Ionic liquid-functionalized graphene oxide-reinforced-poly(carbazole) nanocomposite anionic membranes for high-performance water electrolysis

Abstract

Anion exchange membrane water electrolysis (AEMWE) promises low-cost green hydrogen production but is limited by the anion exchange membranes (AEMs) that must couple high hydroxide (OH⁻) ion conductivity (IC) with mechanical robustness and alkaline durability. Rigid ether-free poly(carbazole) (PC) backbones help stability, yet transport-swelling trade-offs still cap performance. This study reported ionic liquid-functionalized graphene oxide (ILQ-FGO)-reinforced quaternized poly(carbazole) (QPC) nanocomposite AEMs that integrate a chemically resilient backbone with a cationic two-dimensional (2D) nano-filler to build percolated ion pathways while suppressing excessive swelling. All the AEMs demonstrated a balanced performance of dimensional, mechanical, and electrochemical stability. The optimized QPC-ILQ-FGO-1.5 AEM exhibited the highest IC of 279.3 mS cm⁻¹ at 80 °C, which is approximately a two-fold increase compared to the pristine QPC membrane (156.2 mS cm⁻¹). This membrane also exhibited an impressive single-cell performance, having a peak current density of 4.61 A cm⁻² at 2.0 V in 1 M KOH at 60 °C. The mechanical testing suggested an increased tensile strength of 51.55 megapascal (MPa), while alkaline aging (1 M KOH, 60 °C, 504 h) shows ≥92% IC retention by this membrane. The long-term durability testing further validates the robustness of AEMs with a minimal voltage decay rate of 0.35 mV h⁻¹ up to 240 h of stable water electrolysis operation. In summary, the weaving of cation-rich ILQ-FGO into a rigid QPC polymer matrix reconciles the classical transport-stability trade-off, enabling high IC, mechanical strength, and alkaline durability in a scalable platform for advancing high-performing AEMWE technologies.