Tape-casting and freeze-drying gadolinia-doped ceria composite membranes for carbon dioxide permeation

Porous ceria: 20 mol% gadolinia (20GDC) ceramic membranes were prepared by tape casting (TC) and freezedrying (FD) techniques, obtaining ceramic matrices with randomly dispersed round pores and with an aligned pore structure, respectively. Samples were sintered at 1450 degrees C, followed by infiltration of molten eutectic sodium-lithium carbonates (NLC). The pore morphology of 20GDC-TC and 20GDC-FD composite membranes was evaluated by analysis of scanning electron microscopy images. The electrical resistivity was determined by electrochemical impedance spectroscopy in the 1 Hz - 10 MHz frequency range from 300 degrees C to 700 degrees C, covering the solid-to-molten NLC temperature range, showing that the aligned pore structure improved the conductivity of the ceramic matrix in addition to facilitating molten carbonate infiltration, improving the total (bulk + interfaces) electrical conductivity of the composite membrane. Permeation experiments showed high CO2 permeation rates reached 5.35 x 10- 7 mol m- 2 s- 1 Pa-1 at 800 degrees C. The infiltration of molten sodium-lithium carbonate in gadolinium-doped ceria prepared by the freeze-drying technique is proposed as an optimized procedure for producing membranes for carbon dioxide separation.

Automated summary

The aligned pore structure improved the conductivity of the ceramic matrix and facilitated the infiltration of molten carbonate, enhancing the overall electrical conductivity of the composite membrane. The optimized procedure for producing membranes for carbon dioxide separation is proposed to be the infiltration of molten sodium-lithium carbonate in gadolinium-doped ceria prepared by the freeze-drying technique.