carbon paper manufacturing

How are carbon papers made?

Graphi­tized car­bon papers as gas dif­fu­sion lay­ers are a pop­u­lar solu­tion for fuel cell and elec­trolyz­er appli­ca­tions since they can be man­u­fac­tured at high vol­umes (scal­a­bil­i­ty) and low thicknesses. 

The main man­u­fac­tur­ing steps are: 

  • Chop­ping fibers + Paper wet laying
  • Resin impreg­na­tion + Graphitization
  • MPL + PTFE treat­ment (if applicable)

1. Chopped car­bon fibers are processed to a pri­ma­ry car­bon fiber web using a paper­mak­ing (wet-lay­ing) tech­nol­o­gy and sub­se­quent thermo-bonding. 

2. The raw paper is then impreg­nat­ed with car­boniz­able resins (car­boniz­able resins with the option­al addi­tion of car­bon fillers), cured, and recarbonized/ graphi­tized. This pro­ce­dure serves to adjust the poros­i­ty and enhance elec­tric and ther­mal conductivity. 

3. Dif­fer­ent GDL back­ings with dif­fer­ent filler con­tent could be the base for the final fin­ish­ing process­es, such as: 

  • Hydropho­bic treat­ment with PTFE 
  • Coat­ing with a micro­p­orous lay­er (MPL)
  • Sin­ter­ing (ther­mal anneal­ing) to bond the substrate/MPL

Sim­ple Car­bon plate process goes through the fol­low­ing steps

Dis­per­sion > Resin impreg­na­tion > Mold­ing > Car­boniza­tion > Graphitization

These thick­er prod­ucts have high­er ther­mal con­duc­tiv­i­ty, high dura­bil­i­ty, low car­bon cor­ro­sion and are typ­i­cal­ly used for Elec­trolyz­ers and dis­trib­uted pow­er gen­er­a­tors. They are also known as Mold­ed graphite papers or Car­bon plates.

Advan­tages of paper­mak­ing approach for car­bon papers

A car­bon paper with MPL treat­ment will tra­di­tion­al­ly go through the fol­low­ing man­u­fac­tur­ing steps:

  1. Dis­per­sion
  2. Resin impreg­na­tion
  3. Low tem­per­a­ture carbonization
  4. High tem­per­a­ture graphitization
  5. Micro­p­orous Lay­er coating
  6. Resing impreg­na­tion
  7. Heat treat­ment (1600 or 2000°C)

These thin­ner car­bon papers that usu­al­ly (but not nec­es­sar­i­ly) come with an MPL coat­ing are typ­i­cal­ly used for Fuel cells. These fuel cells are used in vehi­cles, fork­lifts, drones and res­i­den­tial appli­ca­tions. These vehi­cles tend to need high­er pow­er stacks with robust prop­er­ties in thin assem­blies with high gas per­me­abil­i­ty and porosity. 

What is a PTFE treatment?

PTFE treat­ments on car­bon papers are used to make them hydropho­bic. Wet­ta­bil­i­ty affects water man­age­ment and ulti­mate­ly the over­all cell per­for­mance. A hydropho­bic agent such as PTFE or flu­o­ri­nat­ed eth­yl­ene propy­lene (FEP) could help to cre­ate a hydropho­bic GDL, required in PEMFCs.


  • Removal of excess water
  • Suit­able for wet oper­at­ing con­di­tions at high rel­a­tive humid­i­ty and low oper­at­ing temperature


  • Poros­i­ty is reduced
  • Change in pore size distribution
  • Decreased air permeability
  • Increase in ther­mal and elec­tri­cal resistance

What is a Microporous layer?

To improve the water man­age­ment in GDLs, a hydropho­bic MPL (micro porous lay­er) is com­mon­ly applied to the GDL side next to the CL (cat­a­lyst lat­er). MPL is com­mon­ly devel­oped using car­bon black and PTFE.

This overview should give you a good under­stand­ing of all the process steps that are nec­es­sary to man­u­fac­ture a car­bon paper with PTFE and a micro­p­orous lay­er such as LINQCELL GDP210-MPS. Oth­er than the process com­plex­i­ty we want to focus on the mul­ti­ple oven steps and the ener­gy inten­si­ty of this process. This ener­gy inten­si­ty is a huge part of the man­u­fac­tur­ing cost and that’s why we want to opti­mize it for the max­i­mum pro­duc­tion yield with the min­i­mum ener­gy cost. For more details read this arti­cle where we dis­cuss how we can col­lab­o­rate to opti­mize your process and our man­u­fac­tur­ing to reduce the total BOM cost of fuel cells and electrolyzers.

Con­tact us for more infor­ma­tion and for a call with our prod­uct experts that can help you ini­ti­ate or opti­mize your project.

About George Kountardas

George is a Jack of all trades with an unappeasable inquiring mind. Obsessed with new products and technologies, he is always pushing forward for better, faster and more efficient applications. Always learning something new.

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