Novel Composite Cermet for Low-Metal-Content Oxygen Separation Membranes

A dense composite of silver and Ce 0.8 Sm 0.2 O 2−δ (Ag-CSO) was manufactured from ceramic nanoparticles coated by electroless deposition of silver. At 700 °C, a 1-mm-thick membrane of the composite delivered an excellent oxygen permeation rate from air with a value of 0.04 μmol cm –2 s –1, using argon as the sweep gas and 0.17 μmol cm –2 s –1 using hydrogen. The low sintering temperature of the CSO nanoparticles allows the use of Ag rather than Pt or Pd and reduces the amount of metal needed for electronic conductivity to just 5.6 vol %, which is lower than any value reported in the literature. Oxygen diffusivity measurements confirmed that the oxygen migration remained high in the composite, with an increase in surface exchange coefficient of three orders of magnitude over Gd-doped ceria. The ease of membrane fabrication, combined with encouraging oxygen permeation rates, demonstrate the promise of the material for high-purity oxygen separation below 700 °C.