Tuning the two phases ratio by nonmetal ion doping in dual-phase mixed-conductive ceramic membranes

The mixed protonic-electronic conductor of BaCe0.5Fe0.5O3-delta can be automatically decomposed into a dual-phase material of the cerium-rich oxide BaCe0.85Fe0.15O3-delta (BCFe8515) and the iron-rich oxide BaCe0.15Fe0.85O3-delta (BCFe1585). The BaCe0.5Fe0.5O3-delta membrane possessed an extremely high hydrogen (H2) permeation flux, but poor stability. Therefore, in this work, for the first time, the nonmetal P is doped to increase the proportion of the BaCe0.85Fe0.15O3-delta (P-doped Ce-rich) phase to improve the stability of the dual-phase membrane. The developed dual-phasic ceramic membranes of BaCe0.5Fe0.5-xPxO3-delta (BCFePx) (x = 0, 0.025, 0.05, 0.1) exhibit enhanced stability compared to their parent oxides. Under the condition of 950 degrees C, feed gas with dry 50% H2-50% He and sweep gas with wet Ar, the H2 permeation flux of BCFeP0.05 membrane stabilized at 1.56 mL min-1 cm-2 after the long-term stability test for 480 h. The enhanced stability resulted from the increase of the P-doped Ce-rich phase content and the inhibition of Fe2O3 phase precipitation from the BaCe0.15Fe0.85O3-delta (P-doped Fe-rich) phase in the reducing atmosphere by doping non-metal P element. image