Synthesis of Mixed Oxide-Ion and Carbonate-Ion Conductors Supported by a Prefabricated Porous Solid Oxide Matrix

A novel two-step approach is used to fabricate a two-phase mixed oxide-ion and carbonate-ion conductor (MOCC) that has been recently developed for intermediate temperature solid oxide fuel cells (IT-SOFCs) and CO₂ separation membranes. In this study, a samarium doped ceria (SDC) is selected as an example to demonstrate the prefabrication of porous matrix by the “sacrificial template” methodology with NiO as the template material. NiO has been reduced into elemental Ni in the composite, and then removed by dissolving into a nitric acid. It was demonstrated by XRD, EDS and weight changes. The microstructure of the SDC matrix characterized with an SEM imaging reveals a uniform distribution of homogeneous micro-pores across the solid-oxide matrix. The strong porous solid-oxide matrix is prefabricated at high temperature, into which a molten carbonate phase is subsequently infiltrated. A Li-Na-carbonate-impregnated MOCC supported by a 41.8% porous SDC matrix shows an effective ionic conductivity of 0.43 S/cm at 650 °C.