Highly conductive partially cross-linked poly(2,6-dimethyl-1,4-phenylene oxide) as anion exchange membrane and ionomer for water electrolysis

• Published in: International journal of hydrogen energy 2021-10, Vol.46 (75), p.37137-37151
• Main Authors: Feng, Zhiming, Esteban, Pilar Ocón, Gupta, Gaurav, Fulton, David A., Mamlouk, Mohamed
• Format: Article
• Language: English
• Subjects: AEM; Friedel-crafts reactions; Poly(2,6-dimethyl-1,4-phenylene oxide); PPO; Water electrolyser
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2021.09.014

Cross-linked quaternised Poly(2,6-dimethyl-1,4-Phenylene Oxide) (QPPO)-based membranes were prepared via Friedel-Crafts reactions using SnCl4 catalyst, 1,3,5-trioxane and chlorotrimethylsilane as environmentally-friendly chloromethylating reagents. New equations to calculate the degree of chloromethylation (DC) and cross-linking degree (CLD) were proposed. Ionic conductivity of 133 mS cm−1 at 80 °C was obtained, one of the highest reported for QPPO based membranes. We have compared QPPO to chloromethylated polystyrene-b-poly(ethylene/butylene)-b-polystyrene (SEBS) ionomer and report on the importance of ionomer-membrane interaction as well as the trade-off between swelling ratio and conductivity on performance and mechanical stability of AEM water electrolyser. Exsitu stability testing after 500 h in 1 M KOH showed membranes retained up to 94% of their original IEC. QPPO was employed as both membranes and ionomers in electrolyser tests. QPPO membranes exhibited area specific resistance of 104 mΩ cm−2 and electrolyser current density of 814 mA cm−2 at 2.0 V in 0.1 M NaOH solution at 40 °C. [Display omitted] •New equations to calculate the degree of chloromethylation (DC) and cross-linking degree (CLD).•Synthesis and fabrication of self-crosslinking PPO based AEM with ionic conductivity >0.13 S cm−1.•Electrolyser current density of 814 mA cm−2 at 2.0 V at 40 °C.•Area specific resistance of 104 mΩ cm−2 in 0.1 M NaOH solution at 40 °C.