Chemical Stability And Hydrogen Permeation Of In-doped SrCe_0.95Tm_0.05O_3-δ Membranes

Researchers all over the world are actively exploring a kind of reproduceable energy to replace the traditional energy due to the environmental problems caused by oil. Since the hydrogen has advantages of clean, efficient and renewable, it has become an ideal substitute for fossil fuel. Owing to many advantages such as thermal stability, good mechanical strength and high hydrogen selectivity, dense ceramic membranes, mostly based on the Sr Ce O3 and Ba Ce O3 perovskite oxides in a general formula of ABO3, have attracted considerable attention for their potential application for separating H2.In this paper, the In doped Sr Ce0.95-x Inx Tm0.05O3-δ(SCITm) powders were prepared by the sol-gel technique and the SCITm membranes were prepared by pressing followed by sintering. The thermogravimetric(TG), X-ray diffraction(XRD) and scanning electron microscope(SEM) measurements were carried out to study the formation of perovskite structure and the influence of sintering temperature, sintering time and the doping amount of In on the membranes. According to the results of research, the precursor powder sintered at 1000℃ with small particle size is very suitable for pressing. The grain size of the membrane increases with the rising of sintering temperature and the sintering time,and the membrane is the best under 1300℃ sintered 10 h. The effects of In doping on the chemical stability and hydrogen permeation flux of SCTm were investigated. The stability test shows that the stability against CO2 and boiling water increases with the increasing In content, while the hydrogen permeation flux test shows that the content of In doped slightly reduced the hydrogen permeation flux of membranes. Hydrogen permeation through the SCITm membranes was carried out between 700 and 900℃ using 40 % H2/He mixture as feed gas. Activation energies of SCTm, SCITm10 and SCITm20 are 36.61, 52.25 and 73.06 k J/mol, respectively. The decrease of hydrogen permeation flux for the In-doped samples could be induced by the decrease of protonic and electronic conductivity.The In doping reduces the hydrogen permeation of SCTm membrane, while it imporves the stability of SCTm membrane in boiling water and CO2, it is very significative for the practical application. We can reduce the membrane thichness or modify the surface of membrane to offset the reduction in permeation flux which was caused by the In doping.