Co 2 MnO 4 /Ce 0.8 Tb 0.2 O 2-δ Dual-Phase Membrane Material with High CO 2 Stability and Enhanced Oxygen Transport for Oxycombustion Processes.

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 CO 2 atmospheres, which limits their applicability in oxycombustion processes. On the other hand, some dual-phase membranes are stable in CO 2 and SO 2 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 0.8 Tb 0.2 O 2-δ , CTO) and an electronic-conducting spinel phase (Co 2 MnO 4 , 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 NiFe 2 O 4 (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 CO 2 -rich environments. This dual-phase membrane shows excellent potential as an oxygen transport membrane or oxygen electrode under high CO 2 and oxycombustion operation.