Not only the reduction of CO₂ emissions is considered an important measure for lowering the carbon dioxide content in the earth's atmosphere, but also the capture and storage of the greenhouse gas from the air. Accordingly, the current German government has also declared the development of CO₂ capture and storage technologies as a goal in its coalition agreement. In particular, it considers direct air capture (DAC) as a ?promising future technology for increasing negative emissions?.

Scientists at Friedrich Schiller University Jena now want to develop a method to filter carbon dioxide out of the air using electrochemical processes with renewable raw materials. As part of its CZS Nexus programme, the Carl-Zeiss-Stiftung is funding the junior research group led by chemist Dr Tilmann J. Neubert with around 1.8 million euros over five years.

Switching CO? storage?on and off

?We are utilizing a process based on electrochemical switching processes?, explains the chemist from the University of Jena. ?We want to develop a battery-like cell containing a functional molecule that can be switched on and off, binding carbon dioxide and releasing it again.?

The team primarily wants to use so-called quinones—organic molecules that consist of a ring of six carbon atoms with two oxygen atoms linked at two opposite corners by a double bond—which are also found in many natural substances such as plants. If electrons are added to this compound, the oxygen atoms become negatively charged and attract the slightly positively charged carbon in the CO₂—the carbon dioxide is stored. When this mechanism is deactivated, it is released again and can thus be enriched.

?In contrast to the usual methods, which use pressure or heat, for example, this technology is very energy-efficient and can be easily combined with electricity from renewable energy sources?, says Tilmann Neubert. This approach therefore has the potential to make DAC much more cost-effective.

Two challenges to overcome

In order to make the envisaged process efficient and sustainable, the scientists in Jena have to solve two key problems: Firstly, the system will only work efficiently in the long term if they succeed in reducing the amount of oxygen that the molecules also encounter. This is because oxygen can remove electrons from the process and trigger undesirable side reactions. Secondly, many components such as the electrolytes in such cells are often still based on non-sustainable solvents—aqueous alternatives must be found for this.

?If we overcome these two challenges, I am very confident that we will succeed in capturing more CO₂ than is produced by the process and thus enable negative emissions?, says the researcher from the University of Jena. ?In the long term, we need to conceptualize the emission, capture, storage and reuse of carbon dioxide as a circular economy in which all the components we put in should also be circular and renewable—from the solvents to the active materials.?

In order to be able to clearly prove that the method his team will develop is greener, it was important to Tilmann Neubert to also involve colleagues from the field of environmental engineering in the interdisciplinary project. ?We want to be able to calculate the carbon footprint of each step clearly and comprehensively in order to emphasize the sustainable nature of this future technology?, he says.

About the Carl Zeiss Foundation

The?Carl-Zeiss-StiftungExternal link has set itself the goal of creating scope for scientific breakthroughs. As a partner of excellent science, it supports basic research as well as application-oriented research and teaching in the STEM departments (science, technology, engineering and mathematics). Founded in 1889 by the physicist and mathematician Ernst Abbe, the foundation is one of the oldest and largest private science-promoting foundations in Germany. It is the sole owner of Carl Zeiss AG and SCHOTT AG. Its projects are financed from the dividends distributed by the two foundation companies.