Reverse cation segregation and crack self-healing of Ba_0.3Sr_0.7Fe_0.9Mo_0.1O_3-δ perovskite four-channel hollow fiber membrane

The cation segregation in a perovskite-type membrane deleteriously affects the membrane performance and durability. Recovery of segregation is a great challenge because of the complexity of segregation products and severe limitations from the stability of perovskite oxide. This work presents a novel approach for reversing the surface cation segregation by hydrogen-induced annealing which further shows the ability of healing defects and cracks in the oxide bulk. Ba_0.3Sr_0.7Fe_0.9Mo_0.1O_3-δ (BSFM) four-channel hollow fiber membranes were prepared by one-step thermal processing. A low hydrogen concentration (5 vol %) and a mild temperature (900 °C) were used to anneal the as-prepared BSFM hollow fiber membrane and served to trigger outright reverse segregation of massive complex oxide precipitations at grain boundaries and a self-healing of cracks formed during the sintering stage. The reverse segregation significantly alters the composition and structure which directly affects the performance of BSFM membrane, such as mechanical strength, electrical conductivity, oxygen permeability, and stability. A maximum breaking load of 31.6 N is reached for the hydrogen-induced membrane which is approximately 6 times of the as-prepared BSFM membrane. Hydrogen-induced membranes, having high oxygen permeation flux and low activation energy, can operate stably in partial oxidation of methane catalytic membrane reactor for more than 120 h. Our results demonstrate the feasibility of hydrogen-induced reverse segregation and crack self-healing in the perovskite-type dense membrane, suggesting new directions to design the high-performance materials based on perovskite oxides for application in catalysis, electrocatalysis, and separations in the future.