Synthesis, CO2-tolerance and rate-determining step of Nb-doped Ce0.8Gd0.2O2−δ-Pr0.6Sr0.4Co0.5Fe0.5O3−δ ceramic membranes

In this work, CO2-tolerant Ce0.8Gd0.2O2δ-Pr0.6Sr0.4Co0.5Fe0.5−xNbxO3−δ (CG-PSCF0.5−xNx; x=0-0.125) dual-phase dense oxygen permeation membranes were successfully developed. The crystal structure, microstructure, oxygen permeability, rate-determining step and CO2 tolerance were systematically investigated. The experimental results showed that the increase in CG content improved oxygen permeability and CO2 tolerance. Thermogravimetry-differential-scanning-calorimetry analysis, X-ray photoelectron spectra and oxygen permeation tests indicated that the increase in Nb content caused a slight decrease in oxygen permeability, while the long-term CO2 resistance can be improved significantly. According to the adopted permeation model, the weight ratio and thickness affect the oxygen permeability and permeation resistance distribution. By examining the distribution of three permeation resistances, we identified the rate-determining step and then optimized the weight ratio of the two phases, as well exploring the effects of thickness on oxygen permeability. All these experiments confirm that CG-PSCF0.5−xNx dual-phase membranes have great CO2 tolerance and potential application in oxy-fuel combustion.