Oxygen exchange-limited transport and surface activation of Ba0.5Sr0.5Co0.8Fe0.2O3−δ capillary membranes

• Published in: Journal of membrane science 2011-02, Vol.368 (1-2), p.223-232
• Main Authors: Kovalevsky, A., Buysse, C., Snijkers, F., Buekenhoudt, A., Luyten, J., Kretzschmar, J., Lenaerts, S.
• Format: Article
• Language: English
• Subjects: activation energy; artificial membranes; BSCF; Capillary; Chemistry; Colloidal state and disperse state; energy-dispersive X-ray analysis; Exact sciences and technology; General and physical chemistry; Membranes; oxides; oxygen; Oxygen exchange; Oxygen permeation; praseodymium; spinning; Surface activation; temperature; X-ray diffraction
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2010.11.034

▶ Oxygen transport through BSCF capillary is significantly limited by surface exchange. ▶ Activation with praseodymium oxide (PrOx) results in an increase in permeation. ▶ Activation leads to a change of limiting step for the oxygen transport. ▶ (Pr,Ba,Sr)(Co,Fe)O3−δ perovskites may be responsible for increase in permeation. ▶ BSCF capillary membranes demonstrate stable performance with time. Analysis of oxygen permeation fluxes through Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) capillary membranes, fabricated via a phase-inversion spinning technique using polysulfone as binder, showed a significant limiting role of the surface-oxygen exchange kinetics. Within the studied temperature and oxygen partial pressure ranges, the activation of core and shell sides of the BSCF capillary with praseodymium oxide (PrOx) resulted in an increase in permeation rate of about 300%. At 1123–1223K the activated BSCF membranes demonstrate almost 3-times lower activation energies for the overall oxygen transport (∼35kJ/mol) than the non-activated capillaries, indicating that the mechanism of oxygen transport through the activated capillaries becomes significantly controlled by bulk diffusion limitations, allowing further improvement of the overall performance by decreasing the wall thickness. XRD, EDS and EPMA studies revealed the formation of (Pr,Ba,Sr)(Co,Fe)O3−δ perovskite-type oxides on the surface of the PrOx-modified membranes, which may be responsible for the drastic increase in oxygen exchange rate. At T>1123K both non-activated and activated Ba0.5Sr0.5Co0.8Fe0.2O3−δ membranes demonstrate stable performance with time, while at 1073K only a small initial decrease in permeation was observed.