Non-metallic cation and anion co-doped perovskite oxide ceramic membranes for high-efficiency oxygen permeation at low temperatures

Abstract

Insufficient structural stability and limited lattice oxygen mobility at low temperatures seriously limit the application of perovskite-type oxides in mixed ionic-electronic conducting oxygen-permeable membranes. Engineering the crystal structure and oxygen vacancies by ion doping is an effective strategy to enhance both structural stability and lattice oxygen mobility. Different from conventional metal ion doping, we report that the co-doping of the classical SrCoO_3-δ by the non-metallic cation P⁵⁺ and the anion Cl⁻ stabilizes the cubic perovskite structure and allows low temperature oxygen permeation due to improved lattice oxygen mobility. In detail, P doped at the Co site transforms the crystal structure from the hexagonal phase to the cubic phase, and Cl doped at the oxygen site weakens the metal-oxygen bond, which significantly enhances the lattice oxygen mobility. Optimal doping concentrations were found to be SrCo_0.95P_0.05O_3-δCl_0.05 (SCP5Cl5). Furthermore, by constructing an asymmetric membrane with a sandwich structure, the oxygen permeation flux of the SCP5Cl5 ceramic membrane was up to 1.10 mL min⁻¹ cm⁻² at 873 K, which provides an effective strategy for developing oxygen-permeable membranes with high permeation flux at low temperatures.