Modeling hydrogen permeation through a thin titanium oxide film and palladium

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. - Highlights: ► Hydrogen permeation through a thin TiO₂ film deposited on Pd was modeled. ► The model includes hydrogen diffusion, absorption and trapping. ► Model simulations were compared well with experimental results. ► This TiO₂ film noticeably impedes hydrogen permeation. ► The diffusion coefficient of hydrogen in this TiO₂ is 10⁻¹³ cm²/s