Lower Temperature Electrolytic Reduction of CO[sub 2] to O[sub 2] and CO with High-Conductivity Solid Oxide Bilayer Electrolytes

Abstract

Ceramic oxygen generators (COGs) with a bilayer-electrolyte (erbia-stabilized bismuth oxide/samaria-doped ceria) architecture were developed to produce pure oxygen from CO 2 at lower temperature (below 700°C) for potential use in NASA's Mars exploration mission. Major factors that influence oxygen generation include the oxygen-ion conductivity of the solid-oxide electrolyte, applied current, operating temperature, and fuel utilization (CO/CO 2 ratio). The COG voltage power losses were due to internal resistance and electrode polarization. Higher temperatures resulted in higher oxygen generation rates due to reduced cell resistance. However, lowering the COG operating temperature is very important and the bilayer COGs showed promise for operation below 700°C, thus reducing the required power consumption, expanding ancillary material selection, decreasing fabrication cost, and potentially extendingmission time. © 2005 The Electrochemical Society. All rights reserved.