Graphitized Carbon Papers

Graphitized Carbon Fiber Papers and Plates
Product	Thickness	Thickness (mm)	Density (g/cm³)	Basis weight (g/m²)	Through-Plane Resistance (mΩcm²)	Through-Plane Resistivity (mΩcm)	Voltage Loss (mV)
LINQCELL GDP 180	0.007"	0.18	-	50	7	-	-
LINQCELL GDP 210	0.008"	0.21	-	51	10	-	14
LINQCELL GDP 240	0.009"	0.24	-	90	15	-	-
LINQCELL GDP 340	0.013"	0.34	-	90	10	-	-
LINQCELL GDL 1500	0.059"	1.5	0.60	858	13.32	90.6	24.3
LINQCELL GDL 1500B	0.059"	1.5	0.60	670	21	140	39
LINQCELL GDL 1850	0.072"	1.85	0.85	1562	13.18	70.5	25.5
LINQCELL GDL 2200	0.086"	2.2	0.6	1550	17	110	35
LINQCELL GDL 2900	0.011"	2.9	0.60	1734	24.57	87.7	27.6

Frequently asked questions about Graphitized Carbon Fiber Panels

What is Carbon GDL Wet proofing?

A very common technique that is applied on Carbon GDLs is Wet proofing. Wet proofing the panels improves the water transport, increasing the total power generation. Additionally, wet proofing can stop GDLs from shedding carbon particles which helps with GDL handling.

Wet proofing Gas diffusion layers can be achieved by teflon dispersion or by applying hydrophobic treatments.

What is the GDL role in the assembly?

Gas diffusion layers structurally help the stack withstand the extension caused by the water absorbency. In addition to that, they aid with heat transfer, electrical surface conductivity, and the removal of excess water from the electrodes that is produced by redox reactions.

Finally, and most importantly, they clear the path for the Fuel and the Oxidizing agent towards the catalyst layers.

Can I just get an MPL treatment?

The carbon paper are not able to have a Microporous layer without PTFE. If you apply it on carbon paper without PTFE coating, the MPL will penetrate the back side of the carbon paper..

Do you have carbon papers in roll form?

Yes. Not every grade is flexible enough to be rolled without breaking or cracking but we do have sub-340um carbon papers that come in roll form. Higher than that it is usually difficult to roll without breaking so we can only provide standard 20 x 20cm, 40 x 40cm sheets, or custom dimensions if the quantities allow. Die cutting is also possible.

Do Carbon papers contain PFAS?

Since there are some talks about a PFAS ban in the European Union, starting from 2025, it is important to clarify where PFAS are present. Generally pure carbon paper doesn't contain any PFAS. Microporous layers and PTFE treatments are by nature susceptible to them. To outline:

- Carbon papers without any special treatments do not contain any PFAS
- Carbon papers with a Microporous layer contain PFAS
- Carbon papers with a PTFE treatment contain PFAS

Read our blog article that explains more about where PFASs are used in Graphitized Carbon Paper.

What's the most common thickness for Carbon Paper?

Generally, thin (<1mm) sheets are used for fuel cell GDLs, while thicker panels (1.5 - 3.0 mm) are used for electrolyzers. While CAPLINQ can custom-make specific thicknesses, these are what our customer most often ask us for.

Read our blog article that explains the most common thicknesses in GDLs for more info.

What type of binder resin is used for Carbon GDLs?

The binder resin component in the carbon paper papermaking process is Polyvinyl Alcohol; the binder in the carbon paper manufacturing process is Phenolic Resin. Both polyvinyl alcohol and phenolic resin do not contain PFAS

Additionally, after heat treatment in the manufacturing process, most of the resin is converted into carbon residue. Therefore, the main component of the finished carbon paper without MPL+PTFE is carbon.

Does CAPLINQ offer Spectracarb materials?

No. CAPLINQ no longer offers Spectracarb materials, but instead produces its own products under our LINQCELL brand name. Read here the history of CAPLINQ , Spectracarb, and LINQCELL.

Do you test radius, compression and thickness?

Radius is being tested with a standard PHOENIX tool. Compression is tested at 2 MPa. We conduct a single point stress test and also a 5 point (sides and center) compression test, to ensure that compression is evenly distributed.

Thickness measurements depend on the format. Rolls are being measured every 5 meters at a single point. Sheets are measured on a 5 point basis(center and four sides). The load is always mentioned in the specification sheet.

What is the difference between 1600 and 2000°C graphitization?

Other than being a bit more expensive, due to the much higher energy cost, the 2000°C graphitization can generally achieve better electrical properties. This can come to the expense of other properties like compressibility or brittleness. It is always a balancing act to understand and decide what best suits your application. Also highly graphitized papers are a bit grayer.

We are currently testing a large sheet, high graphitization oven so we will be happy to take any requests for carbon papers that need to be graphitized at those temperatures.

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Graphitized carbon fiber plate applications

Graphitized carbon fiber papers have multiple uses but their main applications are typically gas diffusion layers or the base for the anode and cathode assembly sides. These are popular products for electrolyzers, PEM and AEM fuel cells, electrochemical devices and other specialty applications.

When used as Fuel cell electrodes they have very high strength, high conductivity and high durability. The GDLs have good air permeability and moisture transport and can be used for lab scale prototypes to mass commercial scale manufacturing.

PAFC (Phosphoric acid fuel cell) are mostly used for stationary power, PEM and AEM fuel cells for transportation power and eletrolyzers, well, they are electrolyzers. GDLs have been successfully used for fuel cells utilisation in the Asian markets and have powered the transportation grid for the Olympics and the World Expo.

Carbon paper manufacturing process

There are multiple steps to ensure our Carbon Papers are meeting the expected application requirements.

Our technical expertise with materials development along with our established supply chain and engineering management is key to produce a consistent and high level graphitized carbon plate.

If quantity makes sense we are open to produce and provide alternative thicknesses and grades.

Microporous layers and PTFE

The main properties of Carbon GDLs containing PTFE and MPL are that they improve water transport and management.

Because water retention reduces power generation, GDL treated with PTFE (Teflon) can make the material hydrophobic and improve water transport. Furthermore, the GDL with MPL treatment helps to reduce contact resistance between the GDL and catalyst layer, limit catalyst loss to the GDL interior, and improve water management by providing effective water transport.

These changes will result in higher through plane resistance so the density might need to be lowered to compensate for this increase. As an added note, thicker plates will see lower water management results from these treatments. They are more effective for thinner papers or plates.

Testing Methods

Voltage Loss at 500mA/ cm² and 20N/ cm² is measured between a gold plated copper stamp and a gold plated base plate

Thickness measurements

Carbon papers as Gas diffusion layers (GDL)

Gas diffusion layers are mainly based on Carbon cloth, felt graphite or Carbon paper and they can be treated to acquire various properties. They ensure the uniform distribution of reactive gases on the surface of the electrodes, and they also aid the transport of electrons to or from the external electrical circuit.

As an electrode we combine them with a catalyst ink to create the electrodes that go on either side of the ion exchange membranes.

For example they can be used as Cathode current collectors for PEM electrolyzers.

PEM water electrolysis uses electricity to split water into hydrogen and oxygen. A typical PEM eletrolyzer operates between 60°C and 90°C under pressures between 1 and 20 bars. An important part of the assembly is the porous current collector.

Desired Properties of the collector are low Interfacial Contact Resistance, high electrical conductivity, structural stability and compressibility and finally Electrochemical corrosion and Hydrogen embrittlement resistance

Carbon Gas diffusion layers are used for what they really are. In a MEA5 we have the following order (see image above):