Synthesis, Oxygen Permeation, and CO₂-Tolerance Properties of Ce_0.8Gd_0.2O_2−δ–Ba_0.95La_0.05Fe_1–<i>x</i>Nb_<i>x</i>O_3−δ Dual-Phase Membranes

Abstract

A series of CO2-tolerant dual-phase dense oxygen permeable membranes of stoichiometry Ce0.8Gd0.2O2−δ–Ba0.95La0.05Fe1–xNbxO3−δ (CG–BLF1–xNx, x = 0, 0.025, 0.05, 0.10, and 0.15) were designed and prepared by the sol–gel method. Their stability regarding phase composition and structure, oxygen permeability, and CO2-tolerant property were investigated by X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC), and temperature-programmed desorption of oxygen (O2-TPD). Results of the materials characterization showed excellent chemical compatibility between CG and BLF1–xNx without the formation of any impurity phase after sintering at 1200 °C in air. The oxygen-permeation experiments showed that with increasing niobium content, the oxygen permeability of the CG–BLF1–xNx membranes decreased slightly, but the compositional and structural stability in CO2 atmosphere improved significantly. The 60 wt % CG–40 wt % BLF0.9N0.1 membrane showed simultaneously good oxygen permeability and excellent CO2 tolerance, and the oxygen-permeation flux reached 0.195 mL·cm–2·min–1 in pure CO2 atmosphere at 925 °C using a 1.0 mm thick membrane. This work demonstrates that CG–BLF1–xNx dual-phase membranes have great application potential for separating oxygen from highly concentrated CO2 atmosphere.