Composite anion exchange membranes based on poly(biphenyl piperidinium) / ZrO2

The main requirement for the development of Anion Exchange Membranes Fuel Cells (AEMFCs) and Water Electrolyzers (AEMFEs) on an industrial scale is the improvement of Anion Exchange Membranes performance. Besides good ionic conductivity, dimensional stability and mechanical properties in the wet state, the main challenge to be overcome is the improvement of AEMs chemical resistance in harsh alkaline environment. Poly(aryl piperidinium)s are among the most promising AEMs in terms of conductivity, mechanical properties, and chemical stability. Here we report the fabrication and physico-chemical characterization of composite AEMs based on poly(biphenyl piperidinium) (PBP) with the addition of zirconium oxide as a filler to improve membrane properties, including anionic conductivity, water uptake and alkali resistance. The optimal ZrO₂ filler content was found to be 5 wt% of dry polymer mass. Compared to plain PBP, composite membranes exhibit increased hydroxide conductivity (from 75 to 116 mS cm⁻¹ at 80 °C), reduced water uptake (from 427 % to 278 % at 80 °C) and swelling ratio (from 85 to 62 % at 80 °C), and a limited reduction (41 %) of cationic groups after ageing in KOH 1 M for 500 h at 80 °C. We demonstrate that ZrO₂ filler hinders Hoffman elimination reaction on the piperidinium ring.