Co₂MnO₄/Ce_0.8Tb_0.2O_2-δ Dual-Phase Membrane Material with High CO₂ Stability and Enhanced Oxygen Transport for...

Oxygen transport membranes (OTMs) are a promising oxygen production technology with high energy efficiency due to the potential for thermal integration. However, conventional perovskite materials of OTMs are unstable in CO₂ atmospheres, which limits their applicability in oxycombustion processes. On the other hand, some dual-phase membranes are stable in CO₂ and SO₂ without permanent degradation. However, oxygen permeation is still insufficient; therefore, intensive research focuses on boosting oxygen permeation. Here, we present a novel dual-phase membrane composed of an ion-conducting fluorite phase (Ce_0.8Tb_0.2O_2-δ, CTO) and an electronic-conducting spinel phase (Co₂MnO₄, CMO). CMO spinel exhibits high electronic conductivity (60 S·cm^-1 at 800 °C) compared to other spinels used in dual-phase membranes, i.e., 230 times higher than that of NiFe₂O₄ (NFO). This higher conductivity ameliorates gas-solid surface exchange and bulk diffusion mechanisms. By activating the bulk membrane with a CMO/CTO porous catalytic layer, it was possible to achieve an oxygen flux of 0.25 mL·min^-1·cm^-2 for the 40CMO/60CTO (%_vol), 680 μm-thick membrane at 850 °C even under CO₂-rich environments. This dual-phase membrane shows excellent potential as an oxygen transport membrane or oxygen electrode under high CO₂ and oxycombustion operation.