Adib Mahbub from the team at the Center for Electrochemistry is first author of the paper.
Adib Mahbub, Debanjan Das, Wolfgang Schuhmann and Martin Muhler (from left) worked together on the study.
Catalysis How to recycle CO2 from flue gases
Design and process control are the be-all and end-all when it comes to reducing CO2 from flue gases or the atmosphere.
In order to protect the climate, the aim is to recover CO2 from combustion processes for valuable materials. This is challenging because there are other gases in flue gases besides CO2. An international research team led by Prof. Dr. Wolfgang Schuhmann from the Center for Electrochemistry at Ruhr-Universität Bochum, Germany, has shown how CO2 can be electrochemically reduced even in low concentrations in order to recycle it. They report in the journal “Angewandte Chemie” from December 23, 2024.
Unlike often under laboratory conditions, CO2 makes up only a small proportion of the gas mixture in flue gases or the atmosphere. In order to extract it under realistic conditions and reuse it as a valuable material, catalysis processes must therefore also work when the CO2 concentration is low.
Preventing competitive reactions
“Our problem is the competitive reactions that take place at the catalyst,” explains Wolfgang Schuhmann. “The fewer CO2 molecules there are to convert, the more likely it is that hydrogen will be produced during catalysis instead of the desired product.” If you adjust the electrolyte and choose a more alkaline solution to prevent this, you have a different problem: CO2 is converted to carbonate and is no longer available for the desired reactions.
Successful catalytic processes for CO2 reduction have already been described down to a CO2 carbon dioxide content of 10 to 20 percent. But what if the content is even lower? “By using a superactive catalyst based on nickel-copper, we were able to successfully catalyze the reduction down to a CO2 content of five percent,” says Adib Mahbub, the first author of the publication. Below this level, the researchers had to reach into their bag of tricks: By adjusting the electrical potentials and the electrolyte, it was then even possible to carry out the reduction from a gas mixture with just two percent CO2. “Although this means a loss of energy, clever process control allows us to access sources for the first time that we were previously unable to use for CO2 reduction,” says Wolfgang Schuhmann. “Future generations will have to build on such concepts if they want to extract CO2 from the atmosphere, where the CO2 content is even lower.