Novel mixed conducting SrSc_0.05Co_0.95O _3-δ ceramic membrane for oxygen separation

A novel perovskite-type mixed-conducting oxide of SrSc _0.05Co_0.95O_3-δ (SSC) was synthesized by a combined EDTA-citrate complexing method. The 5 mol % of Sc³⁺ doping into the B-site of SrCoO_3-δ (SC) through the sol-gel synthesis effectively stabilized the oxygen vacancy disordered cubic perovskite structure of the oxide, and simultaneously resulted in a substantial increase of the electrical conductivity. The oxide was fabricated into dense ceramic membrane for oxygen separation by pressing/sintering process. The oxygen permeation flux of the SSC membrdne and the rate-determination step of the permeation process were investigated between 750 and 900°C. The experimental results demonstrated that SSC is a promising membrane for oxygen separation with ultrahigh permeation fluxes, compared favorably with reported high oxygen semipermeable Ba_0.5Sr_0.5Co_0.8Fe _0.2O_3-δ and SrCo_0.8Fe_0.2O _0.δ membrdnes under air/helium gradient. At the condition of reduced temperature and low oxygen partial pressure at the sweep side atmosphere, the permeation process was found to be rate-determined mainly by the slow oxygen surface exchange kinetics at the air (feed) side membrane surface based on the single cell oxygen permeation study. The activation energy for the oxygen surface exchange and oxygen bulk diffusion was found to be around 126 kJ mol^-1 and ≤62.1 kJ mol^-1, respectively.