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 P-H2 dependence of electronic conductivity. Hydrogen permeation flux calculated for 1 mm SrCe0.95Y0.05O3-d was approximate to 1.50 x 10(-9) mol/cm(2) s under DeltaP(H2) (= 10(-7)-1 atm), P-O2 (= 10(-24)-10(-12) atm) with the same P-H2O (= 0.03 atm) on both sides at 973 K. (C) 2003 Elsevier B.V. All rights reserved.