High-Flux Catalytically Activated Ba0.5Sr0.5Co0.8Fe0.2O3–δ Oxygen Transport Membranes toward Oxyfuel Applications

Oxygen transport membranes (OTMs) are a potential route to reduce the energy penalty associated with O2 production for oxyfuel combustion, although their practical implementation requires sufficiently high oxygen permeation rates under technologically relevant operating conditions. In this work, we demonstrate that the performance of Ba0.5Sr0.5Co0.8Fe0.2O3–δ (BSCF) membranes can be substantially enhanced through membrane design, and also by operating them under conditions that appropriately exploit their transport properties. Supported asymmetric BSCF membranes with 20 and 60 µm dense layers were first compared as a function of temperature, feed-side oxygen partial pressure, and Ar sweep flow, showing that further membrane thinning provides progressively limited gains, as surface and gas-phase transport resistances become increasingly relevant. The 60 µm architecture was used to investigate catalytic surface activation with porous BSCF layers modified with Ag or Pd. The Pd-activated membrane exhibited 98 and 12 mL·min–1·cm–2 at 950 and 650 °C, respectively and under O2/Ar gradient, which are among the highest O2 permeation fluxes reported for supported planar OTMs, and exceeding the frequently cited target of 10 mL·min–1·cm–2 at intermediate temperatures. The improvement caused by surface activation, especially at lower temperatures, and the decrease in the apparent activation energy, is consistent with a permeation regime limited by surface exchange kinetics. Additional sweep-flow experiments confirm the strong dependence of permeation on the permeate boundary conditions. These results demonstrate that BSCF membranes can be carefully designed and operated under appropriate oxygen chemical potential gradients and conditions to fully exploit their exceptional oxygen transport properties, providing a basis for future validation under 3-end operating conditions in oxyfuel configurations.