Novel cross-linked partially fluorinated and non-fluorinated polyaromatic PBI-containing blend membranes for SO2 electrolysis

Various partially fluorinated and non-fluorinated polyaromatic and PBI blend components were covalent-ionically cross-linked to obtain proton exchange membranes that can be applied in an SO2 electrolyser. During SO2 electrolysis, SO2 and H2O are converted to H2 and H2SO4, which implies that the membranes to be used for this process should have both a high proton conductivity and H2SO4 stability. The acid stability of the blend membranes were evaluated in an 80 wt% H2SO4 environment for 120 h at 80 and 95 °C respectively. From the characterization results obtained by monitoring weight and thickness change, IEC, SEM-EDX and TGA signal's before and after treatment, it was determined that the novel cross-linked blend membranes, containing only partially fluorinated polymer components, showed exceptional stability. The cross-linked partially fluorinated polyaromatic PBI blended membrane (SFS001-F6PBI-BrPAE) and Nafion® 115 were selected for electrochemical evaluation by obtaining polarization curves at 80 and 95 °C. The SFS001-F6PBI-BrPAE performed the best at operation temperature of 95 °C reaching a current density of 0.63 A cm−2 in comparison to the 0.42 A cm−2 obtained for Nafion® 115 at 1.0 V. Durability of the membranes within the electrolyser were measured by means of voltage stepping and subsequent characterization using SEM-EDX, TEM and TGA which confirmed the minimal degradation observed for the 250 cycles completed.