Hydrogen Fuel Cells, Deionised Water and PTFE

The future of energy is hydrogen

Hydrogen is an element that exists naturally in the air. Most people also know that water is made up of hydrogen and oxygen. As a fuel, hydrogen is as clean as it gets. When hydrogen is used in a fuel cell, the only waste product is water.

Whilst hydrogen exists in the atmosphere, the amount of it required to fuel vehicles means hydrogen must be produced, stored and delivered on an industrial scale. Hydrogen can be produced in a variety of ways, and the cleanest and least energy-impactful method is via High-Pressure Electrolysis.

High Pressure Electrolysis (HPE)

Electrolysis is a process which uses an anode and a cathode separated by an electrolyte. This basically works as the reverse process to a fuel cell, which takes hydrogen and turns it into water; electrolysis takes water and turns it into hydrogen.

• The process uses an electrolyser which consists of an anode and a cathode separated by an electrolyte (in this case, deionised water).
• Water reacts at the anode, splitting the water molecules to form oxygen and positively charged hydrogen ions (protons).
• The electrons flow through an external circuit and the hydrogen ions selectively move across to the cathode.
• At the cathode, hydrogen ions combine with electrons from the external circuit to form hydrogen gas.

There is more than one way to produce hydrogen using an electrolysis process, but deionised water is considered the cleanest way to create hydrogen fuel cells for renewable electricity.

One of the issues around using HPE for industrial applications (like renewable fuel) concerns the storage, handling and delivery of deionised water. Storing deionised water in metal equipment can cause problems. Deionised water, as the name suggests, is simply water with the ions removed. Because the water is pure, the natural process is for it to then attract ions from other materials – which in the case of metallics, causes them to dissolve, or rust. As an aside, this is very interesting because, while this water will corrode steel or aluminium, it’s still perfectly safe to your skin and you could drink it safely- though it wouldn’t taste very good!

Having said that, we'll leave the problem of taste to the other experts. Our skills are much better suited to solve the metal corrosion issue during production and storage. 

How can we store deionised water in metal?

To stop the natural rust process when storing and processing deionised water in metal, the metal must first be protected with an anti-corrosion coating. The most effective rust protection comes in the form of an anti-corrosion protective Fluoropolymer Coating, such as PTFE or Halar. If deionised water comes into contact with a Fluoropolymer – nothing would happen; if it comes into contact with metal – it would corrode the metal.

This is one of the many areas where AFT are working extensively in next-generation renewables. Storage and delivery components and equipment that are typically manufactured from steel or aluminium can be coated in PTFE or Halar and as such deliver the same brilliant neutral, inert atmosphere to carry deionised water with the structural strength of traditional metal vessels and pipework. 

PTFE and Halar are also ideal for bespoke fittings for machinery where deionised water comes into contact with metallics. Parts can either be coated to provide rust protection, or the parts themselves can be machined from PTFE or Halar to produce long-lasting components that are unaffected by the corrosion effects of the deionised water. 

This is yet another application for Fluoropolymer manufacturing and coatings where the fascinating inert and chemically-resistant properties of these materials can be delivered by AFT Fluorotec as a solution for handling critical material in the development and production of clean energy.