Advancing electrochemical measurements of the hydrogen diffusion, solubility, and permeability in polymers

Abstract

In hydrogen technologies, polymers play a key role due to their chemical corrosion-resistance and mechanical robustness. Yet, reported data characterizing hydrogen permeation in polymers are scarce. In this work, the methodology for electrochemical measurements of hydrogen permeation through polymers is improved and applied to determine the temperature dependence of hydrogen permeability, diffusion coefficient, and solubility of polypropylene, polytetrafluoroethylene, polyphenylene sulfide, polyether sulfone, and polyether ether ketone. Sputtered palladium films on the polymers act as hydrogen oxidation catalysts, while the transient oxidation current during a hydrogen pressure drop is measured. The time dependence of the measured permeation rates is fitted to numerical simulations based on Fick's second law, allowing to determine diffusion coefficients, solubilities, and permeabilities. This procedure increases precision compared to the state-of-the-art time lag method, which relies on a simplified analytical model. The observed differences in hydrogen transport are related to the structural and physicochemical properties of the polymers.