H2SO4 stability of PBI-blend membranes for SO2 electrolysis

Evaluation of covalently and ionically cross-linked PBI-excess blends for application in SO2 electrolysis

“…An alternative membrane material that has shown its suitability at these temperatures are polybenzimidazole (PBI) based membranes [6]. These types of membrane require the presence of an acid to facilitate the conduction of protons across the membrane [7]. The sulfonation of a partially fluorinated (sFS) arylene, blended with commercial PBI, has been shown to produce a thermal and chemical stable proton exchange membrane for use in the SO 2 electrolyser environment.…”

“…Firstly both types of membranes are tested for acid stability [7,8] simulating the acidic environment of the electrolyser. Weight change, swelling and FTIR analysis are used to characterise the effect that the acidic medium have on the membranes.…”

Sulfonated poly(arylene thioether phosphine oxide)s and poly(arylene ether phosphine oxide)s PBI-blend membranes and their performance in SO2 electrolysis

“…It is also clear that the MEA of membrane MKA16 had an excellent thermal stability, since considerable degradation only started at about 450 C. For both MEAs, the degradation proceeds in two major steps; between 300 and 450 C which is related to the splitting off of the eSO 3 H groups and between 450 and 600 C which is related to backbone degradation. The slight deviations before and after SO 2 electrolysis could be correlated to the slight sulfonation of the membranes during the SO 2 electrolysis experiment (a phenomena that had been observed during the H 2 SO 4 stability tests described both above and previously [13]). This means that the total sulfonic acid group content of the membranes after electrolysis should increase which can lead to higher weight loss in the temperature range where the sulfonic acid groups are split off, i.e.…”

“…Both MKA20 and MKA21 became lighter during H 2 SO 4 treatment while becoming harder and more brittle. It can be assumed that during H 2 SO 4 treatment, the PBIOO might have formed hydrogensulphate salts by imidazole protonation as discussed previously [13]. In contrast to the behaviour in H 2 SO 4 , the membranes MKA20 and MKA21 turned much darker and became harder in H 3 PO 4 .…”

“…This membrane type has been applied in H 2 fuel cell (H 2 PEMFC) membranes up to T ¼ 100 C [9] and direct methanol fuel cell (DMFC) membranes up to T ¼ 130 C [10]. Recently, acid-excess acid-base blend membranes have also been used in the HyS process and showed similar, partially even better performance than the PFSA benchmark materials [13]. It can be assumed that when applying the PBI membranes to the SO 2 electrolysis process, the sulfuric acid electrolyte present in the electrolysis cell dopes the PBI membrane thereby contributing to the proton conduction in the membrane (schematically represented in Fig.…”