Validation and characterization of suitable materials for bipolar plates in PEM-WE

The polymer electrolyte membrane (PEM) electrolysis cell is a promising prospect for the production of clean hydrogen through the splitting of water with energy provided by renewable wind and solar sources. One component of the PEM electrolyzer is the bipolar plate (BPP), which serves as a multi-function component during PEM water electrolysis (WE). On one hand the BPP ensures the supply of water, and on the other hand it provides the electrical connectivity through the cell stack. Titanium is typically regarded as the state-of-the-art material used for the BPP. Mechanically it could potentially be replace by lower-cost materials such as stainless steel, but under the harsh environmental conditions present in PEM-WE, e.g. the high temperature, electrical potential and pH-value, stainless steel is not corrosion-resistant and metal ions can dissolve. In this case metal ions would poison the catalyst and membrane, which leads to a reduction in the cell performance [1]. The pH-value of oxygen enriched circulating water is the dominant mechanism influencing the development of corrosion within the cell. We have tested several coatings such as Au and TiN in PEM-WE environments of varying severity for the application as a protective layer of bipolar plates. In order to determine possible candidates for a long-term test under real simulated PEM-WE conditions, an experiment to determine pH-value in PEM-WE operation was developed to obtain the required pH-value for the ex-situ testing of various coating materials.Keywords: PEM water electrolysis, bipolar plates, characterization methods, pH value, real operating environment [1] Trappmann, C., Metallische Bipolarplatten für Direkt-Methanol-Brennstoffzellen / Christian Trappmann, 2010, Cuvillier: Göttingen. p. III, 200 S