Preparation And Performance Of U-shaped Hollow-fiber Mixed-conductive Membrane For Hydrogen Permeation

A novel hydrogen permeable membrane based on perovskite-type mixed proton-eletronconductor, has attracted a great deal of interest with hydrogen economy coming. Suchmembrane has great potential applications in membrane separators, fuel cells, hydrogensensors and membrane reactors. In this work, SrCe_0.95Tm_0.05O_3-δ（SCTm） membrane wasprepared successfully and its relevant properties were investigated.Firstly, the SCTm powder was prepared by EDTA/citric acid complexing method. Afterpressing, sintering and polishing, the square disk membrane was obtained. X-ray diffraction（XRD） shows both as-prepared powder and the membrane were perovskite structure in agreewith SrCeO₃standard card （JCPDS82-2427）. The scanning electron microscopy （SEM） andgas-tight test indicates the membrane is dense. The electrical conduction behaviors of SCTmmembrane under different atmospheres at high temperature were measured by E/I test on theelectrochemical workstation. The total conductivity under the H₂-containing gases is higherthan those in O₂-containing and inert atmospheres, which indicates the SCTm membrane isproton conductor. With the increasing of temperature and H₂concentration, the totalconductivitity of SCTm membrane increased.The U-shaped hollow fiber membrane has many advantages such as large membrane areaper unit volume, thin walls for hydrogen permeation, as well as good sealing propertiesconsistent expand and shrink freely at high temperatures. The U-shaped SCTm hollow fibermembrane had been prepared via phase inversion-spinning/hanging-sintering method. Thenthe relationship between sintering temperatures and the microstructures of SCTm hollow fiberwas investigated. XRD result shows that the main phase of SCTm hollow fiber are perovskiteafter sintered at1350-1500℃for3h,. SEM indicates that both the grain sizes on the surfaceand the across-section increased with the sintering temperature increasing. However, theapparent density and shrinkage have not changed significantly with the sintering temperatureincreasing. The U-shaped SCTm hollow fiber membranes sintered at1470℃and1500℃for3h can be used for hydrogen tests, because they were gas-tight resulted from the gas-tighttests.The U-shaped SCTm hollow fiber membrane sintered at1470℃for3h was chosen to investigate itshydrogen permeation performance. The hydrogen permeation flux increasedwith the increasing of the feed gas flow rate and argon flow rate, but it became insensitivewhen the feed gas flow rate and argon flow rate reached at equilibrium values (both were20mL·min^-1) respectively. But the hydrogen permeation flux was insensitive to the feed gas flowrate at975℃. And the hydrogen permeation flux increased with increasing temperatures andH₂partial pressures. However, the hydrogen permeation fluxes under the wet conditions arehigher than those under the dry conditions due to increased proton concentrations for the H+hopping via OH groups. For a H₂partial pressure of80%and a steam concentration of3%at975℃, the hydrogen permeation flux was obtained0.138mL·min^-1·cm^-2.With the increasing temperatures and H₂partial pressures, both the conductivity andhydrogen permeation flux increased, which is consistent with the Wagner theory.