Systematic experimental assessment of concentration polarization and inhibition in Pd-based membranes for hydrogen purification

In this work, we show the application of a systematic general experimental analysis to estimate in a relatively easy way the paired effects of concentration polarization and inhibition in the hydrogen permeation through diverse supported Pd-based membranes as functions of temperature and mixture composition. For this purpose, three different membranes are fabricated and tested under pure‑hydrogen and binary-mixture of H₂-N₂ and H₂-CO. The former mixture is used to quantify the concentration polarization influence only, whereas the latter is used to quantify the overall combined effect of polarization and inhibition. Manipulating the two effects, we finally obtain the influence of inhibition only. As main results, a maximum overall permeation reduction of around 35%, 55% and 45% is evaluated for Mem#1, for Mem#2, for Mem#3, respectively. Moreover, a maximum concentration polarization coefficient of around 2.5%, 19% and 12% and a maximum inhibition coefficient of 32%, 45% and 40% are respectively evaluated. These values state the importance of having a tool able to take into account these detrimental phenomena in designing ultra-thin-membrane equipment, remarking that the same approach can be applied to other types of metal membranes as well.