Last week, SGL Group announced that it will provide its SIGRACET® brand of wet-laid nonwoven CFRP gas diffusion layers (GDLs) for the fuel cell of Hyundai’s NEXO hydrogen fuel cell vehicle.

Fuel cell technologies are considered one of the most environmentally friendly future solutions in energy. The only waste product following the reaction is water, H2O, which can be discharged in the form of steam. After leading the way with its iX35 fuel-call car in 2012, now Hyundai has optimized its hydrogen-powered drive with its NEXO model, a zero-emissions vehicle. Serial product began last month.

“We are excited to extend our partnership with Hyundai – our years of developmental work is now paying off,” said Dr. Tilo Hauke, Head of Central Innovation at SGL Group. “For us, this is also a major step in shaping the key technology topics of our time, including mobility and new energies.”

As SGL explained in a white paper, gas diffusion layers are crucial components for proton exchange membrane fuel cells (PEMFCs) since they modulate all relevant transport processes – the fuel, reaction products, electricity and heat. A PEMFC typically consists of two flow fields, two gas diffusion layers, catalyst layers and the proton exchange membrane (PEM)

The GDLs act as an interface between the flow field (structural cell parts with millimeter-size features) and the electrocatalysts (reaction layers with nanometer-size features), directing the fuel to the active sites while removing heat and reaction products and electrically wiring the reaction layers with the current collectors.

GDLs typically have a bilayer structure consisting of a macro-porous wet-laid carbon backing and a micro-porous carbon layer (MPL). The fibrous backing material governs its mechanical properties – compression behavior, bending and shear strength. The backing also impacts on the thermal and electric parameters.

Its hydrophobic properties and its microstructure have a significant effect on the water management via the capillary pressure-saturation relationship. Micro-porous layers are additional mediators of the water management of PEMFCs where pore size distribution, the type of carbon fiber and polytetrafluoroethylene (PTFE) load can be adjusted to optimize water management under the prevalent operating conditions.

Additionally, the MPL facilitates catalysts deposition and effectively protects the proton exchange membrane against perforation by the carbon fiber.

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