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CO2 – From greenhouse gas to value-added product | Technical University of Vienna

Group photo: Apaydin, Eder, Rabl.

If you convert CO2 into synthesis gas, you get a valuable raw material for the chemical industry. Researchers at TU Wien show how this works even at room temperature and ambient pressure.

Anyone who thinks of CO2 will probably quickly think of terms such as harmful to the climate or waste product. While CO2 was there for a long time - a pure waste product - more and more processes are being developed with which the greenhouse gas can be converted into valuable raw materials. The chemistry then speaks of "value-added chemicals". A new material that makes this possible was developed at the Vienna University of Technology and recently presented in the journal Communications Chemistry.

Dominik Eder's research group developed a new material that facilitates the conversion of CO2. These are MOCHAs - these are organometallic chalcogenolate compounds that serve as catalysts. The result of the electrochemical conversion is synthesis gas, or syngas for short, which is an important raw material for the chemical industry.

CO2 becomes synthesis gas

Syngas is a mixture of carbon monoxide (CO), hydrogen (H2) and other gases and is used as a raw material for other substances. One of the most important fields of application is fertilizer production, in which ammonia is produced from synthesis gas. However, it can also be used for the production of fuels such as diesel or for the production of methanol, which is used in fuel cells. Since the extraction of CO2 from the atmosphere is quite energy-intensive, it makes sense to extract CO2 from industrial plants. From there it can therefore serve as a starting material for various chemicals.

However, previous methods require high temperatures and pressure as well as expensive catalysts. The Viennese researchers therefore searched for catalysts with which syngas can also be produced at low temperatures and ambient pressure. "MOCHAs work differently than the catalysts used to date: Instead of heat, electricity is supplied to activate the catalyst and initiate the conversion of CO2 into synthesis gas," explains Junior Group Leader Dogukan Apaydin, who is in charge of CO2 conversion methods in the research group researches.

MOCHAs as problem solvers

MOCHAs form a class of materials that were developed almost 20 years ago, but have not yet found any application. The organic-inorganic hybrid materials have therefore only gained popularity in recent years. The TU researchers recognized the potential of MOCHAs as catalysts and carried out experiments with them for the first time. However, they faced a number of problems: Previous synthesis methods only produced small amounts of product and required a lot of time. "Using our synthesis method, we were able to significantly increase the amount of product and shorten the duration from 72 to five hours," explains Apaydin the novel manufacturing process for MOCHAs.

First tests showed that the catalytic performance of MOCHAs in the production of synthesis gas from CO2 is comparable to that of the previously established catalysts. In addition, they require much less energy since the entire reaction can be carried out at room temperature. In addition, MOCHAs have proven to be extremely stable. They can be used in different solvents, at different temperatures, or under different pH conditions, and retain their shape even after catalysis.

Nevertheless, there are some parameters that the team around Dogukan Apaydin and the doctoral student Hannah Rabl are still researching. Using the same electrodes multiple times to deliver energy in the form of current shows a slight drop in performance. How the connection between MOCHAs and electrodes can be further improved to prevent this drop in performance is now being researched in long-term experiments. “We are still at an early stage of application,” Dogukan Apaydin points out. “I like to compare this with solar systems, which 30 years ago were much more complex and expensive to produce than they are today. With the right infrastructure and political will, however, MOCHAs can also be widely used in the future in the conversion of CO2 into synthesis gas and thus make their contribution to climate protection," Apaydin is certain.

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