Gd0.2Ce0.8O1.9-Y0.08Sr0.88Ti0.95Al0.05O3 + δ Composite Mixed Conductors for Hydrogen Separation

Abstract

A new approach to separate hydrogen using oxygen ion and electron/hole mixed conductors has been proposed and is being currently investigated. In this approach, oxygen from steam diffuses across the membrane as ions through coupled transport with electrons/holes, resulting in conversion of the steam into hydrogen. Methane reformation by the transported oxygen occurs on the other side of the membrane. While doped lanthanum strontium cobalt iron oxides possess high mixed conductivity under relatively oxidizing conditions, they do not sustain these conductivities under relatively reducing conditions. Further, they are unstable under the relatively reducing conditions expected to prevail on both sides of the membrane in the current process. A new dual-phase composite mixed ionic and electronic conducting (MIEC) membrane, comprised of doped ceria, an excellent oxygen-ion conductor, and doped strontium titanate, an excellent electronic conductor, has been developed. This dual-phase composite is stable in very reducing conditions and suitable for application in the proposed hydrogen separation process. The physical and electrical characterization of the composite comprising doped ceria and doped strontium titanate has been investigated in this study.