Speaker
Description
Polymeric diaphragms in alkaline water electrolyzers are designed for high chemical resilience under elevated temperatures and concentrated KOH environments. Although their bulk morphology remains stable, extended operation often results in progressive increases in ionic resistance, indicating degradation mechanisms beyond simple mass loss or porosity alteration. Empirical studies confirm that pore-size distribution and structural parameters such as tortuosity remain largely invariant [1], implicating surface physicochemical transformations—particularly wettability deterioration—as the dominant factor [1, 2]. These alterations hinder electrolyte infiltration, elevate ohmic losses, and intensify hydrogen crossover, thereby compromising both energy efficiency and operational safety [3]. Consequently, precise control of interfacial wettability emerges as a critical strategy for prolonging diaphragm service life and ensuring robust electrolyzer performance.
We propose that this resistance increase stems primarily from changes in surface chemistry and wettability. Specifically, redistribution of hydrophilic nanoparticles and localized surface erosion can increase contact angles [4], reduce electrolyte penetration and impair ionic transport. This uneven electrolyte saturation may create localized thermal gradients, leading to hot spots that accelerate mechanical and chemical degradation. These effects are consistent with studies highlighting the critical interplay between wettability, bubble dynamics, and current density in electrolysis systems.
To quantitatively evaluate this hypothesis, we implement a gas-liquid pore-network model on synthetic geometries reflecting actual separator volumetrics and pore-size characteristics. By simulating relative permeability on the synthetic geometries with altered surface features resembling the stages of an actual membrane’s transition from fresh (hydrophilic, with contact angles ~80°) to spent (hydrophilic, with contact angles ~95°), we assess the resultant impact on electrolyte distribution, resistance, and hydrogen crossover.
References:
1. H. In Lee, D.T.D., J. Kim, J. H. Pak, S. k. Kim, H. S. Cho, W. C. Cho and C. H. Kim, The synthesis of a Zirfon‐type porous separator with reduced gas crossover for alkaline electrolyzer. International Journal of Energy Research, 2019.
2. W. Song, Z.S., M. Guo, Y. Tang, M. Zhang, K. Su, J. Li and Z. Li, Novel high-safety composite separator: Achieving efficient alkaline water electrolysis by compositing microporous polysulfone membrane on one side of complete structure polyphenylene sulfide fabric. Chemical Engineering Journal, 2025. 503.
3. Dirk Henkensmeier, W.-C.C., Patric Jannasch, Jelena Stojadinovic, Qingfeng Li, David Aili, and Jens Oluf Jensen, Separators and Membranes for Advanced Alkaline Water Electrolysis. Chemical Reviews, 2024. 124 (10), 6393-6443.
4. H. Shin, S.-M.J., Y. J. Lim, O.-J. Yim, B.-J. Lee, K.-S. Kim, I.-H. Baek, J. Baek, J. Lee and Y.-T. Kim, Highly Efficient and Durable Ammonia Electrolysis Cell Using Zirfon Separator. Advanced Science, 2025. 12.
| Country | India |
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