H2O-enhanced CO2 transport through a proton conducting ceramic- molten carbonate dual-phase membrane

Abstract

High-temperature membranes for CO2 transport and separation has attracted significant interest from academia and industries due to their potential to mitigate the emissions of CO2 and ultimately global warming/climate change. In this study, we report a dual-phase CO2 membrane fabricated from a porous proton conducting BaZr0.8Y0.2O3-δ (BZY) matrix and eutectic mixture of Li2CO3–Na2CO3 (denoted as MC). The membrane exhibits a high CO2 permeation flux density in the range of 550–750 °C in both dry and wet conditions. Through microstructural optimization, a CO2 flux density as high as 0.34 mL ⋅ cm−2⋅ min−1 at 650 °C and 0.53 mL ⋅ cm−2⋅ min−1 at 750 °C have been achieved with an 0.8 mm thick BZY-MC membrane containing 52% porosity and 50%CO2–N2 feed gas. The high flux is attributed to synergistic effects of microstructure, MC loading and high bulk conductivity of BZY. In addition, we also demonstrate the positive effect of H2O in the permeate side on CO2 flux density and proposed a reasonable mechanism to explain the H2O-enhanced CO2 flux density. With 3% H2O-added into the sweeping gas, the membrane exhibits 30% CO2 flux density enhancement and good stability over 250 h at 650 °C.