Researchers present new and efficient conversion method

Greenhouse gas emissions are known to be the main cause of global warming. According to the Federal Environment Agency, around 666 million tonnes of carbon dioxide were emitted in Germany alone last year. All countries in the world have committed to reducing these emissions to zero in the medium term in various climate agreements. But climate scientists are already convinced that this alone is not enough. It is also necessary to recover, at least in part, the CO2 that is already floating in the atmosphere.

But what should we do with greenhouse gases? Numerous research teams around the world are working on it. Vietnamese researcher Cao Thang Dinh and his team at Queen’s University have invented an integrative system that can handle both the capture and conversion of carbon dioxide (CO2). His team promises that their method uses less energy than previous conversion processes.

In recent years, various technologies have been developed that can convert CO2 into other substances. In the “Carbon2Chem” project, for example, useful chemicals are created from carbon dioxide by breaking down the material and processing it. But CO2 is difficult to split and therefore consumes a lot of energy. This is often energy that is obtained from fossil fuels and can therefore cause more CO2 emissions.

Cao Thang Dinh is trying to make this process more efficient. He wants to use electricity to cause a chemical reaction. Carbon dioxide could be converted into carbon-neutral fuels using renewable energy. “This way we can store intermittent electricity in the form of gas,” the scientist explained at this year’s Falling Walls Scientific Summit in Berlin. “We can also convert carbon dioxide into a sustainable polymer material so we can permanently store CO2, which is a carbon negative process.”

The conversion of carbon dioxide requires a reactor in which the molecule goes through different phases: first it becomes a gas and then a solution before stabilizing on the surface of the solid, which serves as a catalyst. There the CO2 molecule breaks down into smaller molecules or atoms. They are then combined with other molecules to obtain various final products.

For the conversion to be particularly climate-friendly, various factors must be taken into account, such as energy efficiency, reaction speed or product selectivity. The target end product of Dinh’s experiments is ethylene, which is an important raw material in the chemical industry. The goal is to stabilize the conversion system so that high selectivity can be maintained over a long period of time. Until now, the best CO2 conversion system only lasted a few hours. Dinh and his team managed to discover the reason for the failure and let the process drag on for a longer period of time.

One of the reasons for the short duration of the process is the decomposition of the electrode into which the CO2 molecule is converted. That’s why the team reinvented the electrode structure. “We use a very stable polymer in combination with the active layer of the molecule and then cover this combination with a protective layer,” explains Dinh. With this system, the researchers managed for the first time to maintain high selectivity to ethylene for about 150 hours.

Dinh’s experiments also show that it is possible to expand the reactor to convert more carbon dioxide. In initial studies, the reactor was the size of a Rubik’s cube and was capable of converting about one gram of CO2 per day. The Queen’s University team has managed to build a microwave-sized reactor that can convert up to 2.5 kilograms of CO2 per day. “At this point, this is one of the largest electrochemical conversions of CO2 ever demonstrated,” says the chemist.

To convert carbon dioxide it is necessary to extract and purify it from the atmosphere, exhaust gases or industrial processes, which also consume a lot of energy. This happens in nature without human intervention. An apple tree, for example, takes diluted carbon directly from the air and converts CO2 into carbohydrates, creating an apple without the need to clean and separate the individual substances. The Vietnamese scientist is guided by this process.

Their research team has been working on a solution for about a year. The starting point of the experiments is concentrated and diluted CO2. This is collected in a solution and then introduced into the reactor as a solution. The gaseous product leaving the reactor is then continuously separated from the liquid. In the end, a concentrated product is created that can reduce energy costs for separation. The electrodes used in the reactor are crucial: depending on the material, reactors can be built that convert as much CO2 as 5 to 10 adult trees.

To convert carbon dioxide on a scale of millions of tonnes, a cost-effective and efficient system is needed. Dinh’s goal is to be able to increase elethylene selectivity from 75 percent to 95 percent and triple energy efficiency.

With his development, Dinh hopes to produce a chemical CO2 conversion system that can be used around the world thanks to renewable energy. “If we can do this, we will not only be able to reduce carbon emissions and curb climate change, but we will also give everyone, especially those in less developed countries, the opportunity to have access to clean energy, clean fuel, sustainable materials. and obtain sustainable energy. fertilizer.”