Oxygen Permeation and Stability of Ce0.8Gd0.2O2−δ–PrBaCo2−xFexO5+δ Dual–phase Composite Membranes

Abstract

Dual-phase membranes of 60 wt% Ce0.8Gd0.2O2−δ–40 wt% PrBaCo2–xFexO3−δ (0 ≤ x ≤ 2) were prepared by a combined citrate and ethylene diamine tetraacetic acid (EDTA) complexing method. X-ray diffraction (XRD) results revealed the good chemical compatibility between ion-conducting phase CGO and electron-conducting phases PBC2−xFxO after sintering in air. The Fe ionic dopant had a significant effect on the phase structure stability and oxygen permeability under CO2 atmosphere, which was confirmed by XRD, thermogravimetry–differential scanning calorimetry (TG–DSC), scanning electron microscopy (SEM) and oxygen permeation experiments. CGO–PBC0.5F1.5O dual-phase membrane demonstrated a stable oxygen permeation flux of 2.71 × 10−7 mol cm−2 s−1 with 50 mol% He/CO2 as the sweep gas at 925 °C, and this value was much higher than that of perovskite-type membranes. The rate-limiting step in the oxygen permeation process changed from the bulk diffusion to the surface oxygen exchange when the CGO–PBC0.5F1.5O membrane thickness decreased to 0.8 mm or less. Due to the high oxygen permeation fluxes and the excellent structural stability under CO2 atmosphere, the CGO–PBC0.5F1.5O membrane is a great potential candidate material for separating oxygen from air in the oxy-fuel combustion techniques.