A polyfluorene-based electrolyte membrane for hydrogen/oxygen gas separation under humidified conditions†

Abstract

Hydrogen/oxygen separation under wet conditions has recently become important in the production of hydrogen. This study developed an electrolyte membrane, PFST-C8-SO3H, with a poly(fluorene-alt-tetrafluorophenylene) backbone and achieved high hydrogen/oxygen separation performance under wet conditions. Polymer membranes with a normal aromatic backbone frequently exhibit high rigidity and low gas permeability due to π stacking. However, by introducing a long alkyl sulfonic acid side chain and a three-dimensionally twisted structure into the skeleton, it had a high free volume and a specifically high permeability for hydrogen. The membrane shows lower water vapor absorption than a typical polyelectrolyte membrane, leading to retain high permselectivity under wet conditions. By optimizing the structure of the proposed polymer membrane, it is expected to exhibit better separation performance.