The gas diffusion layer (GDL) – a key component of fuel cells

The sustainable generation and storage of energy is critical to reducing our greenhouse gas emissions and helping to mitigate climate change.

Arguments in favor of hydrogen...

...there are many. It allows “well to wheel”, i.e. CO2-neutral transport from production to the consumer. The filling station infrastructure only needs moderate upgrading. Filling the tank can be done in a few minutes, similar to a combustion engine, and provides enough fuel for up to 800 km.

The principle

At the heart of the fuel cell is the Catalyst Coated Membrane (CCM), a membrane on which catalysts are applied. This membrane separates hydrogen and oxygen and simultaneously transports the positively charged protons from the hydrogen side (anode) to the air side (cathode). At the cathode, these protons use catalysts to react with atmospheric oxygen to form water. This produces electrical energy, e.g. for drives.

The role of the GDL…

...is very important in this context. “The GDL must optimally distribute all gases to the CCM electrodes and remove water, heat and electricity”, explained Dr. Volker Banhardt. “The more homogenously the gases are distributed and the more evenly they flow across the entire cross-section, the more electricity is produced and the power density of the fuel cell increases.”

"The fuel cell produces electricity, while lithium-ion batteries store it. Both technologies complement each other perfectly.”

Dr. Volker Banhardt, Head of Sales & Marketing Fuel Cell Products, FPM, Weinheim/Germany

The GDL material

To fulfill all the transport requirements mentioned, a conductive carbon structure is impregnated and coated with specially developed materials. Binding fluoropolymers allow the liquid to roll off so that the nonwoven does not become saturated with water. Thanks to its flexibility, the FPM carbon fiber structure can be easily compressed during the production process without being damaged.

“As a result, Freudenberg’s GDL is a key component in simplifying production and increasing the performance and service life of the fuel cell”, commented Dr. Volker Banhardt.

In detail – what does the Freudenberg GDL do?

Management of all transport functions from the CCM to the bipolar plate: hydrogen to the CCM anode side, atmospheric oxygen to the CCM cathode. Water removal from the anode into the bipolar channel structure.
Heat removal: dissipation of the reaction heat.
Electrical transport: dissipation of the anode-side electrons. This is achieved by the appropriate use of highly conductive raw materials.
Mechanical tolerance compensation: all components exhibit tolerances, as does the GDL. However, this can deform locally and thus absorb tolerances of adjacent components.
Process reliability: the GDL is further processed in various steps. Due to its special carbon fiber base structure, it is robust and easy to roll.
Membrane protection: membranes used in fuel cells are very thin and at the same time exposed to high loads. The special surface of the Freudenberg GDL protects the membrane against unacceptable loads during operation.