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 typical polyelectrolyte membrane, leading to keep high permselectivity in wet conditions. By optimizing the structure of the proposed polymer membrane, it is expected to exhibit better separation performance.