Effects of hydrogen treatment on the surface microstructure and oxygen permeability of La0.7Sr0.3Ga0.3Fe0.7O3 − δ membrane
Abstract A dense La 0.7 Sr 0.3 Ga 0.3 Fe 0.7 O 3 −  δ membrane tube was treated with hydrogen by exposing its tube side to a H 2 stream and the shell side to the ambient air at 950 °C. A porous layer of thickness ~ 500 μm was formed on the membrane surface (tube side) after 16 h treatment. The oxygen permeation measurement was performed by sweeping the tube side of the membrane with helium to carry away the permeated oxygen. The H 2 -treated membrane exhibited a large increase in oxygen permeation flux (by a factor of 4.5 at 950 °C and 10.5 at 800 °C) and a significant reduction in the apparent activation energy, which is attributed to the increased porosity on the tube-side surface. It is suggested that the H 2 treatment altered the rate-limiting step from the surface oxygen exchange to the transport of oxygen in the bulk of the membrane. The H 2 treatment also led to an enhanced depletion of Ga from the membrane surface, which could affect the applicability of the membrane.