Development of phosphonium-based bicarbonate anion exchange polymer membranes

• Phosphonium bicarbonate anion exchange membranes (AEMs) were prepared.
• Bicarbonate AEMs compare well with chloride AEMs.
• A detailed chemical degradation mechanism for bicarbonate AEMs is presented.

We report the preparation and characterization of phosphonium-based bicarbonate anion exchange random copolymers, poly(styrene-random-trimethylvinylbenzyl phosphonium bicarbonate) (poly(S-r-TMVBP-HCO3)). Compared to the chloride anion (Cl−) exchange membranes, these HCO3− exchange membranes exhibit similar hydration levels and only slightly lower ionic conductivities at similar ionic compositions. Other experiments reveal that the HCO3− exchange membranes are thermally stable (up to 110 °C) and chemically stable under relatively low alkaline conditions. Additionally, a detailed chemical degradation mechanism for these membranes under strong alkaline conditions is presented.