Synthesis of an Alkaline-Stable In Situ Cross-Linked Poly(ether imide)-Based Anion Exchange Membrane Electrolyte for Water Electrolyzers and Fuel Cell Applications

Poly(ether imide) (PEI) is a low-cost, easy-to-synthesize anion exchange membrane (AEM) used in energy applications. However, PEI-based AEMs are not highly investigated for anion exchange membrane fuel cells (AEMFCs) and water electrolyzers (AEMWEs) due to their alkaline-susceptible polymer backbone. In this study, a series of cross-linked poly(ether imide)-poly(triphenyl benzene piperidinium) (PEI-PTP-x, x = wt % of PTP) AEMs were prepared for AEMFCs and AEMWEs. Notably, the PEI-PTP-60 membrane reached a maximum hydroxide conductivity of 82.16 mS cm^-1, whereas the pristine PEI membrane reached 35.13 mS cm^-1 at 90 °C. In a H₂/O₂ AEMFC test, the PEI-PTP-60 membrane demonstrated the highest peak power density (PPD) of 210.17 mW cm^-2 with a current density of 707.12 mA cm^-2, whereas the pristine PEI membrane reached a PPD of 156.62 mW cm^-2 with a current density of 506.81 mA cm^-2. In AEMWEs, PEI shows a current density of 825 mA cm^-2 and 1515 mA cm^-2 at 1.8 and 2.0 V, respectively, whereas PEI-PTP-60 shows a current density of 875 mA cm^-2 and 1562.5 mA cm^-2 at 1.8 and 2.0 V, respectively. These results demonstrate a reliable approach to improve the physicochemical and electrochemical characteristics of the poly(ether imide) AEM electrolyte for use in AEMWEs and AEMFCs.