Water and electricity to produce hydrogen: this is the electrolysis of water, a reaction that many high school students have performed during chemistry practicals. A seemingly simple reaction, but "breaking down" the water molecules requires a substantial input of energy.
That's where catalysts come in! Or rather THE catalyst: platinum, used today to produce the hydrogen that drives hydrogen-powered vehicles.
But platinum is a rare and expensive metal, which slows down the large-scale development of this environmentally-friendly process.
Hence the need to find other catalysts, composed of abundant metals, which are stable, less expensive, but just as efficient as platinum.
Follow the scientists from the French HYKALIN consortium, who have come to the SAMBA beamline to test new catalysts for this hydrogen production reaction.
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Voice over
A container filled with salt water with an electric current passing through, and the bonds of the water molecule give way, leaving behind hydrogen on one side and oxygen on the other.
Does this experiment remind you of anything?
This is the electrolysis of water that high school students around the world have performed during chemistry practicals.
Marion Giraud. Chemist et Assistant Professor. Université Paris Cité.
It sounds pretty simple because the balanced equation of the reaction is not very complex, however, it requires quite a lot of energy to perform electrolysis and really break down this molecule.
That's the reason we need catalysts, to reduce the amount of electricity required.
Voice over
An efficient catalyst for this reaction already exis ts: platinum, the substance that is currently used to produce the hydrogen which powers hydrogen vehicles. However, this metal is rare and expensive, which slows down the progress of this large-scale environmentally friendly process.
Marion Giraud
So, essentially, we're looking to find alternatives to platinum, particularly those which are less expensive while remaining highly efficient, and based on metals which are widely available.
That's why we're interested in bimetallic nickel-based catalysts, which is less of a limiting factor than platinum in terms of availability.
Voice over
In order to measure the efficiency of bimetallic catalysts composed of nickel and a small amount of ruthenium, researchers are currently performing experiments on the SAMBA beamline of the SOLEIL Synchrotron, a beamline which allows the structure of the materials to be studied thanks to X-rays.
Marion Giraud
This tool is crucial for us. It allows us to perform what's known as operando spectroscopy, that means observing the catalyst under actual working conditions.
Benedikt Lassalle. Beamline scientist. Synchrotron SOLEIL
Very often people who read our articles and make comments ask us if we've been to the synchrotron to record data, to find out whether the catalyst that we're studying remains active throughout the catalytic process.
Because that's the big question: we can create catalysts which we imagined on paper or through calculations, but reality is sometimes quite different.
Voice over
On today's agenda, observing in real-time the action of the two constituent metals of this new catalyst, each having a well-defined role in the water electrolysis reaction.
Marion Giraud
These two metals work in concert to accelerate and facilitate the reaction.
We hypothesize and try to demonstrate through the experiments we do at SAMBA, that ruthenium will first adsorb the water, breaking this OH bond to form hydrogen atoms, which will then go to the nickel catalyst making them react together to form dihydrogen.
Live (B.L., F.D.)
- Reference materials, and samples?
- Yes, there are different compositions of nickel and ruthenium.
Voice over
Researchers begin by taking reference measurements thanks to the powerful X-ray beam of the beamline, and then move on to the catalyst. This catalyst is deposited on an electrode in the form of an ink and is then integrated into a cell which resembles a mini electrolytic cell.
Marie-Sophie Dias Fernandes. PhD student in electrochemistry. SOLEIL/École Polytechnique
So here in the central square, is where everything happens, and here the electrolyte enters through a pipe. The beam is aimed directly at the centre, it will first hit our working electrode where we deposited our materials. It will hit at a 45° angle, and then bounce off.
Benedikt Lassalle
First, we'll observe an element, for example ruthenium, we'll first take a look at ruthenium.
The X-rays will excite the electrons, which will lead to a number of physical and chemical processes, and thus a relaxation which results in photons being emitted, and we'll measure these photons in a process known as fluorescence, we'll measure these photons and that gives us information about this element ruthenium. Is it oxidised? is it reduced? is it small or large? what does it have around it?
Voice over
After several hours of measurements to detect the rare fluorescence emissions of ruthenium, it will be nickel's turn.
Live (B.L., M.G.)
- I think we can move the detector forward a bit more.
- Ah! It's good! That's the first scan.
Voix off
Ultimately, the scientists of the French consortium HYKALIN hope to be able to identify the composition and structure of the most efficient and stable bimetallic catalyst, a catalyst which is at least as good as the one currently in use in hydrogen vehicles.
Marion Giraud
That's the case here. We get catalysts which are just as efficient as those which can be made with platinum.
Benedikt Lassalle
When researchers come here and leave with good data, understanding some things which they didn't understand before and which they can only get here or, let’s say, in a synchrotron, that's when we feel really useful.