Possible Materrial Choices for Gas Diffusion Layers

What materials can be used for Gas Diffusion Layers?

A gas dif­fu­sion lay­er (GDL) is a crit­i­cal com­po­nent of an elec­trolyz­er or fuel cell, as it serves as the inter­face between the elec­trode and the gas that is being split. Although CAPLINQ does­n’t sup­ply all the pos­si­ble mate­ri­als that can be used, we find it impor­tant that our cus­tomers are aware of all the pos­si­ble options. 

GDLs are typ­i­cal­ly made from porous mate­ri­als to increase the sur­face area, trans­port water more effi­cient­ly, and to pro­vide more effi­cient gas trans­port which allows elec­tro­chem­i­cal reac­tions to take place. The GDLs are sand­wiched between the elec­trode and the mem­brane in the fuel cell, with one GDL on the anode (neg­a­tive) side and one on the cath­ode (pos­i­tive) side.

There are sev­er­al dif­fer­ent types of mate­ri­als that can be used as GDLs in elec­trolyz­ers, each with its own unique prop­er­ties and advan­tages. Some of the options for GDLs in elec­trolyz­ers include:

  • Car­bon Cloth or Acti­vat­ed Car­bon Fab­ric: These mate­ri­als are made of inter­con­nect­ed car­bon fibers and as such are con­duc­tive. It is a good choice for PEM (pro­ton exchange mem­brane) elec­trolyz­ers because it has good gas per­me­abil­i­ty and elec­tri­cal conductivity.
  • Graphi­tized Car­bon paper or pan­els are used as a gas dif­fu­sion lay­er (GDL) in PEM elec­trolyz­ers by sand­wich­ing it between the elec­trodes and the mem­brane. It is com­posed of thin sheets of car­bon fibers, which are often coat­ed with a thin lay­er of car­bon black or graphite to enhance its conductivity.
  • Met­al mesh or met­al foam: These types of mate­ri­als are made from met­als such as stain­less steel or tita­ni­um, and are used in alka­line elec­trolyz­ers. They have high elec­tri­cal con­duc­tiv­i­ty, good mechan­i­cal strength, and can with­stand high tem­per­a­tures and pressures.
  • Ceram­ic mate­ri­als: Ceram­ic mate­ri­als such as sil­i­con car­bide (SiC) can be used as GDLs in high-tem­per­a­ture elec­trolyz­ers, as they can with­stand high tem­per­a­tures and have good mechan­i­cal and chem­i­cal stability.
  • Ceram­ic-coat­ed mate­ri­als: Some man­u­fac­tur­ers use ceram­ic-coat­ed met­al mesh, or met­al foam, to enhance the GDL’s prop­er­ties, such as dura­bil­i­ty and chem­i­cal resistance.
  • Poly­te­tra­flu­o­roeth­yl­ene (PTFE): This hydropho­bic mate­r­i­al, also known as Teflon, is often used as a coat­ing on the sur­face of GDLs to pre­vent liq­uid water from pen­e­trat­ing the pores.
  • Poly­ben­z­im­i­da­zole (PBI): PBI is a high-tem­per­a­ture poly­mer that has good chem­i­cal and ther­mal sta­bil­i­ty, it is also hydropho­bic, that can be used as a sub­strate for GDLs.
  • Polyamide: Polyamide is also hydropho­bic, it can be used as a sub­strate for GDLs, it is also very strong and has good mechan­i­cal strength.
  • Cat­a­lysts: Some GDLs may also con­tain cat­a­lysts, such as plat­inum, to pro­mote the elec­tro­chem­i­cal reac­tions that take place in the fuel cell.
  • Graphene-based mate­ri­als: Graphene is a 2D mate­r­i­al that has a high sur­face area and high elec­tri­cal con­duc­tiv­i­ty, it can also be used as a sub­strate for GDLs, also it has good chem­i­cal and ther­mal stability.

It’s worth not­ing that the choice of GDL mate­r­i­al will depend on the spe­cif­ic appli­ca­tion and require­ments of either the elec­trolyz­er or the fuel cell.

Choice of GDLs on the anode side of an Electrolyzer or Fuel Cell

Gas dif­fu­sion lay­ers (GDLs) are used on both the anode and cath­ode sides of a fuel cell, but the mate­ri­als used may be dif­fer­ent depend­ing on the spe­cif­ic require­ments of the cath­ode side.

The anode side of a fuel cell or elec­trolyz­er is also called the anode com­part­ment or the anode cham­ber. It is where the oxi­da­tion process occurs, elec­trons are released from the fuel and then trans­port­ed through an exter­nal cir­cuit to the cath­ode side, gen­er­at­ing elec­tric­i­ty. The anode side is in con­tact with the fuel (usu­al­ly hydro­gen) and it’s where the fuel is oxi­dized, releas­ing elec­trons that will be used to gen­er­ate electricity.

Typ­i­cal­ly, met­als such as nick­el or sin­tered tita­ni­um are the mate­ri­als of choice on the anode side of the elec­trol­y­sis process because they have good elec­tron­ic and ion­ic con­duc­tiv­i­ty. They also have good cor­ro­sion resis­tance prop­er­ties and can with­stand high pressures.

Though car­bon paper can be used on the anode side of an elec­trolyz­er, it’s not the ide­al mate­r­i­al. Car­bon paper has high elec­tron­ic con­duc­tiv­i­ty, mean­ing that it can eas­i­ly con­duct elec­trons. How­ev­er, it has low ion­ic con­duc­tiv­i­ty, mean­ing that it does not con­duct hydro­gen ions very well. This cre­ates an imbal­ance in the flow of elec­trons and ions, lead­ing to an inef­fi­cient elec­trol­y­sis process. Addi­tion­al­ly, car­bon paper is not durable enough to with­stand the high pres­sures and cor­ro­sive envi­ron­ments that are often present in electrolyzers.

Choice of GDLs on the cathode side of an Electrolyzer or Fuel Cell

The cath­ode side of a fuel cell is also called a cur­rent col­lec­tor because it is respon­si­ble for col­lect­ing and trans­port­ing the elec­trons that are gen­er­at­ed on the anode side and then used to gen­er­ate elec­tric­i­ty. The cur­rent col­lec­tor helps to dis­trib­ute the elec­trons even­ly across the cath­ode sur­face, and also helps to main­tain the elec­tri­cal con­tact between the cath­ode and the exter­nal cir­cuit. This way, the elec­trons can flow through the exter­nal cir­cuit and gen­er­ate electricity.

The cath­ode side of an elec­trolyz­er is gen­er­al­ly con­sid­ered to be less cor­ro­sive than the anode side. The cath­ode side of an elec­trolyz­er is where oxy­gen is pro­duced, and oxy­gen is less cor­ro­sive than hydro­gen. Hydro­gen is gen­er­at­ed at the anode side and it is a much more reac­tive gas than oxygen.

On the anode side, there­fore, the same sin­tered tita­ni­um or nick­el can also be used, but because the envi­ron­ment is less cor­ro­sive, car­bon-based prod­ucts are pre­ferred because they are less expen­sive, more reli­able, and pro­vide sig­nif­i­cant­ly more com­press­ibil­i­ty improv­ing efficiency.

CAPLINQ is an inno­v­a­tive man­u­fac­tur­er and devel­op­er of key com­po­nents for elec­trolyz­ers and fuel cells includ­ing our car­bon-based products:

as well as our part­ners’ poly­mer-based solutions:

Please vis­it our web­site and feel free to con­tact us if you have any ques­tions about any of the prod­ucts we offer.

About Chris Perabo

Chris is an energetic and enthusiastic engineer and entrepreneur. He is always interested in taking highly technical subjects and distilling these to their essence so that even the layman can understand. He loves to get into the technical details of an issue and then understand how it can be useful for specific customers and applications. Chris is currently the Director of Business Development at CAPLINQ.

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