Fraunhofer UMSICHT: Corrosion-resistant carbon-based bipolar plates

Proton exchange membrane electrolysis is considered the most promising way of producing green hydrogen. However, it is currently still not very economical because one of its key components - the bipolar plate - is usually made of titanium. The metal impresses with its corrosion resistance during electrolysis, but is more expensive than other metals due to the complex extraction and processing involved. Researchers at the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT and Ruhr University Bochum have discovered that carbon-based bipolar plates can be a more cost-efficient and scalable alternative. Their investigations focused on a new carbon-based bipolar plate - developed and patented by Fraunhofer UMSICHT. It consists of a thermoplastic polymer-bound carbon matrix with conductive additives such as carbon black and graphite and is coated in a powder-to-roll process. The material and production process enable the continuous production of a bipolar plate that is both easy to process and weldable and is already being used commercially in the field of redox flow batteries.

The researchers have subjected this bipolar plate and a bipolar plate made of titanium to comprehensive ex-situ and in-situ tests. In the ex-situ tests, they carried out electrochemical corrosion studies, then analyzed the corrosion in scanning electron microscope images and measured the weight loss of the carbon-based bipolar plate to assess its suitability for real applications and the choice of parameters. In the in-situ tests, the bipolar plates were subjected to accelerated aging tests with varying current densities between 1 and 3 A cm-2 for over 500 hours. The researchers found that the carbon-based bipolar plate has an ageing rate in the low µV h-1 range and thus shows promising performance. This means that it can certainly compete with titanium bipolar plates and represents a much more cost-effective alternative. Another advantage: due to its material properties such as weldability, it enables completely new designs for PEM electrolyzers. The potential to replace titanium bipolar plates in the PEM electrolysis stack and make electrolysis scalable at the same time is therefore definitely there. The task now is to investigate the new material further and, if necessary, to optimize it in order to further reduce the costs of electrolysis and thus make the production of green hydrogen more economical.