María Retuerto has spent years studying how to combat climate change by storing renewable energy that we do not use. Her contribution has earned her the «Women For Science» Research Award, awarded by the L’Oréal Foundation and UNESCO.
As if it were a rebound effect, María Retuerto (Madrid, 1981) found her vocation during her adolescence, following a failing in chemistry. «She had never failed anything and she made me get so excited that, understanding the subject so well, I ended up delighted,» she recalls.
With a PhD from the Institute of Materials Science of Madrid (ICMM), she stayed in the capital for two years with a postdoc until in 2010 she obtained a Fulbright scholarship at Rutgers University, in New Jersey (USA). Four years later she returned to Europe to settle at the Niels Bohr Institute in Denmark, where she spent a year doing research. Already in 2015, and through a Juan de la Cierva contract, she returned to join her current center, the Institute of Catalysis and Petroleum Chemistry ( ICP ) of the CSIC.
Since then, Retuerto has focused his career on the development of technologies that allow clean energy to be stored through green hydrogen. Specifically, through the polymeric membrane electrolysis system, which for her is «the most efficient method of producing hydrogen from renewables», but also expensive and short-lived. To round off her career, the L’Oréal Foundation and UNESCO have recognized Retuerto’s career with one of the For Women in Science Research Awards, awarded annually to five eminent Spanish scientists.
What does this award mean to you?
It is a total recognition of the scientific career, an important award for women that recognizes the effort, work and perseverance. The scientific career is very long and difficult, and many times you feel like giving up. In Spain there is very little financing and it is very difficult to stabilize. Therefore, this award gives you another starting point to get things.
In these times, in which the problem of precariousness in the field of science is being addressed a lot, what is the situation of your group like?
I worry that my daughters decide, for example, that they want to do engineering and that they don’t see themselves capable of it because they are girls
I have been lucky to stabilize in the last year. I have taken the position of titular scientist with 41 years. I read my thesis twelve years ago, I have been five years in the US and Denmark and I have worked for many years. It seems impossible, but with effort and work you can get there. For a young person, who is starting the thesis and considering a research career, it is very discouraging. It’s a shame, because we lose a lot of highly educated people who leave or stay abroad. Here we are not fully aware of this loss.
As you say, you would like to teach your daughters that they can do anything if they are really excited about it. Are you afraid that if they follow the path of science they will have to go through so many obstacles?
Working life in Spain, in general, is not easy. But I’m not going to tell them not to. It is true that I have experienced a particular precariousness, but I want them to dedicate themselves to what they really want and not to feel conditioned by their gender. That does scare me. I worry that they decide, for example, that they want to do engineering and that they don’t see themselves capable of it because they are girls.
Your profile can be a great example for girls like them…
I think so. However, I admit that to feel comfortable in the field of hydrogen I have needed more time than a man, especially until I have obtained the position. I don’t know if that insecurity has been particular to me, if it has been educational or innate due to the fact that I am a woman.
I admit that to feel comfortable in the field of hydrogen I have needed more time than a man, especially until I have obtained the position
Now, with the square, this award has made our research more visible. With European funding is when you realize that we can form a larger group and carry out the research that we want to carry out.
In short, this award has functioned as a showcase in which to make your line of research visible and known.
It’s fundamental. In my particular case, it has been linked to the current good moment of green hydrogen. In Spain, in the last year, the Hydrogen Industry Sectoral Agenda or the Hydrogen Roadmap has been created . It all goes together. Also, I remember that I decided to return to Spain because I wanted to do this.
How was that process of return to Spain?
Due to my training, I came to the Institute of Catalysis and Petrochemistry, where they studied materials and their properties in a very deep way. I realized that the ones that I had studied the most were oxides, which are very useful for one of the reactions that occurs in the electrolyzers that I am studying now. From my point of view, the people who did catalysis overlooked a good understanding of the materials. He believed that he could contribute that part of fundamental knowledge. So I joined an electrochemistry group and introduced that deep characterization part. We have made a very good union and we have come a long way.
dissociation of water into hydrogen and oxygen
What does that electrochemistry group do?
What we do is electrolysis. We separate the water into hydrogen and oxygen with the help of an external electrical current, coming from renewable energies. All that energy used is accumulated in the form of hydrogen.
What we do is electrolysis. We separate the water into hydrogen and oxygen with the help of an external electrical current, coming from renewable energy
How does this method of accumulating energy differ from other conventional ones?
The normal thing is that the renewable energy that is not used is lost. When you have wind, you connect the turbine and let electricity through. But if the grid doesn’t need more electricity, it’s lost. It also happens a lot with solar energy. In summer, and especially in peak midday light, the network does not need as much and we lose it.
Now electricity is usually stored with hydroelectric pumps or batteries, for example. However, the ideal way is to accumulate that energy in the form of hydrogen. This method is an extra advantage over other storage modes. It is not only used to generate electricity later, through fuel cells, but it has other uses.
For example, it can be used in certain industrial processes that require hydrogen, such as for the creation of fertilizers or biofuels. Also to introduce a certain percentage (between 5 and 7%) into natural gas lines or to burn it in industrial processes that need heat. In short, it can be introduced in energy sectors such as industry or transport.
Now electricity is stored with hydroelectric pumps or with batteries, however, the ideal way is to accumulate that energy in the form of hydrogen, which is an extra advantage
In all that equation, where does your work come in?
It consists of improving the efficiency, durability and price of the electrolyser, which is the device that directly transforms renewable energy into hydrogen. By powering this device, it splits water into hydrogen and oxygen. There are four technologies for electrolysis. What I do is called ‘polymeric membrane electrolysis’.
How does this technology work?
It’s like batteries, with two reactions running on two separate electrodes. On one side the reaction of hydrogen formation occurs and on the other that of oxygen. Compared to conventional technology [alkaline] it is a solid technology, which gives it several advantages: it is not necessary to heat any liquid, so it does not lose that efficiency; Being a solid system, it’s very compact and you can stack the cells and quite efficiently get a lot of hydrogen.
The efficiency of this technology today can reach 80%. Although other methods may be more efficient, they need to be associated with other additional systems, such as batteries.
Finally, the same compactness makes it possible to work with high pressures and the hydrogen comes out pressurized and with more purity, ready to put it in tanks and store it. That is, it avoids the need to install a compressor.
The efficiency of this technology today can reach 80%. Although other methods may be more efficient, they need to be associated with other additional systems, such as batteries. Therefore, it is the most suitable technology for accumulating renewable energy.
But they are not all advantages…
It has several drawbacks, but one particularly big one. Noble metals are used for both electrodes, which are very expensive and scarce materials. On the side where hydrogen is generated, platinum is used; in the other, iridium oxides, whose economic value triples that of platinum. Yesterday I looked at the price and it is 128 euros per gram. Also, much more iridium is needed than platinum.
Are these metals the ones marked on your target?
I designed a material in which I changed the oxidation state of the ruthenium to increase its durability and we got it. Although there was no commercial interest in that finding, it represented a very great advance
I try to eliminate or reduce the iridium a lot. There are four or five compounds studied worldwide that manage to dissociate hydrogen and oxygen, but at very high potentials. That is, they need a lot of energy. With which, it does not make sense either because it is not efficient. What I’ve been able to do is lower the amount of iridium from 80-70% to 30-20%. We have also managed to replace it with cheaper ruthenium.
How?
Iridium oxide has a certain crystallographic structure. What I do is design materials that have different structures, where apart from the iridium I put other elements. I modify the environment of the iridium so that, for example, it has a different valence, position, or environment. In short, I force iridium to favor oxidation reactions.
What has been your greatest contribution?
I would say the publication in Nature magazine on ruthenium. Ruthenium oxides are undoubtedly the best catalysts or electrodes for this reaction because they are very active. With very little energy they generate oxygen. But they are very unstable. They last for one reaction cycle, which can be equivalent to one second. In that article I designed a material where I changed the oxidation state of ruthenium to increase its durability and we did just that. Although there was no commercial interest in that finding, it was a great advance. He shows that if you can change the ruthenium environment, maybe you can get something stable.
What are the next steps you have planned and what is the ceiling?
This is my main line of work and for which I have received the award, but it is not the only one. We also work on fuel cells or the reaction of hydrogen in electrolysis. For me, the ideal would be to eliminate noble metals. I don’t think it’s impossible, but we’re still a long way off.
The ideal would be to eliminate noble metals. I don’t think it’s impossible, but we’re still far away
If achieved, how much could the cost of obtaining hydrogen be reduced through this electrolysis system?
It’s hard to know, but a lot. Three factors intervene in its price: the cost of materials, the production of electrolysers and the price of energy. For a large one megawatt electrolyser you need one or two kilos of ruthenium, about 300,000 euros. Just by reducing the iridium by up to 20%, maybe the price will become 70,000 euros. Electrolysis itself is also expensive because it is also not produced in large quantities. There is also the part of the price itself of renewable energy. When it decreases, those who emit CO₂ are penalized and those who do not benefit, it will be established.
When can we see this project transferred to daily life?
It is already being used. In Japan there are many projects running with this method. In Spain, on the other hand, there are at least three projects by large energy companies to generate green hydrogen through alkaline electrolysis, with batteries or much more complex systems.
To pollute less, we need renewable energy. And for all that we need, we would have to install many panels and mills. What is done is trying to accumulate the energy that we do not use
If we were able to change the energy model towards one in which polymeric membrane technology was viable and had a greater presence, how could society benefit?
To pollute less, we need to have renewable energy. And for all that we need, we would have to install many photovoltaic panels and windmills. It would be crazy. For this reason, what is done is to try to accumulate what we do not use, which is already a lot. I am not saying that it is going to be an energy model based only on hydrogen, not at all, but that it is going to be combined. We are going to continue using batteries, biomass and also fossil fuels for many years to come. But hydrogen will be a fundamental element.
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