“The aim of the project is to produce hydrogen using saltwater electrolysis in an environmentally friendly and cost-effective way – but with optimized efficiency and less use of chemical catalysts,” says Dr Mirjam Perner. She is Professor of Geomicrobiology at GEOMAR Helmholtz Centre for Ocean Research Kiel and is leading the project together with Prof. Dr Jana Schloesser, Professor of Materials Engineering at Kiel University of Applied Sciences, and Florian Gerdts, lead process engineer at the Kiel-based technology company Element22.
Up to now, electrolysis has required purified fresh water, as it contains neither salts nor minerals and therefore protects the electrolysis system from corrosion. However, only 2.5% of the world’s water reserves are freshwater. Furthermore, the desalination and purification of saltwater causes additional costs that could be avoided by utilizing seawater directly. As part of the SalYsAse project, the scientists want to utilize salt water directly from the sea. This presents them with a number of challenges. The salt it contains can produce toxic chlorine gas during the electrolysis of seawater. “Faster corrosion of the electrodes or undesirable side reactions can also occur. We want to prevent this by using suitable materials in combination with the microorganisms,” says materials expert Jana Schloesser.
In order to be able to utilize the seawater, the researchers want to use marine microbes in addition to conventional catalyst layers. The microbes come from the Baltic and North Sea, as they are best adapted to the conditions of salt water. Mirjam Perner explains: “The chemical element iridium is often used as a catalyst as it is very resistant to corrosion. However, it is rare and therefore only available in limited quantities. That’s why we want to use biocatalysts in the form of microbes.” The microbes should help to reduce or even circumvent the challenges posed by the use of salt water.
The project team is also using suitable materials for the membrane, which separates hydrogen and oxygen during electrolysis, and the porous transport layer. “The special feature of SalYsAse is that the porous transport layer not only conducts the current and the reaction media. We design it in such a way that this layer also acts as a carrier for the microbes. This means that biological catalysis takes place directly in the electrolysis cell – an exciting approach that brings together materials science and life sciences,” says Florian Gerdts. The project participants want to use porous titanium structures for this, as titanium is particularly resistant to corrosion, which is essential for use in seawater.
In future, the entire process is to take place where the electricity is already generated: at offshore wind turbines. In this way, the scientists avoid having to transport the electricity to the mainland first. This route is expensive and energy is lost. Instead, clean, climate-neutral hydrogen is produced on site. This can be transported onwards efficiently and used in energy-intensive industries such as steel and chemical production, for example.