Cross-Linked Anion Exchange Membranes Based on Poly(diphenyl sulfide piperidine)s with Good Comprehensive Performance for Water Electrolysis

In this work, a series of cross-linked anion exchange membranes (AEMs) based on poly(diphenyl sulfide piperidine)s (PPSP35-Cox) are designed and prepared. The comprehensive performance of these membranes is significantly enhanced by introducing hydrophobic alkyl chains as cross-linked agents and optimizing the degree of cross-linking. The cross-linked structure effectively inhibits the swelling ratio (SR), improves the dimensional stability and mechanical strength, and also enhances the OH– conductivity. The SR for the representative PPSP35-Co50 membrane is controlled at 7.0%–12.4% within 20–80 °C. Its OH– conductivity is up to 160.9 mS cm–1 at 80 °C, and the tensile strength is raised to 59.79 MPa. After immersion in 2 M NaOH solution for 1200 h at 80 °C, the OH– conductivity retention rate is 91.7%, demonstrating excellent alkaline resistance and stability. Additionally, the electrolyzer assembled with PPSP35-Co50 achieves a current density of 2200 mA cm–2 at 80 °C, 2.0 V operating voltage, and 1 M KOH solution, 1.61 times higher than that of the non-cross-linked membranes in the same operating environment. This type of cross-linked membranes have a wide range of potential applications and provide important support for the application of AEM in water electrolysis hydrogen production technology.