Fast Oxygen Separation Through SO2- and CO2-Stable Dual-Phase Membrane Based on NiFe2O4–Ce0.8Tb0.2O2-δ

Composite membranes with enhanced oxygen permeability and unprecedented stability in oxyfuel -like gas environments are reported. Specifically, 60 vol% NiFe 2 O 4 - 40 vol% Ce 0.8 Tb 0.2 O 2-δ (NFO-CTO) composite has been successfully obtained by one-pot fabrication method showing both spinel and fluorite pure phases. Narrow grain size distribution centered around 1 μm and homogeneous distribution of grains is attained, as well as percolative pathways from side to side of the dual-phase membranes. The composite resisted a stability test in wet SO 2 and CO 2 containing gas at 800 °C for 170 h, which represents a step forward toward its use in oxyfuel power plants. The conductivity of both phases is investigated as a function of temperature and oxygen partial pressure ( pO 2 ). Oxygen separation in this kind of NFO-doped-ceria composite membranes occurs via the separate ambipolar transport through the two distinct percolating networks. Oxygen permeation flux values of 0.17 mL·min –1 ·cm –2 and 0.20 mL·min –1 ·cm –2 are achieved at 1000 °C when argon and pure CO 2 are used as sweep gas, respectively, through a 0.68 mm-thick membrane. Experiments at 900 °C showed that the material is stable and effective in pure CO 2 atmospheres and the oxygen permeation is even improved after 76 h on CO 2 stream.