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.