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

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 degrees 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 m Omega cm(-2) and electrolyser current density of 814 mA cm(-2) at 2.0 V in 0.1 M NaOH solution at 40 degrees C. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Cross-linked quaternised Poly(2,6-dimethyl-1,4-Phenylene Oxide) (QPPO)-based membranes were prepared with environmentally-friendly chloromethylating reagents, showing high ionic conductivity. The membranes exhibited good performance and mechanical stability in AEM water electrolyser applications.