ARCEO Engineering takes actively part in the hydrogen mobility revolution

Due to its experience in continuous PVD process acquired during the past 15 years, ARCEO Engineering is now at the heart of the PEMFC technology through the development of anti-corrosion and conductive coatings for metallic coils to produce bipolar plates designed for hydrogen fuel cells.

Fuel cells: How does it work?

In the context of green mobility, every original equipment manufacturer (OEM) in the automotive industry is currently looking into hydrogen-powered vehicles. Indeed, these vehicles, as they are propelled by a hydrogen fuel cell stack, are very clean vehicles with water as their only exhaust.

Fuel cells are electrochemical conversion devices that convert the chemical energy of hydrogen molecules (H2) into electrical energy and produce heat and water as the only by-products (green device). Several kinds of fuel cells exist (alkaline fuel cells, phosphoric acid fuel cells, solid oxide fuel cells, etc.) but the one which is used in the mobility industry is the proton exchange membrane fuel cells (PEMFCs). Figure 1 shows a scheme of a PEMFC stack and the decomposition into its components. Indeed, a PEMFC is in fact composed of an addition of small fuel cells, forming a fuel cell stack. Each cell (repeating unit) is constituted of a membrane electrode assembly (MEA) which is sandwiched by two bipolar plates (BPPs). The MEAs and the BPPs are the two major key components of the PEMFCs.

 

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Figure 1. The fuel cell stack and its components

The BPPs are usually thin metallic plates, separating each cell of the stack. They must resist to the pressure used to maintain all the cells together without undergoing too much deformation. They also must conduct the electrons to the external circuit. Moreover, they are stamped to form channels through which the gases go. The objective of these channel is to bring the gases everywhere at the surface of the gas diffusion layers. Finally, they usually have water flushing inside them to cool the fuel cell stack as the stack produces heat as a by-product.

 

Bipolar plates technical expectations

The BPPs must exhibit particular properties in order to perform well in fuel cell stacks. They must be strong enough to resist to deformation when pressed but, in the case of mobility, they also must be thin and light in order to reduce the weight of and the space needed for the fuel cell stack. Notwithstanding, the material used for the BPPs must be easily stamped to form the gas channels. Moreover, they must be conductive and especially have a very low interfacial contact resistance (ICR) with the gas diffusion layer, usually made of carbon fibers. This property is essential to obtain the most efficient fuel cell stack because it decreases the resistance of the cells allowing a better electron transportation, and so, a higher electricity production. Last but not least, the BPPs must resist to the highly corrosive medium of the fuel cell stack. Indeed, the BPPs are in contact with hydrogen, oxygen, protons (from the hydrogen oxidation) and water, i.e. with an aggressive acidic media, at relatively high potential and high temperature.

In a few words, the materials composing the BPPs must be stiff in a reasonable manner but adapted to stamping, very conductive with a very low ICR, and very resistant to corrosion.

ARCEO Engineering can produce coils answering these specifications. In opposition to the usual discontinuous PVD coating on already cut and stamped BPPs, these coated coils are ready to be cut and shaped to form the final BPPs to be easily integrated to any PEMFC systems.

 

The ARCEO Engineering PVD installation

The ARCEO Engineering Physical Vapor Deposition (PVD) installation is thoroughly described in this article from our website: http://www.arceo-eng.com/en/news/48_physical-vapor-deposition-pvd-technology.

In a few words, PVD is a coating technique belonging to the branch of vacuum coating technologies. Using PVD, it is possible to cover a surface with a solid material like aluminum, a metallic oxide such as titanium oxide (TiOx) or a ceramic material as titanium nitride (TiNx). This would not be feasible to achieve by roll coating due to material thermodynamic instability. The particularity of the ARCEO Engineering PVD installation (see Figure 2) is that the PVD is used continuously, producing coils of PVD-coated materials, instead of coated sheets/parts with the usual discontinuous PVD methods.

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Figure 2. ARCEO Engineering PVD line



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