CO2 corrosion and recovery of perovskite-type BaCo1−x−yFexNbyO3−δ membranes

Corrosion in CO2 and recovery in CO2-free gas of BaCo1−x−yFexNbyO3−δ (x=0.2–0.8, y=0.1–0.5) perovskite membranes were studied at 800–1000 °C for potential application in oxyfuel combustion. The oxygen permeation fluxes decreased during exposure to CO2, which became less pronounced with increasing content of Fe and/or Nb. No significant degradation was observed for the cobalt-free composition with high Fe/Nb contents, BaFe0.55Nb0.45O3−δ. A combined analysis of XRD, IR, TGA, and SEM-EDS revealed that degradation in both the phase composition and microstructure with carbonate formation occurred during annealing in CO2, particularly for samples of low Fe/Nb content. The enhanced CO2 resistance of the perovskite due to Fe/Nb doping was found to accord with an increasing average metal–oxygen bonding. The loss of oxygen permeability caused by CO2 was rapidly recovered by switching the sweep gas back to a CO2-free inert gas. Decomposition of carbonate and formation of Ba(Co, Fe)xOy phases took place during the recovery both on the surface and in the decomposed zone. However, the original perovskite phase and dense grain structure was not regenerated.

► Structure and oxygen permeability of BaCo1−x−yFexNbyO3−δ degraded in CO2.
► The degradation in CO2 mitigated with increasing Fe/Nb contents.
► Loss of oxygen permeability caused by CO2 can be recovered.
► Original structure was not regenerated.
► CO2 resistance is connected with the average metal–oxygen bonding.