Regulation of microstructure to enhance CO2 permeation in Ce1-xGdxO2-δ-molten carbonate dual-phase membranes

The application of CeO 2 -δ -molten carbonate (MC) dual-phase membranes is limited by low CO 2 permeation at high temperatures due to poor oxygen ionic conductivity. Ce 1- x Gd x O 2 -δ -MC ( x  = 0.00–0.03) dual-phase membranes were designed to investigate the effects of Gd-doping on the ion transport capacity and CO 2 permeability. The introduction of Gd 3+ promotes the conversion of some Ce 4+ to Ce 3+ , initially increasing and then decreasing the Ce 3+ /Ce 4+ ratio. This process increases the oxygen vacancy content, with Ce 0.8 Gd 0.2 O 2- δ showing the highest concentration of oxygen vacancies. At 850 °C, the CO 2 permeation flux of the Ce 0.8 Gd 0.2 O 2- δ -MC membrane is more than twice higher than that of CeO 2- δ -MC, increasing from 0.17 to 0.58 mL min −1 cm −2 . Moreover, the microstructure of the Ce 0.8 Gd 0.2 O 2- δ support is regulated using pore formers of different particle sizes, increasing porosity from 24.3 % to 45.7 %. Consequently, the CO 2 permeation flux of the Ce 0.8 Gd 0.2 O 2- δ -MC dual-phase membrane rises from 0.29 to 0.75 mL min −1 cm −2 at 850 ℃ after optimizing the microstructure of the membrane. Furthermore, the long-term permeation test demonstrates excellent chemical stability of the dual-phase membrane. This study provides feasible modification strategies to enhance CO 2 separation.