Numerical modeling of hydrogen permeation in chemical potential gradients

A point defect model was used to describe the functional dependence of defect species in SrCe0.95Y0.05O3−d on hydrogen, water vapor, and oxygen partial pressure. Concentrations of each defect were simulated with a C programming code. The mobilities of protons, oxygen ions, and electrons were evaluated from partial conductivities. Hydrogen permeation equations derived from chemical diffusion theory were solved by a numerical modeling method. Accurate predictions of the hydrogen permeation flux were possible only when the functional dependence of ionic/electronic conductivity on both hydrogen and oxygen partial pressure was known. The dependence of hydrogen permeation flux on hydrogen potential difference agrees with the PH2 dependence of electronic conductivity. Hydrogen permeation flux calculated for 1 mm SrCe0.95Y0.05O3−d was ≈1.50×10−9 mol/cm2 s under ΔPH2 (=10−7–1 atm), PO2 (=10−24–10−12 atm) with the same PH2O (=0.03 atm) on both sides at 973 K.