A "Mesh-Type" Branched Poly(aryl piperidine) Anion Exchange Membrane with Excellent Ionic Conductivity for Use in Water Electrolysis.

Abstract

In water electrolysis, the challenge of achieving both high ionic conductivity and stability in anion exchange membranes (AEMs) has significantly hindered the large-scale production of green hydrogen. To address this challenge, this study prepared a series of "mesh-type" branched poly(biphenyl-<i>co</i>-benzyl pyrimidine) (QPBZP-b-<i>x</i>) AEMs. This design achieves a high free volume fraction (FFV) by introducing a branched structure containing heteroatom TPA, thereby reducing the hindrance to OH^- transport within the membrane. Among these, QPBZP-b-32 demonstrates the most outstanding performance, achieving an OH^- ion conductivity of 146.39 mS cm^-1 at 80 °C while maintaining excellent mechanical properties (tensile strength of 42.49 MPa). After undergoing an alkali stability test in 2 M NaOH solution at 80 °C for up to 1500 h, it still retains 84.9% of its OH^- ion conductivity, and after treatment in 5 M NaOH for 200 h, its mechanical properties retain 86% of the original value. Additionally, the anion exchange membrane water electrolysis (AEMWE) based on QPBZP-b-32 achieves a current density of 1.11 A cm^-2 (2.0 V, 1 M KOH). The AEMWE operated stably for 200 h at a constant current density of 0.5 A cm^-2. These results demonstrate that QPBZP-b-<i>x</i> membranes exhibit broad application prospects in AEMWEs.