Modeling hydrogen permeation through a thin titanium oxide film and palladium

Abstract Models that describe hydrogen permeation through a thin TiO2 film deposited on Pd have been developed based on a mass-balance equation consisting of diffusion, reversible hydrogen absorption/desorption, and irreversible hydrogen trapping. These models were numerically simulated by the finite element method. By comparing model simulations with experimental permeation curves, values of the parameters associated with permeation, such as diffusion coefficients, absorption and desorption rate constants, trapping rate constants, and saturation concentrations, can be evaluated. The TiO2 film noticeably impedes hydrogen permeation, essentially due to slow hydrogen transport in the oxide. The diffusion coefficient of hydrogen in TiO2 was found to be 10− 13 cm2/s, three orders of magnitude lower than that in Ti metal.