Prevention of Frost-Driven Self-Fracture of Ionomer-Bound Carbon Films by Controlling Freezable Water Domain Size

Abstract

The frost-driven self-fracture of ionomer-bound carbon electrodes compromises the mechanical stability of electrochemical systems under subzero conditions. This study suggests that the mechanical degradation of ionomer-bound carbon electrodes under subfreezing conditions is primarily driven by damage within the ionomer binder phase rather than within the nanopores. This damage occurs owing to the expansion of confined water upon freezing. Reducing the size of the freezable water domains significantly enhances the mechanical robustness. Structural and mechanical analyses reveal that thermal reconfiguration effectively modifies the ionomer nanostructure, leading to an approximately 30% reduction in water uptake and improved resistance to frost-induced self-fracturing. Nanostructural analyses further confirm that crystallized packing in the ionomer binder minimizes the number of water retention sites, thereby restricting the buildup of internal stress during freezing. Consequently, the elongation of the as-prepared electrodes reduces by approximately 65% after freezing at −10°C, whereas that of the thermally reconfigured electrodes is above 90% of its initial value with minimal deterioration. These findings highlight the critical role of ionomer-phase engineering in improving the low-temperature durability of ionomer-bound carbon electrodes, providing a scalable strategy applicable to fuel cells, water electrolyzers, and next-generation energy storage systems without requiring antifreezing agents.

Keywords

carbon electrodes / frost-driven fractures / ionomer-bound carbon films / mechanical robustness / nanoporous structure / subfreezing durability

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