Poly(carbazole)-Based Anion Exchange Membranes Developed by Grafting Alkyl Ammonium Group

Abstract

AEM water electrolysis offers several advantages over proton exchange membrane water electrolysis such as the potential use of non-precious metal catalysts and less expensive bipolar plates. Therefore, there is a great demand for reliable, high-performing, durable, and low-cost AEMs for the technologies.1 In this presentation, we report polycarbazole-based AEMs by acid-catalyzed Friedel Craft’s polycondensation reaction followed by grafting with an alkyl ammonium group.2 Two AEMs, PDPC-3QA (IEC=1.25 meq./g) and PDPC-6QA (IEC=1.74 meq./g), were synthesized by grafting 3-bromo-N,N,N-trimethylpropan-1-aminium bromide (3-BrQA) and 6-bromo-N,N,N-trimethylhexan-1-aminium bromide (6-BrQA), respectively on the precursor polymer. While 100% grafting was achieved with 6-BrQA, only 60% of grafting was achieved with 3-BrQA due to the competition between the elimination and substitution reaction on 3-BrQA because of the higher acidity of β-hydrogen resulted from the proximity of the bromide and ammonium groups. With high OH- conductivity (103 mS/cm at 80 °C) and excellent alkaline stability (< 3% conductivity loss after 500 hours in 1 M NaOH at 80 °C), PDPC-6QA exhibits promising water electrolyzer performance.