One of the key components in electrolysis stacks for hydrogen production - 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 its complex extraction and processing. Researchers at Fraunhofer UMSICHT and Ruhr University Bochum have now discovered that Carbon-based bipolar plates have the potential to replace titanium bipolar plates in the electrolysis stack.
Bipolar plate made from thermoplastic polymer-bonded carbon matrix
The new carbon-based bipolar plate, developed and patented by Fraunhofer UMSICHT, consists of a thermoplastic polymer-bonded carbon matrix with conductive additives such as carbon black and graphite. It is produced in a powder-to-roll process. The material and production process enable the continuous manufacture of a bipolar plate that is both easy to process and weldable. It is already being used commercially in the field of redox flow batteries.
Endurance test passed
The researchers 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. In this way, they evaluated the suitability for real applications and the choice of parameters. In the in-situ tests, the bipolar plates were subjected to accelerated ageing tests with varying current densities between 1 and 3 A cm-2 for over 500 hours.
A cost-effective alternative
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.