No detour via hydrogen: TU Berlin wants to turn CO₂ directly into raw materials

For synthetic fuels, hydrogen is usually produced first with green electricity and then processed with CO₂. Researchers at TU Berlin led by Peter Strasser, head of the Chair of Technical Electrochemistry and Electrocatalysis, are betting on direct CO₂ electrolysis: carbon dioxide reacts with water directly in an electrochemical cell to form chemical precursors. "Our key reactions for this are already running in the lab," says Strasser. "Now it is about making the electrolysers more efficient, more durable and larger." His chair is receiving a total of around 2.6 million euros for two new projects.

In the JEThylen project, coordinated by Siemens Energy with Fraunhofer IGB and Bauhaus Luftfahrt, CO₂ is to be turned directly into ethylene – a feedstock for synthetic jet fuel. The aim is to cut the cell voltage from about 4.5 to around 2.5 volts, raise energy efficiency from about 27 to 50 percent and run stably for at least 1,000 hours. Instead of lab electrodes of around 10 square centimetres, cells of several hundred square centimetres are to run; concepts target up to 0.5 square metres. The project is funded by the German research ministry and runs until February 2029.

The second project, INNOCELL, builds on a patented cell design with gas diffusion electrodes developed at TU Berlin. Water-repellent plastic substrates are meant to stop the pores from filling with electrolyte – a problem known as 'flooding'. Tests run at 60 to 80 degrees Celsius and up to 30 bar; the targets are at least 500 milliamperes per square centimetre, 45 percent energy efficiency and 1,000 operating hours. Besides ethylene, the work also covers carbon monoxide, a feedstock for methanol and synthetic fuels.