Dual Phase Nano-Composite Pt-Cgo Tubular Membranes for O2 Separation

O₂ permeation through metal-electrolyte dual phase composites takes place by commensurate transport of electrons in the metallic, and O^2- in the electrolyte phase; both phases are percolative.  O₂ decomposes into, or recombines from O^2- and electrons at the surface.  Transport of charged species in the membrane phase occurs mostly near the dual phase boundaries.  Hence dense, nano-structured dual-phase membranes show promise for stable, high-flux O₂ separation at temperatures as low as 400°C.  This is due to their pO₂-independent structure, and high concentration of dual and triple phase boundaries.  We studied membrane materials with Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte, and Pt metal.  CGO is oxygen ion-conducting due to the presence of aliovalent Gd³⁺, which causes a high concentration of charge-compensating O^2- vacancies.  To realize a bipercolative structure, a thin meso-porous CGO layer is first deposited on a smooth, defect-free porous α‑alumina compact.  A porous CGO/Pt membrane is prepared by colloidal deposition of CGO/Pt precursor nano particles on the CGO layer, followed by calcination, and densification by electroless growth of additional Pt.