Comparison of ionically and ionical-covalently cross-linked polyaromatic membranes for SO2 electrolysis

•PBI-based membranes proved thermal and chemically stable after H2SO4 treatment.•Improved acid stability of SFS-PBI due to partially fluorinated PBI component.•Improved HyS electrolysis performance at current densities below 0.3 A/cm2.

It has been shown that hydrogen, which can be used for energy storage, can be produced efficiently by the membrane based Hybrid Sulfur (HyS) process. During the HyS electrolysis step, SO2 and H2O are converted to H2 and H2SO4, which implies that membranes to be used for this process should have both a high proton conductivity and acid stability. In this study ionic and ionic-covalently cross-linked polybenzimidazole (PBI) blended membranes were investigated and compared with Nafion®212 in terms of their acid stability. Characterization of the membranes, which included monitoring the change in weight, swelling, SEM/EDX, TEM, TGA-MS, FTIR and IEC before and after H2SO4 treatment showed that all tested membranes were stable in 80 wt% H2SO4 at 80 °C for 120 h. Subsequent HyS electrolysis showed that the blend membranes performed better than Nafion®115 at current densities below 0.3 A/cm2, while performing similar above 0.3 A/cm2.