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New Progress in Research on Oxygen-permeable Membrane for Low Temperature Stable Mixed Conductors of Dalian Institute of Chemical Industry
Recently, the research team led by Yang Weishen and Zhu Xuefeng, researchers of the Inorganic Membrane and Catalysis New Materials Research Group (504 Group) of the State Key Laboratory of Catalysis of the Chinese Academy of Sciences, has made new progress in the study of low temperature stable mixed conductor oxygen permeation membranes. The results were published online in the journal Nano Letters (DOI:10.1021/acs.nanolett.5b03668).
The mixed conductor oxygen-permeable membrane has unique advantages in oxygen separation and membrane catalytic oxidation, attracting widespread attention from academia and industry. However, the operating temperature of the oxygen permeable membrane is generally high (>800°C), resulting in high cost of the membrane module and difficulty in sealing. Therefore, reducing the operating temperature to a low temperature range (350-650 °C) is a goal pursued by scientists in this field. However, numerous studies have shown that oxygen permeation flux of mixed conductor oxygen permeable membranes rapidly decays with time in low temperature regions. In previous studies, the research team has elucidated the mechanism of low-temperature attenuation of phase-stable membrane materials and proposed a wide range of effective solutions (Angew. Chem. Int. Ed. 2013, 52, 3232; J. Membr. Sci. 2015 , 492, 173.). However, the above methods are not suitable for film materials that undergo phase transition at low temperatures, such as Ba0.5Sr0.5Co0.8Fe0.2O3−δ(BSCF) oxygen-permeable membrane materials (AIChE J. 2015, 61, 3879.).
In view of the above problems, the research team conducted in-depth studies on the microstructure changes of the oxygen-permeable membrane BSCF under operating conditions. It was found that the main cause of oxygen permeation flux attenuation in the oxygen-permeable membrane was the phase change at the grain boundary of the oxygen-permeable membrane. For this reason, it has been proposed to introduce nano-particles into the grain boundary of the oxygen-permeable membrane material to prevent the occurrence of phase transformation, thereby suppressing the attenuation of oxygen permeation flux. When nano-particles are introduced at the grain boundary, the nano-particles can pin grain boundaries and limit the diffusion of metal ions along the grain boundary, acting as a "roadblock" to suppress the formation of heterogeneous nucleation and new phases. The research team further demonstrated the effectiveness of the method in terms of both thermodynamics and dynamics. The oxygen-permeable flux of BSCF-modified oxygen membranes modified with nanoparticles is 10-1000 times that of other membrane materials at 550-650°C; more importantly, it is operated at 600°C for 500 h with oxygen permeation flux. No significant attenuation. This new method of introducing nanoparticles into the grain boundary of the material inhibits the phase transition and can be extended to other grain boundary-induced heterogeneous nucleation phase transition systems.
The study was funded by the National Natural Science Foundation and the Frontier Science Breakthrough Project of the Chinese Academy of Sciences.
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