Spectracarb™ 2050A Gas Diffusion Layer (GDL) sheets are porous “graphitized” resin bonded carbon fiber papers and
multi-ply panels specifically designed for use in PEM, DMFC and PAFC fuel cells, Electrolyzers, Humidifiers and Other
Electrochemical Devices.
These products are optimized for the following
properties:
Electrical Conductivity
Mechanical Strength and Durability
Gas/Air Permeability
Water Management
Spectracarb GDLs are produced in the USA and are
available in a wide range of standard & custom
grades, densities, sizes and materials for fuel cells,
electrolyzers, humidifiers, specialty batteries and
other electrochemical applications.
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.
Main Functions:
Current conduction BiP to electrodes
Medium to transport H2O and O2
Mechanical Support of MEA
Required Property:
Low Interfacial Contact Resistance
High electrical conductivity
Good level of compressibility
High level of structural stability
Electrochemical corrosion resistance
Hydrogen embrittlement resistance
Traditionally, a sintered titanium plate has been used as the cathode current collectors. This technology is proven but has
a number of significant drawbacks. First and foremost, there is enormous pressure to significantly reduce the cost of the
PEM Electrolyzers. Sintered titanium is typically used in thicknesses of 1mm. Thicker layers could be desirable, but cost
has a linear relationship to thickness, so thicker materials are simply much more expensive. Graphitized carbon sheets do
not have such a linear cost-relationship.
AS
As important as cost is, PEM Electrolyzer components need to be structually sound, durable and reliable. In practice as a
current collector, this means that the collectors need to have resistance to electrochemical corrosion as well as resistance
to hydrogen embrittlement. While the sintered titanium is both structurally sound and has a good resistance to
electrochemical corrosion, over time and under pressure, the compressed hydrogen makes the titanium malleable,
reducing it’s long-term reliability.
A summary of the other differences between Spectracarb GDL 2050A-6060 Graphitized carbon sheets and sintered
titanium plates can be found in the following table.
Material Properties
Spectracarb 2050A-6060
Sintered Titanium
Thickness
Thickness range from 125micron to 4mm. Cost has
non-linear relationship.
Any thickness is possible, but cost has a
linear relationship to thickness
Oxidation on Cathode
(H2) side
No such effect with the Spectracarb GDL
Presents longer-term reliability as the
compressed H2 makes the sintered
titanium malleable
Compressibility
Can be compressed significantly. A 3mm thick sheet
can compress to 2mm under pressures of 6-8MPa
Not compressible (rigid) at electrolyzer
pressures
Compression Set
No compression set. Near perfect hysteris after
pressure is removed.
N/A – Not compressible
Pore Size
Random distribution, average pore size is 20 micron
20 – 100 microns
Porosity
70 – 75%
30 – 50%
Resistance Values
Slightly lower resistance values than with sintered
Slightly higher resistance values obtained
titanium. Higher hear treatment decreases resistance. than with carbon panels
Cost
Considerable price advantage of the carbon paper
Considerably more expensive. Twice as
expensive in low volumes.
Microporous Layer
Can be manufactured directly on the carbon paper
Requires a standalone MPL
Under Pressure
Carbon paper tends to become brittle under higher
pressure
No increased brittleness under pressure
Electrical Conductivity
Requires at least 100 S/cm, the higher the better
For more information on Spectracarb GDL 2050A or any other graphitized carbon sheet or paper, or to understand how you
can use them a current collectors in your PEM Electrolyzer application, please do not hesitate to contact us.
Rev. A April 2015
Americas
Engineered Fibers Technology, LLC
88 Long Hill Cross Road
Shelton, CT 06484
USA
Tel: +1 (203) 922.1810
Email: [email protected]
Europe, Middle East & Asia
CAPLINQ Europe BV
Provincialeweg 1
1561 KK Krommenie
The Netherlands
Tel: +31 (20) 893 2224
Email: [email protected]