Elucidation of subtle degradation mechanisms in composite CO2 separation membranes


Composite membranes for CO2 separation based on CGO (Gd-doped ceria) and the eutectic mixture of Na and Li carbonates, with distinct salt content (around 20 and 40 vol%) and microstructures (starting oxide grain size in the 170-220 nm range), were prepared and tested up to 250 h, at 650 degrees C, under distinct atmospheres (CO2 gradient or fully immersed in CO2 or Ar), to elucidate degradation mechanisms. Substantial oxide grain growth (50-65%) was observed during endurance tests of membranes with higher and lower oxide content, respectively. These relative changes were unable to explain the observed stability, higher for membranes with lower salt content. Combined microstructural, structural and electrochemical analyses of samples revealed that the solu-bility of metal oxides in the molten phase plays a crucial role. While ceria is poorly soluble, Gd oxide dissolves easily under acidic conditions (high CO2, membrane feed side) but precipitates under low CO2 (sweep side). Grain growth with formation of regions with distinct Gd content (core-shell CGO grains) explain the degradation of the oxide scaffold. This information provides important guidelines on membrane design, pointing towards oxide scaffolds with large and well percolated grains, also moderate acidity of the molten phase, to improve membrane stability.



subject category

Engineering; Polymer Science


Jamale, A; Starykevich, M; Marques, FMB

our authors


Work supported by project CICECO-Aveiro Institute of Materials (FCT Ref. UID/CTM/50011/2019) , financed by national (Portugal) funds through the FCT/MCTES, and when applicable co -financed by FEDER under the COMPETE 2020 Program. Specific support (AJ) pro- vided by national funds (OE) , through FCT, IP, in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree -Law 57/2016, of August 29, changed by Law 57/2017, of July 19. MS acknowledges the support of the FCT-2020.00625.CEE- CIND grant.

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