Reinforcing ion-cluster connectivity via hyperbranched phosphonium units for high-performance and durable AEMWE membranes

Abstract

Anion exchange membrane water electrolysis (AEMWE) technology has been actively researched for the production of green hydrogen as a next-generation clean energy source, with a primary focus on developing high-performance anion-exchange membranes (AEMs). However, the relatively low ionic conductivity and alkaline stability of AEMs can compromise both the performance and durability of AEMWE systems. Recent studies have reported the introduction of branched structures to enhance microphase separation, thereby improving the ionic conductivity and stability of AEMs. In this study, hyperbranched triphenylphosphine units were incorporated into linear poly ( para- terphenyl piperidinium) (QPpTP), and the central phosphorus atom was functionalized into phosphonium (P+), yielding branched polymers with an ion-conducting group as the branched unit (b-QP m -QPpTP, m = 5, 7.5, 10). Triphenylphosphonium introduction enabled strong P+-OH- interactions, simultaneously achieving high water uptake, low swelling ratio, and excellent dimensional stability. Notably, b-QP5-QPpTP exhibited enhanced ion-cluster connectivity and a high OH− conductivity of 155.76 mS cm−1 at 80 °C. It also demonstrated outstanding water electrolysis performance of 6.98 A cm−2 at 2.0 V, as well as excellent long-term durability with a negligible voltage increase of 0.54 mV h−1 over 250 h, confirming its potential as a high-performance branched AEM material for next-generation AEMWE applications.