Effect of zirconium doping on hydrogen permeation through strontium cerate membranes

SrCe_0.95Tm_0.05O_3-δ perovskite-type ceramic membranes offer high hydrogen selectivity, thermal stability, mixed protonic-electronic conductivity, and mechanical strength at temperatures above 600 °C. However, in order for the SrCeO₃-based membranes to be used in industrial applications, the chemical stability of the membranes in various environments must be improved. The effect of doping zirconium on the chemical stability, lattice structure, protonic and electronic conductivity, and hydrogen permeation properties of SrCe_0.95-xZr_xTm _0.05O_3-δ (0 ≤ x ≤ 0.40) was studied. X-ray diffraction analysis verifies that all samples consist of a single perovskite phase. Doping zirconium in SrCe_0.95Tm_0.05O _3-δ results in a decrease in both the protonic and electronic conductivity of the materials under reducing conditions, and a more significant decrease in hydrogen permeability of the membrane in CO₂ free gas streams. In a CO₂-containing environment SrCe_0.75Zr _0.20Tm_0.05O3-δ membranes have a larger steady-state H₂ flux and superior chemical stability over SrCe _0.95Tm_0.05O_3-δ membranes.