Waterguide - Electrolysis types
Ultrapure water is the central raw material in electrolysis. Scalable frame and container plants produce ultrapure water for the electrolyser. Four different electrolysis technologies can be distinguished in this context:
- AEL electrolysis: In alkaline electrolysis (AEL), deionised water is used and mixed with potassium hydroxide in the further course of the process. Under DC voltage, gaseous hydrogen is formed at the cathode in the electrolysis cell, which is separated by a permeable membrane. The advantages of the process are the cost-effective use of materials and high long term stability.
- PEM electrolysis: Instead of a liquid electrolyte, this process uses a gas-tight proton exchange membrane (PEM) made of polymer. Positively charged hydrogen ions move through the semipermeable exchange membrane to the cathode side. Gaseous hydrogen is then produced here as well. The process scores with a high power density, but requires the use of expensive precious metals such as iridium.
- AEM electrolysis: The anion exchange membrane (AEM) process combines the advantages of alkaline with PEM electrolysis. Since operation takes place under slightly alkaline conditions, inexpensive, non-precious metal catalysts can be used for the electrodes.
- SOEC electrolysis: Compared to the established electrolysis processes, solid oxide electrolyser cell (SOEC) technology promises high efficiency and great energy-saving potential. In this high-temperature technology, which is still in the testing phase, steam is split into pure hydrogen and oxygen ions. A solid oxide is used to separate the electrolysis cell.