ZrO2-Embedded Crosslinked Poly(aryl piperidinium) Membranes with Enhanced Mechanical and Alkaline Stability for Anion Exchange Membrane Water Electrolyzers

Abstract Developing high-performance anion exchange membranes (AEMs) for water electrolyzers (AEMWEs) is essential for low-cost, carbon-free hydrogen production. However, current AEMs are often limited by poor alkaline stability and a trade-off between mechanical strength and ionic conductivity, restricting the long-term stability of AEMWEs. Here, we develop robust AEMs by combining crosslinking of poly(aryl piperidine) (PAP) with the incorporation of nano zirconium dioxide (ZrO2) particles. The PAP backbone was synthesized from N-methyl piperidone, terphenyl, biphenyl, and 1,1,1-trifluoroacetophenone via superacid-catalyzed Friedel–Crafts alkylation, then crosslinked with 1,3,5-benzenetricarbonyl trichloride (0.5–10%) and loaded with nano ZrO2 (0.5–5%). The resulting nano-ZrO2-doped crosslinked PAP AEMs (Zr@CPAPs) show low water uptake (<40%), low swelling ratio (<12%), and high ionic conductivity (120 mS/cm) and sustain stable AEMWE operation for 1500 h with a voltage decay rate of only ∼0.053 mV/h, outperforming the non-crosslinked, undoped membrane. A PPS-supported membrane of 1Zr@7CPAP-80 showed comparable durability, sustaining 0.076 mV/h decay over an extended 2000-hour period. Degradation under alkaline conditions proceeds mainly via oxidative degradation and Hofmann elimination, involving C–N bond cleavage and alkene byproduct formation. Together, these results show that combining rigid crosslinking with ZrO2 doping is a robust, substrate-adaptable strategy for durable, low-voltage-decay AEMs suited to practical AEMWE applications.