Guest article by Alexander Knebel, press spokesman for the Zuse Community: Catalysis at the electrodes is a key factor of energy conversion in the fuel cell. Because valuable precious metals such as platinum are used as catalysts, increases in efficiency are of major interest for hydrogen drives.
At the DECHEMA-Forschungsinstitut (DECHEMA research institute), a member of the Zuse-Gemeinschaft (Zuse association), scientists, along with partners from science and industry, are improving polymer electrolyte fuel cells (PEMFCs) for the optimal use of platinum. The main goal: prevent the loss of power when using the precious metal during operation. This should work by distributing the precious metal as well as possible in the electrode structure while retaining the necessary stability. The researchers are not only working on the structure of the platinum on the electrodes, but also on the carbon substrate. “If the carbon is too smooth, the platinum particles tend to clump”, explains team leader Jean-Francois Drillet. With a new medium-porous carbon structure, researchers want to reach the point where the platinum particles stay where they are supposed to and don’t leave their position even after thousands of operational hours, in addition to retaining their original shape and characteristics.
The task of the DECHEMA research institute in the joint project is to develop platinum alloys and carbons which satisfy these criteria. For the manufacture of the carbons, the Frankfurt researchers have chosen a process that includes facilitating a more flexible configuration of the pore structure of the carbon as the substrate for the platinum.
Raw materials: a problem area
As a project partner, at Saarland University further carbon structures such as graphenoid are being evaluated for their suitability as catalyst carriers for platinum. The materials from the DECHEMA research institute and Saarland University are being tested in a laboratory fuel cell at the ZBT, another project partner in Duisburg. Graded catalyst layers are to be incorporated in Duisburg to increase efficiency.
While the demand for platinum for fuel cell vehicles is an issue, it does not bolster the argument for the combustion engine, as the bulk of today’s platinum demand already comes from the automotive industry in the form of 3-way catalytic converters. Specifically, from around 170t of processed platinum used today worldwide per year, approx. 95t is used for conventional 3-way catalytic converters.
Recycling platinum nanoparticles: a further research topic
At an average requirement of 30g platinum per vehicle for an 85kW electric engine, using today’s technology, the amount of platinum used for conventional drives in cars would be sufficient for only approx. 3 million fuel cell vehicles. This demonstrates how important advances in research for a more efficient use of platinum are. The recycling of platinum nanoparticles is therefore another key theme for research and development. Because of scarcity of resources, also for other future technologies – catchword: rare earths – a mix of batteries and hydrogen fuel cells lends itself to electric mobility (road) in future.
The institutes of the Zuse association, for example the Institute for Plastics Processing (IKV) from Aachen, are also undertaking research with supra-regional partners on other joint projects. This type of cooperation is also a topic of the unified Germany research series that the Zuse association accompanied with research highlights on the occasion of the 30-year anniversary of the fall of the Berlin wall with the hashtag “#FiVD”.
Link to the Gra2Kat project: www.dechema-dfi.de/GRA2KAT.html
Images: Transmission electron microscope images, each in the same position: While platinum clumps to a smooth carbon surface (black beads in image 2), it remains on a medium-porous carbon structure in its original structure (image 4). Image before (images 1 and 3) and after (images 2 and 4) 10,000 accelerated cycles. (Image source: Dr. M. Sakthivel; DECHEMA Research Institute)