Fluorine-Free Gas Diffusion Media for Polymer Electrolyte Fuel Cells Part I: Silicone-based Microporous Layers
Year: 2026
Type: preprint
Abstract: The widespread use of fluoropolymers in electrochemical energy systems, coupled with increasing environmental, health, and regulatory concerns surrounding per- and polyfluoroalkyl substances (PFAS), is motivating the development of fluorine-free alternatives. Here, silicone-based resins are evaluated as fluorine-free binders for microporous layers (MPLs) and integrated into fully fluorine-free gas diffusion media (GDMs). Using Sylgard 184 silicone elastomer, the binder content was systematically varied, identifying 25 wt.% as the lowest loading that provided sufficient water repellency. At this loading, the influence of binder chemistry was investigated by replacing Sylgard 184 with KR-220L, a methyl silicone rigid resin. Although the resin chemistry strongly affected MPL thickness, porosity, and crack formation, its impact on fuel-cell performance was limited. Fully fluorinefree GDMs were then fabricated by depositing silicone-based MPLs onto carbon fiber substrates hydrophobized via organosilicon electrografting. Replacing a commercial PTFEtreated substrate with the fluorine-free electrografted substrate resulted in only a minor decrease in current density, from 4.2 to 4.0 A cm-2 at 0.3 V under high-humidity conditions; both exceeded the commercial fluorinated reference (3.8 A cm-2). Accelerated stress testing further demonstrated promising durability. Overall, silicone-based materials represent a viable route toward replacing fluorinated components in GDMs.
Source: ChemRxiv
Institution: Eindhoven University of Technology
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204824989