Understanding the doping effect toward the design of CO₂-tolerant perovskite membranes with enhanced oxygen permeability

Most perovskites possessing high oxygen permeability always suffer from low chemical stability under CO₂-containing conditions. A comprehensive knowledge for improving the resistance toward CO₂ through doping strategy is still lacking. In this work, we propose a series of perovskite oxides, i.e., SrFe_0.8M_0.2O_3−δ (M=Ti⁴⁺, Nb⁵⁺, and Cr⁶⁺), and systematically investigate the effect of dopants with the high oxidation state on the phase structure, chemical stability, sintering behavior, conducting properties, and oxygen permeability. The oxygen permeability and the CO₂ tolerance of the membranes are closely related to the oxidation state of the dopants for altering the oxygen vacancy concentration, the oxidation state of Fe ions and the average metal-oxygen bond energy. The balance of oxygen permeability and the CO₂ tolerance should be taken into account during practical application. This work thus provides useful guidelines for the future development of perovskite oxides through B-site doping for efficient air separation.