Over 40 billion tons of CO2 are emitted every year due to human activities. What can we do with this waste?
In Nature, plants capture CO2 and transform it into plant material (biomass) thanks to solar energy. It’s photosynthesis.
At the Institut de Chimie Moléculaire et des Matériaux (Orsay), the scientific team called « artificial photosynthesis » is inspired by this natural phenomenon in order to transform CO2, not into biomass but into clean fuels such as methanol or methane. This team comes to SOLEIL, at the ROCK beamline, to find out what are the best catalysts of the chemical transformation of CO2, that is to say the compounds that will achieve this artificial photosynthesis quickly and efficiently.
Water, air… and clean fuels
Audio Transcription
VOICE-OVER
Factories and vehicles are emitting ever more carbon dioxide into the atmosphere.
Over 40 billion tons of CO2 are emitted every year due to human activities.
How should we react to the situation? What can we do with this waste?
Zakaria Halime - chemist and CNRS researcher - Institut de Chimie Moléculaire et des Matériaux d'Orsay
Today, several laboratories are researching solutions that will both capture CO2 that is reaching rather high concentrations in our atmosphere, and transform this CO2 into added-value molecules.
VOICE-OVER
Nature has the solution. It achieves this task using photosynthesis. Plants can actually capture CO2 and transform it, thanks to solar energy, into plant material or "biomass".
A concept that has set researchers thinking about new approaches.
Zakaria Halime
There is a small team called "artificial photosynthesis" that is inspired by all the steps of photosynthesis to achieve our aim, which is to use light energy to transform CO2, not into biomass but rather into clean fuels such as methanol or methane.
VOICE-OVER
There is a downside, however: the carbon dioxide molecule is highly resistant to any transformation. And that is because the bonds between the carbon and oxygen atoms are very... very strong.
In order to break them, researchers need the help of a catalyst.
It was just this challenge of finding THE ideal catalyst - the compound that will achieve this artificial photosynthesis quickly and efficiently- that inspired Zakaria Halime to work with Benedikt Lassalle on the ROCK beamline of the SOLEIL synchrotron.
Benedikt Lassalle - chemist and beamline scientist - Synchrotron SOLEIL
We will be looking at iron porphyrins.
Zakaria Halime
... bio-inspired catalysts, because this type of complex -or molecule- is already used by nature.
Benedikt Lassalle
These catalysts are promising enough but people are seeking to improve them.
In order to do so, we have to be able to understand the reaction mechanism, how the catalytic cycle occurs, and what the structure of these catalysts is.
VOICE-OVER
During the reaction, the catalyst will try to "capture" the CO2 molecule and to "tear away" its oxygen atoms. These exchanges between the catalyst and the CO2 molecule can be monitored by X-ray spectroscopy.
Benedikt Lassalle
Quite often, the catalysts are observed before and possibly after the reaction, but we are trying to watch them during the CO2 reduction reaction to have an idea of their structure when they are active.
Zakaria Halime
We have a reaction that occurs very quickly, there are hundreds of thousands of reactions per second. And we are going to try and take photos during a cycle.
But you also need enough of these photos, to retrace the whole story.
Benedikt Lassalle
So it is all these steps, during catalysis, that we are going to try and watch by using the time resolution available on the ROCK beamline.
VOICE-OVER
A solution containing CO2 and the catalyst will circulate in an "electrochemical cell" especially designed on a 3D printer for the experiment.
That is where the X-rays will probe the material states and will provide the researchers with valuable information on the catalyst's operating mode.
The very detailed analysis of this chemical transformation is essential for any attempt to improve the catalyst's efficiency. Making it more selective and faster and reducing its energy consumption. Because the aim is to be able to obtain fuel thanks to solar energy alone.
Benedikt Lassalle
We can already reduce CO2 into CO reasonably well. But it isn't a target that is industrially or economically very interesting. Methane is much more interesting.
If we could make methanol, ethanol and other chemical compounds or fuels with a higher added value, that would be interesting.
VOICE-OVER
There is still a long way to go to successfully match nature's ingenuity; to capture CO2, and to do so effectively. Because industry needs time. Several decades of research are undoubtedly still necessary to obtain clean fuels or "zero emissions".
Zakaria Halime
The research we are doing today won't totally solve the problem.
We are looking for ways to capture and transform CO2.
But that shouldn't stop us from reducing our consumption of fossil fuel.