Synthesis, characterization and water electrolyzer cell tests of poly(biphenyl piperidinium) Anion exchange membranes

Water electrolyzers based on anion exchange membranes (AEM) enable the use of platinum group metal-free catalysts, substantially lowering the capital costs of this technology and thereby reducing the price of green hydrogen. Their industrial adoption is limited by the poor durability of AEMs, precluding long term operation. A very promising class of AEMs in terms of stability are poly(aryl piperidiniums)s (PAPs), which combine an heteroatom free backbone with the stable piperidinium cationic group. The simplest and less expensive chemistry in this family is based on poly(biphenyl piperidinium), which has so far been considered unsuitable for membrane fabrication due to poor mechanical properties. Through optimized polymerization parameters we obtained mechanically resistant films down to a thickness of 15 μm. The membranes reach an ambitious conductivity of 185 mS cm−1 (80 °C, 100% RH) with almost no degradation signs after 360 h in 1 M KOH at 80 °C. Importantly, we demonstrate their viability in an electrolyzer cell, outperforming a PAP-based commercial membrane. We believe that these results present strong potential for not expensive AEMs with an easy synthesis, that will serve as a benchmark for further optimization of PAP-based polymers.