Alkaline, PEM and SOEC Electrolyzers

Pure Hydrogen generation

PEM Electrolyzers

Current Collectors for PEM Electrolyzers

Using Carbon Paper & Panels as Cathode-side Current Collectors

LINQCELL GDL1500  are optimum for use as Cathode (Hydrogen Side) Current Collectors in PEM Electrolyzers. Unlike the standard thin/low density Gas Diffusion Layers (GDL) that are intended mainly for PEM and PAFC fuel cells, the Spectracarb Porous Graphite Engineered Panel Family has been specifically engineered for the special requirements of PEM electrolyzers. Features include thicker structures of from 1.5 to over 4 millimeters, and densities up to 0.95 g/cm3. These panels also have controlled compressibility to support the external forces from the assembly. In additional to several standard grades, these engineered panels can be made on a laboratory, prototype or production scale to meet specific customer requirements.


Graphitized Carbon Paper & Panels for PEM Electrolyzers


Graphitized Carbon Panels and Sheets

Figure 1. Various gas diffusion options plotted thickness in microns against density in g/cc. Spectracarb electrolyzer cathode carbon paper in the top right offer the industry's thickest panels with density ranges from 0.5g/cc to 1 g/cc. Carbon Papers, GDL felts and GDL cloths are all very thin - all of them are less than 500 microns thick and have densities between 0.2 g/cc and 0.6 g/cc.
Figure 2. Spectracarb carbon paper and carbon panels. The Spectracarb family of panels are specially constructed to meet specific customer specifications. Also, Spectracarb panels are available in several standard grades from 1.5 mm to 3.5 mm thickness and up to 0.95 g/cm3. Sizes up to 55 x 55 cm panels or machined discs can be supplied. We have succesfully been able to water-cut disks to a very tighht tolerance.

Spectracarb 2050A-12580 (Customer Specific Product)

Strain vs. Stress of carbon panel over compressive loading

Figure 3. Notice that the strain % is the same after repeated stress encounters, so there is no hysterisis.

Resistivity vs Stress of Graphitized Carbon Sheets

Figure 4. The resitivity of the carbon graphitized panels in milliohm-cm vs stress in psi. Notice the Spectracarb resistivity is the same after the initial loading as after the second loading.

Current Collector Stress: Repeated Stress <20% Strain

Figure 5. Whether the stress on the carbon paper is 500 psi or the stress on the carbon paper is 1000 psi, the strain is less than 20%.

Current Collector Resistivity: Repeated Stress <20% Strain

Figure 6. After repeated stress the resistivity in mohm-cm is consistent and with the same less than 20% strain.
Spectracarb GDL 2050A-6060
Property Units Value
Size mm 400 x 400
Thickness mm 1.5
Basis Weight g/m2 88
Geometric Density g/cm3 0.6
Average Pore Size microns 20
Electrical Resistivity
through-plane  in-plane


Thermal Conductivity
through-plane (@ 25°C)
through-plane (@ 100°C)
in-plane (@ 25°C)
in-plane (@ 100°C)


Tensile Strength


Flexural Strength MPa 37
Flexural Stiffness GPa 9.5
Compressive Strength MPa 2.1

Applications of Spectracarb Carbon Panels

Figure 7. Clockwise from left: PEM Electrolyzers, PEM Electrolyzer stack, Electrolyzers for military and self-containing applications (in this case, the O2 is produced to provide breathable air), China Bus program used Spectracarb carbon paper for fuel cells.

GDLs can be used in a variety of Technical Engineering Applications such as

  • PEM Electrolyzers
  • Fuel Cells
  • Heat Management
  • Redox Flow Batteries
  • Gas Diffusion Layers
  • Gas Diffusion Media
  • Porous Graphitized Carbon Sheets
  • Fuel Cell Powered City Buses


  • Lower Cost compared to Titanium Mesh / Sintered Ti for Cathode (H2 Side) Electrode Thicker Plates (Up to 5mm)
  • Higher Density (up to 1 g/cc)
  • Higher Bending Stiffness vs Stacking of Thin Papers
  • High Elastic Spring Compression Constant (up to 30% compression with full recovery)
  • Good Machinability
  • Hybrid Constructions Possible
  • Long Term Performance / Corrosion Resistance
  • Demonstrated: Commercial / Military Applications
  • Laboratory/ Prototype and Commercial Scale

 Spectracarb porous graphite current collectors for PEM electrolyzer application.