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.
- Graphitized carbon paper & panels
- Carbon cloths and activated carbon fabrics &
- Electrically conductive plastics
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.