This study presents the successful development of multiblock copolymer-based crosslinked membranes incorporating 6F-bisphenol-A (6F-BPA)-derived novolac epoxy resin (EFN) for proton exchange membrane fuel cell (PEMFC) applications. To further enhance their functional properties, self-synthesized carboxyl-functionalized carbon nanodots (f-CNDs) were incorporated into the polymer matrix at varying concentrations (0.5, 0.7, and 0.9 wt.%), resulting in nanocomposite membranes. Morphological analyses using FE-SEM and HR-TEM revealed homogeneous dispersion of f-CNDs and well-defined nanophase separation within the membrane matrix. The incorporation of f-CNDs improved water uptake, proton conductivity, ion exchange capacity (IEC), and oxidative stability compared to pristine and EFN-crosslinked membranes. Among the tested samples, the M1/EFN-0.1/CND-0.9 membrane exhibited the best electrochemical performance, achieving a proton conductivity of 0.14 S cm-1, an IEC of 1.21 meq g-1, and a peak power density of 0.21 W cm-2 with a cell voltage of 0.54 V at a current density of 0.40 A cm-2. Furthermore, M3 based composite membranes demonstrated superior thermal, mechanical and oxidative stability, confirming the reinforcing and stabilizing role of f-CNDs. Overall, the synergistic effect of EFN crosslinking and f-CNDs incorporation significantly enhanced proton transport, mechanical integrity, and durability, establishing these nanocomposite membranes as promising candidates for next-generation PEMFC systems.
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