The electrochemical reduction of carbon dioxide is an attractive solution for combating climate change. Now researchers at the University of Szeged in Hungary have found an integrated solution to address this reaction in a continuous flow, to overcome long-term stability problems and to enable a scalable process.
Using electricity to recover carbon dioxide has served two purposes. It lowers emissions while providing the chemical industry with an alternative source of carbon for producing valuable raw chemicals such as carbon monoxide, formic acid and methanol. However, several hurdles have blocked the adoption of these technologies. Among other things, it requires a very basic reaction environment that contributes to the formation of precipitates that affect the stability of the electrolyzer and impede continuous operation.
“We have discovered a new regeneration and activation process that reduces this inefficiency and enables our electrolysers to work in a continuous flow for over 200 hours,” says Csaba Janáky, who led the study. ‘In addition, our concept will attract the chemical industry. We have shown that it extends the life of membrane electrode assemblies and tested its scalability. A prototype of a multi-cell device that works at high current densities was developed. ‘The team is working with the start-up ThalesNanoEnergy on industrial applications.
Electrolytic cells for carbon dioxide reduction borrow some of the concepts and mechanisms from hydrogen fuel cells. In these devices, a membrane separates the two electrodes, but allows ions to permeate and keep the reaction going. However, this mechanism also led to undesirable by-products. Certain ions such as potassium migrated through the membrane to the cathode and led to the formation of insoluble salts. “Until now, people have tried to improve performance by increasing the amount of base electrolytes,” says Janáky. Unfortunately, this meant adding more cations to the mixture, which eventually led to undesirable precipitates.
In attempting to solve this, the researchers found that basic electrolytes like hydroxides increased efficiency but contributed greatly to the formation of precipitates. Potassium, on the other hand, increased the response – as long as the pH was controlled to avoid the accumulation of salts. Then they created a system that feeds pure water around the anode and adds potassium solutions to the cathode. Together, this prevents the production of precipitate and allows cells to produce carbon monoxide without interruption in performance, explains Janáky. In addition, they observed that other alkali ions also activated the electrolytic cells. “We have used cesium in all of our long-term tests, which significantly outperforms potassium,” he adds.
‘The successful implementation of CO2 Reduction technologies require developments at various levels, including catalyst, mode of operation and device, ”says Núria López from the Institute of Chemical Research in Catalonia, Spain. ‘They found a connection between all these three elements and managed to stabilize the catalyst with a clever surgical technique. Your device is rugged and a wonderful example of integrated engineering. ‘López hopes that in the future, further mechanistic studies and simulations will help to understand the true role of electrolytes in this reaction.