Self-Standing Fluorine-Free Anode Microporous Layers Enabling Improved Hot and Dry Operation of Fully Hydrocarbon Proton-Exchange Membrane Fuel Cells

Abstract

Optimizing fuel cells for hot and dry conditions is crucial for heavy-duty vehicle applications. This study focuses on enhancing gas diffusion layers (GDLs) to improve water management and performance of hydrocarbon (HC) catalyst-coated membranes (CCMs). Thirty-micrometer thin, self-standing, and fluorine-free microporous layers (SS-MPLs) for fuel cell anodes using carbon black, graphite, and acrylic binder are developed. The impact of carbon black and binder quantities in SS-MPL compositions on morphology, surface wetting, permeability, electrical resistance, and electrochemical performance is investigated. The SS-MPLs demonstrate more homogeneous morphology and ≈10 times lower permeability compared to commercial references. Increasing carbon black in the SS-MPLs reduces permeability by a factor of ≈5. Contact angle measurements indicate a hydrophilic nature for all SS-MPLs, which is beneficial for water retention in hot and dry conditions. Optimal composition of 30% binder and 25% carbon black for the MPL, enabled a 41% higher current density (1243 mA cm⁻²) compared to the commercial anode GDL reference H14Cx653 (881 mA cm⁻²) at 0.65 V in 105 °C under 35 and 60% relative humidity at the anode and cathode. These results highlight the importance of GDLs in future membrane electrode assembly designs, particularly for HC-based CCMs, which are more sensitive to humidity.