Physical–Chemical Cross-Linked Amphoteric Ion-Exchange Membranes for Energy-Efficient Acid–Alkaline Water Electrolysis

Abstract

Acid–alkaline amphoteric water electrolysis is highly promising for energy-efficient hydrogen production, yet navigating the trade-off between membrane conductivity and long-term stability remains challenging. Herein, we propose a “physical–chemical” crosslinking strategy to engineer robust amphoteric ion-exchange membranes (MDAPPO2-Y). The sulfonic acid groups and quaternary ammonium groups form an ion pairing structure, which contributes to constraining hydrated ionic domains, promotes microphase separation, and facilitates ion transport. In addition, the constructed three-dimensional chemical crosslinking network further enhances the dimensional stability and mechanical properties of the membranes. Specifically, the MDAPPO2-0.1 AIEM exhibits good mechanical properties (tensile strength of 30.26 MPa) and a water uptake of 65.83% at 80 °C, achieving high proton conductivity (127.09 mS·cm–1) and hydroxide conductivity (57.83 mS·cm–1) while maintaining dimensional stability. In acidic and alkaline stability tests, the conductivity retention of the MDAPPO2-0.1 AIEM reaches 79.09 and 73.50%, respectively. In water electrolysis tests, a current density of 603 mA·cm–2 is achieved at 2.0 V, significantly outperforming the commercial Nafion 115 membrane. These results demonstrate that the developed high-performance amphoteric ion exchange membrane holds good application potential for acid–alkaline amphoteric water electrolysis.