Gaskets for use in hydrogen electrolysis

When producing carbon-free hydrogen from renewable sources, electrolysis is an excellent choice. The process of electrolysis takes place in something called an electrolyser, which can range in size from small appliance-size equipment to larger scale production. So, what is hydrogen electrolysis? Continue reading our guide to discover more about hydrogen production of electrolysis.

What are electrolysers?

Electrolysers are pieces of equipment that can use renewable electricity to produce high purity chemicals. These chemicals can be sold as reagents or substances for industry, or can be stored for future use. The stored chemicals – typically hydrogen – can be fed into a fuel cell to generate electricity. Electrolysers produce high purity gas by breaking down reactants with electricity. This is known as electrolysis.

Electrolysers are most commonly used with renewable energy because they’re able to work with a fluctuating power supplies, such as wind, solar and tidal power.

One method of operation is to use these renewable energy sources to generate high purity hydrogen, which can be stored for use with a fuel cell.

Types of electrolysers

A key component of renewable energy systems that use hydrogen are electrolysers. There are two types of commercial electrolysers for hydrogen production of electrolysis, and they are:

• Proton Exchange Membrane (PEM) – Produces high current densities and high voltage efficiency. This type of electrolyser is compact, produces high gas purities and responds well to dynamic electrical inputs, such as those from renewable sources. The disadvantage is that this piece of equipment comes with high-cost components from use of rare metals.

• Alkaline – With a conversion efficiency of over 95%, these are the most commonly used electrolysers for hydrogen production. One huge benefit of this type of equipment is that it has cheap electrode and catalyst materials. However, one disadvantage is that they have difficulty responding to fluctuating electrical input, such as those provided by renewable energy, which can lead to a loss of efficiency.

How do electrolyser gaskets work?

Alkaline operation:

1. Water is reduced at the cathode to produce hydrogen and hydroxyl ions by electrolysis
2. OH passes through the electrolyte (green) under the influence of the cathodes electrical field
3. On reaching the anode hydroxyl, ions gives up electrons to form oxygen and water
4. Hydrogen gas purities are around 99.8%; downstream processing can increase this to 99.998% 

Proton Exchange Membrane operation:

1. Water is oxidised at the anode to produce hydrogen ions and oxygen gas
2. Hydrogen ions pass through the electrolyte under the influence of the electrical field
3. When the hydrogen ions reach the cathode they gain an electron and form hydrogen gas

Hydrogen electrolysis gaskets

At TRP Polymer, we have manufactured electrolyser gaskets for the chlorine and hypochlorite (chloro-alkali electrolyser) industry for over 30 years. During this time, we’ve developed and specialised in bonding rubber to a thin PTFE veneer.

Over the past 30 years, we have made several advancements within the industry.

Firstly, an EPDM capable of excellent performance over 150°C was developed which now has many years of successful commercial use. This EPDM has excellent chemical resistance and high temperature resistance. 

Secondly, the ability to process chemically-resistant PTFE veneers has been continuously developed to a point where veneers as thin as 0.25mm can be used for larger gaskets.

Thirdly, TRP Polymer’s expertise in chemically bonding PTFE and elastomers have significantly reduced permeation in applications. Research into TRP’s gasket has shown that for some chemicals, permeation can be reduced by up to 100 times compared to standard elastomers. The physical and mechanical properties are also maintained over longer periods of time.

The experience that TRP has in the field of hydrogen electrolysis gaskets has led to them being used in some of the biggest electrolysers. As a result, mouldings of up to 2.5 x 2m are currently produced at TRP, where a tolerance of +/- 5.5mm is maintained.

New developments of gaskets for use in hydrogen electrolysis

TRP Polymer has been involved in the manufacture of gaskets for use within hydrogen production of electrolysis, and in the manufacture for use within hydrogen fuel cells. This has led to the testing of our own materials in 99.995% H2 at 80°C (the approximate operating temperature of a fuel cell). The results can be seen below:

The materials are designed to serve a variety of applications:

• Butyl serves high-pressure hydrogen storage where loss of hydrogen by permeation is to be kept to a minimum (TRP compound reference: D167).
  
• FKM has excellent chemical resistance to a wide range of media and has been used by TRP in a variety of electrolysis cells ranging from small, lightweight and portable equipment to large commercial electrolysis cells. We have developed two materials for these applications (F344 and F361).
• High chemical/temperature resistance EPDM can commonly be used with seals and gaskets, but TRP recommends applying a PTFE veneer.

• EPDM with PTFE veneer is specifically designed for a long service life use within electrolysis gaskets. Gaskets manufactured by TRP, in this way, have a history of having a service life in excess of 10 years. The PTFE layer acts as a high-chemical resistance boundary, whereas the EPDM acts to form the seal and energise the PTFE. This technology enables longer service life than PTFE or EPDM, as the PTFE shields the EPDM chemically and thermally, and the EPDM eliminates common problems with PTFE gaskets, such as cost and creep. (E286 + PTFE)

In addition to the above developments of low permeation materials, TRP has also developed a reduced carbon footprint EPDM that’s suitable for use in electrolyser gaskets. Its chemical resistance and physical properties to be applied to a PTFE veneer match that of existing formulations. The new EPDM shows a carbon footprint reduction of 1kg of CO2 per 1kg of rubber when compared to EPDM produced solely from non-renewable hydrocarbons.

Contact TRP Polymer

If you would like to discuss the range of materials available at TRP Polymer, don’t hesitate to contact us on 01432 268899, or email us at sales@trp.co.uk.