Sustainably on the road...

Heraeus and DECHEMA research institute collaborate to recover platinum from PEM fuel cells at the end of cell life. Closing the platinum loop would push e-mobility and is a prime example for circular economy.

Someday the coal rooms of steamers and the tenders of locomotives will, instead of coal, be stored with these two condensed gases (hydrogen and oxygen), which will burn in the furnaces with enormous calorific power.” Jules Vernes was quite the visionary, when he described the future of transport vehicles as early as 1875 in his novel “The Mysterious Island”.

We have learned since that bringing hydrogen and oxygen next to each other is not advisable, and using electrochemical process in fuel cell technology is much safer. Trains get indeed attention as fuel-cell-powered vehicles. As of now, cars and buses in public transport are yet major applications.

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is the most efficient option for transportation such as passenger cars, busses and regional trains. This technology, however, still relies on the expensive precious metal platinum as catalyst for both hydrogen oxidation and oxygen reduction reactions. Around 190 tons of platinum are mined per year worldwide, from which 40 % are used in catalytic converters for exhaust systems of combustion engines. If only 100 t platinum per year is available for new hydrogen transportation technologies inclusive PEM electrolysis, a systematic and efficient recycling strategy for catalyst reuse is a prerequisite for a long-term, sustainable H₂ economy. While thermal recycling of catalytic converters is quite straightforward and state-of-the-art, recovery of about 30 grams of the precious metal from a 115 kW fuel cell stack (e.g. Mirai, Toyota) remains still challenging not only technically but also economically.

Heraeus and the DECHEMA research institute have now joined their expertise to work on platinum recycling from fuel cells in the project Pt2Go2Pt and thus ultimately help to push e-mobility.

Christian Gebauer, Head of Hydrogen Systems at Heraeus Precious Metals says “Although we at Heraeus have decades of experience in precious metal recycling, the end-of-life material streams from PEM fuel cells raise new challenges. With this project, our Recycling Innovation department is taking a closer look on their specific properties and aim to close the gap between scientific lab experiments and industrial processes.”

The experts at DECHEMA research institute are exploring whether the platinum in gas diffusion electrodes and catalyst-coated membranes can be dissolved by applying high cathodic polarisation in alkaline solution. Another important step towards sustainability is to extend the life of the catalyst particles during fuel cell operation by using mesoporous carbon as support. Since no commercial products fulfil the required properties yet, DFI team is also developing mesoporous carbon with an optimised pore size.