussed. The current problems and future trends were simply recommended.

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H 2 permeability of the mixed protonic and electronic conducting membranes can be enhanced by the adjustment of the operating conditions. BaCe 0.8 Y 0.2 O 3−δ (BCY)−Ce 0.8 Y 0.2 O 2−δ (YDC)/BCY−Ni hollow fiber membranes were prepared, and their H 2 permeation fluxes under a gas atmosphere containing water vapor and CO 2 were systematically investigated. The influences of H 2 partial pressure in feed stream, steam, or CO 2 concentration in sweep gas, sweep gas flow rate, and operating temperature on H 2 permeation fluxes were studied. When the sweep side was humidified, the H 2 permeation flux of the membrane was increased and reached 1.21 mL cm −2 min −1 at 900 °C. When using 20% CO 2 −N 2 as the sweep gas, H 2 permeation flux of the membrane was further increased because of the presence of the reverse water−gas shift (RWGS) reaction, achieving 3.03 mL cm −2 min −1 at 900 °C, one of the highest H 2 fluxes ever reported for mixed protonic and electronic conducting membranes. Without adding extra catalyst, the conversion of CO 2 reached 42.5% when using 7% CO 2 −N 2 as the sweep gas at 900 °C, indicating that the membrane material itself has a certain catalytic activity for RWGS. In addition to the excellent H 2 permeability, the membrane also showed good stability in a H 2 −CO 2 -containing atmosphere, highlighting its promising application as the membrane reactor for H 2 separation and CO 2 transformation.