Semi-interpenetrating polymer network ion-solvating membrane with enhanced conductivity and stability for potential application in alkaline water electrolysis

Abstract

This study presents a new semi-interpenetrating polymer network (semi-IPN) membrane, combining polyvinyl alcohol (PVA) cross-linked with citric acid (CA) and physically entangled with of polyvinylpyrrolidone (PVP) via solvent casting. To achieve a suitable balance between ionic conductivity, mechanical stability, and long-term chemical resistance, a series of PVA-CA:PVPX membranes were synthesized and subsequently subjected to thermal curing and KOH doping. Optimized PVP content stabilizes the semi-IPN structure by reinforcing H-bonding with PVA, resulting in a well-entangled polymer matrix. However, excessive PVP disrupts polymer chain interactions, leading to excessive microphase separation, extreme swelling, and diminished mechanical integrity. Thermal curing further strengthens crosslinking, enhancing mechanical properties (1270 MPa tensile modulus, 413% elongation) while controlling water uptake (193.96%). Additionally, KOH doping introduces carboxylate groups, increasing OH⁻ mobility (6.56 mS cm⁻¹) and improving electrochemical performance. The optimized membrane demonstrates high oxidative stability, retaining 90.90% of its mass after prolonged exposure while maintaining structural integrity over three months in alkaline conditions. Furthermore, its enhanced thermal stability extends operational lifespan under elevated temperatures, making it a promising candidate for long-term electrolysis applications. These findings establish semi-IPN structuring as an effective strategy for developing high-performance membranes suited for next-generation alkaline water electrolyzers.