Bidirectional Reinforcement of the CoAl-LDH-Doped Poly(aryl ether nitrile) Anion Exchange Membrane for Water Electrolysis

Poly(aryl ether)-based anion exchange membranes (AEMs) exhibit an alternative choice for sustainable hydrogen production through anion exchange membrane water electrolysis (AEMWE). However, the nucleophilic attack of OH– on ether bond under alkaline condition leads to membrane degradation, which remains a core technical bottleneck. To overcome this challenge, we herein develop a dual strategy, which combines the molecular structure design and nanofiller reinforcement, to prepare the highly conductive and durable poly(aryl ether nitrile)/LDH composite AEMs. At the molecular level, the high-free-volume monomer is introduced to expand chain segment spacing of AEM, while chemical cross-linking is implemented to simultaneously construct well-defined OH– conduction pathways and enhance structural stability. Moreover, the doping of a CoAl-layered double hydroxide (LDH) forms a synergistic interface with the poly(aryl ether nitrile) (PAEN) matrix. The positively charged LDH layers interact with the imidazolium cation of AEMs to establish an ordered electrostatic network, while surface hydroxyl groups engage in extensive hydrogen bonding with hydrophilic functional groups in the polymer, thereby building a continuous hydrogen-bonded pathway. These dual interactions efficiently improve the continuity of OH– transport and enhance interfacial compatibility between the filler and matrix. Notably, the CoAl-LDH0.6@VPAENF membrane achieves an OH– conductivity of 135.32 mS/cm at 80 °C. When assembled into a membrane electrode assembly (MEA) for AEMWE operation at 60 °C, it delivers a maximum current density of 2.40 A/cm2 within the voltage range of 0–2 V and maintains stable operation at 250 mA/cm2 for 180 h with a low voltage decay rate of only 0.387 mV/h. This work provides robust theoretical and experimental support for the rational design of durable AEMs in strong alkaline conditions and advances their practical implementation in a hydrogen production system.