An Intermediate-Temperature Oxygen Transport Membrane Based on Rare-Earth Doped Bismuth Oxide Dy0.08W0.04Bi0.88O2-δ

In this work, a ceramic oxygen pump based on dysprosium and tungsten co-doped bismuth oxide (DWSB) was synthesized and characterized. The DWSB oxygen ion conducting electrolyte with a composition of Dy0.08W0.04Bi0.88O2-δ displayed the highest oxygen ion conductivity and was chemically compatible with the La0.8Sr0.2MnO3-δ (LSM) electrode material. A composite electrode was fabricated with DWSB-LSM in the mass fraction of 50:50 exhibiting the lowest polarization resistance with the DWSB electrolyte. In the composite electrode, larger DWSB particles act as backbone for the oxygen transport pathway, while LSM particles deposited on the surface of the DWSB backbone serve as mixed ionic-electronic conductors accelerating surface oxygen exchange. An oxygen flux of 5.9 mL cm−2 min−1 at 650°C under 1 V applied bias was realized in the DWSB electrolyte (0.75 mm) supported membrane incorporating DWSB-LSM electrodes on feed and permeate sides. Further improvements to the electrochemical performance were achieved by fabricating a thin, electrode supported DWSB membrane (∼12 μm). The current density for the electrode-supported cell was 5.4 Acm−2 under 2 V applied bias at 650°C which corresponds to an oxygen flux of 17 mL cm−2 min−1. Higher bias voltages were observed to accelerate the electrode reaction process leading to reduced polarization resistance that resulted in a remarkable growth of current density. This intelligent DWSB based oxygen pump is a promising materials system for high performance electrochemical oxygen separation.