Fallings Walls: How Heterogeneous Catalysis Can Replace Fossil Fuels

Breaking the Wall of Energy Supply.
How Heterogeneous Catalysis Can Replace Fossil Fuels

by Robert Schlögl, Director, Fritz Haber Institute of the Max Planck Society, Honorary Professor, Humboldt-Universität and Technische Universität Berlin, Germany.

Enerchem is an innovative research association initiated by the Max Planck Society that, instead of specializing in a particular scientific subject, focuses on issues that are commonly recognized as relevant across society. The project takes the well known topic of sustainable power supply, extrapolates the scientific problems that lie at its core, and spans across a multitude of research fields to find a concerted solution to challenges like the chemical foundations of a hydrogen-cycle economy, the development of nanochemically optimized materials for mobile energy storage, and models for effective decentralized production of energy. To oversee researches in the field of inorganic chemistry, Max Planck Society selected Robert Schlögl, who has authored approximately 500 publications, is a registered inventor of more than 20 patents, and is internationally recognized by organizations like the Royal Society of Chemistry for his investigation of heterogeneous catalysts based upon inorganic solids. At Falling Walls Prof Schlögl explained how his efforts to bridge the gap between surface science and chemical engineering in the field of oxidation catalysis will help realize the dream of renewable energy.

Taped Text:

Presentation: Energy Falling Wall Schlögl
The first message I would like to bring you is that of energy, which you would not normally relate to chemistry. I am a chemist, and in the next fifteen minutes I will be dealing with energy. The second message is: we use the term “falling walls”, but walls don’t fall; walls have to be torn down, and you have to do it yourself. So, here I bring you a piece of the Berlin Wall from the Brandenburg Gate that I tore down myself on the 10th of November some time ago.

Now, back to energy, fossil energy: is it always at hand? We seem to think that it is. Here is a nice little question for you: who knows why this flame is blue? (referring to presentation) If you can answer this question, tell me in the break. Fossil fuels are not only nice because they are blue, but they also emit a lot of CO2. I’ll show you a bit of interesting data (referring to a pie chart): the big part, of course, is our friends from America; the dark blue ones, our friends from China; the yellow one is the Internet and the red one is Germany. So, you see roughly where CO2 is emitted from. There is also an enormous amount of emission from sources that you would not normally think are emitting CO2.

So, where is the wall to break now? Why do we have to store the Sun on Earth? In order to understand this, I’ll show you a simplified structure of our energy supply system. (referring to presentation) We have consumers: this means electricity generation, mobility and transport, and heating and process energy. We have sources of energy: fossil carriers or gas coal, nuclear power; and then we have renewable energies (these are the green ones): hydroelectric, wind, photovoltaics and biomass.

This is a nice conglomerate; now how do we bring it to order? How does this work today? It works with two processes. One is combustion; almost all of the energy that we use is generated by combustion, and that generates the CO2 that I showed you. It works through these distribution systems, and here I only used the grid in order to show how it works. There are many details to be explained about the present system, but this is the simplest way possible to see what the structure of the issue is.

Now, this is the consumption of electricity in Germany about two years ago. You see several things. First, you see these noises; these noises are the weeks. On Sundays and Saturdays we don’t work, so this is the reason why consumption goes down on these days. Secondly, you see all the red, black and yellow colours: this is the fossil fuel that we use. We see this little bit of blue on top of it; this is regenerative energy. That’s all that we have. We plan to replace all of the red and black ones, but you will understand very quickly why this is an enormous challenge. We are far away from being able to do this quickly.

So, what do we find if we try to break that wall? We find the question: how do we store energy in order to be able to use solar radiation seven days a week, 24 hours a day? Now storing energy unfortunately requires chemistry, so I have to give you a little bit of a science lesson here. On this energy diagram, you see two chemical reactions that use water and CO2 and produce an energy storage molecule. Nature also does this. We tend to use methanol. If there are six methanol molecules, then we get sugar. Sugar is the storage molecule of nature, and as you listen to me, I am showing you some of these storage molecules, because energy storage is related to sugar (corn sugar is handed out to the audience). So, everyone should now eat a little piece of sugar and then you can follow me through the rest of the presentation.

Now, once we have all this sugar, then, of course we’ll want to use it. I will show this in the next slide. You have to invest some energy in order to store energy. The blue arrow tells you how much energy you can store. You can also get this back. That is the blue arrow on the other side. You then have red arrows; this is the price that you must pay in order to deal with chemical reactions. Unfortunately, at present, this price is much too high. It is this large red bar you see here (referring to presentation). On the other side, where you use energy, you also have a red bar. Please don’t remove that one, because if you were to remove it your sugar would spontaneously burn in the air and you would hurt yourself. So, some of these red arrows are good, but some of them are very bad.

The job of my science is to remove this red arrow that you see on the right-hand side down into this green curve. This is all that is behind the science of catalysis. We can break the wall of energy supply if we create artificial solar fuels, like nature uses sugar. So, if you eat this nice little piece of sugar, you take in energy that has been created somewhere in nature. This is solar energy at your fingertips.

Now you might think: “Why don’t we use this? Then we would have solved all the problems.” The energy density in this sugar is unfortunately not high enough for us. We need much more energy per volume. This is why we need other processes. So, here is your sugar. This is not a wall of sugar; this is the tangible form of energy storage from nature.

If we are going to do this, then we don’t use sugar; we use hydrogen. We tried to use electricity first, in the last couple of decades, to make hydrogen either from light or from electrical power. Then we used a solar refinery; this is a big new chemical factory that produces energy storage molecules, as you use sugar. We use methane, methanol or ammonia, and then we replace fossil fuels with solar fuels in our diagram, and then eventually everything is fine.

This sounds very simple, so why don’t we do this? There is a slight problem. The hardest part of this wall is actually the hydrogen generation that you see here in the laboratory. It works beautifully from electrolysis, but you cannot scale this. It is impossible to build a big machine that generates hydrogen by this process. I will explain to you why.

Can we split our water molecules? You might ask how we do this. The chemist tells you that there are chemical bonds between atoms and that what we want to do is store the energy by just moving these black lines (referring to presentation) from the orientation of water to the orientation of hydrogen and oxygen. You say: “Oh, that is very easy; you just moved the lines.” Remember: you have to pay a price for this. This is the big thing. This price is so high at the moment that the platinum that they use as a catalyst is destroyed when you move the bonds. That is the reason it doesn’t work.

What do we have to do to make our future science a reality? We have to use better catalysts like nature does. In these green leaves that you see, you also have catalysts, but we need better walls. Now imagine: nature took billions of years to develop, as you heard in one of the talks before. Now we have 20 years to develop something that is better than nature made it in four billion years. So, hopefully we are going to do that. It is a big challenge.

How do we do that? We use a metal that is not platinum – over the last few decades we have come to understand that the metal must not be flat, but must have steps in corrugations. In these corrugations, you can see that the water molecules fit beautifully; they just like to lie there. When they lie there, and we have the ability to bring a so-called co-catalyst (these are the pink atoms here), then the bonds will spontaneously start to flip. So, what we have learned is that we have to use appropriate catalysts in the appropriate structure. The structure is a so-called nanostructure. This nanostructuring is something that we have to learn how to do.

Can we make solar fuel once we have the hydrogen? This is not enough, because hydrogen is a gas that explodes, that has very negative properties, so we cannot use it as direct energy storage. We would rather make our artificial sugar. We do the same trick. We take a CO2 molecule, and use another catalyst. This catalyst is quite lively. This catalyst is capable, again, by steps of bending the CO2 molecule. CO2 is a straight molecule. It is straight, and it is very stable. If you bend it, it becomes reactive. So the trick is to just bend it around, and then bring in some hydrogen atoms, and then automatically the hydrogen atoms will react with this bent CO2 molecule and make our solar fuel: methanol. This sounds, again, very easy, but the difficulties lie in finding these materials and understanding the details of the nanostructure in order to be able to do this.

Now, here is how we break down the wall (referring to presentation). This is just a hole through the wall. This is a catalyst that you can actually see in your microscope, and you can quite nicely see that there are a lot of nanostructures in there. You see the hole in the wall there. If you go a little bit closer then you can actually see the steps that we see here. This is an advantage that we have had in the last couple of years: the tools that we have at hand are so much better than they used to be, that we can now see the steps that are only one or two angstroms high – less than an atom thick.

We are doing even better now. Here, on my last slide, you see every individual atom of a catalyst, and you can quite clearly see that we have really been able to make steps in our catalyst. You see atom per atom; there are steps in between, and there are a large amount of atoms that we cannot use. But, some of these atoms are at the surface, where the steps are; they are the active sides. The art is now to understand how to control this for any type of material that we want to make. This is where the future challenges lie.

If we summarise this, then we can quite clearly say: “Yes, we can break the wall of energy supply when we remodel our energy system.” We need only 0.17% of the earth’s surface in order to generate all the energy that we need from solar radiation. So, it should be doable: 0.17%. When we come back to it: is this a lot or a little? Through a combination of physical and chemical technologies we now have to harvest this in order to use renewable energy. We do this with solar energy, with photovoltaics, wind, and with all these emerging technologies. But that is not enough. What we have to add to this system is the ability to store large amounts of this energy in chemical bonds – and it has to be chemical bonds, because all of the other means of energy storage that we have today are simply not efficient enough. They can store some of the energy in some places; this is a good idea, but on a global basis this does not work. We have the full understanding of what we want to do, but we need to expand this enormously, and I hope I could give you a little glimpse into this – into how we can do this – that we convert the knowledge about steps and catalysts into technologies. This sounds easy, but it is not at all easy. There are many, many details to pay attention to when you want to actually do this in a laboratory.

But now comes your part. Our part is to deliver you some options. But, you, as the users of energy, also have to work on this. We have heard this several times. The energy challenge is not only a technological challenge; this is also a historic, behavioural or societal challenge. I just mentioned price and prejudice to you. You can start thinking about how expensive energy is, who pays the price and who determines what the price is. It is not the market. There are lots of other things behind the market determining the price. This is a very critical thing that you have to do, because I, as a chemist, can only give you options; but you have to decide how to use these options. You need to support the implementation of our options; we can only give them to you. I hope I was able to show you how we do this. We have made a lot of progress in the past, but we should not think that in a couple of years the issue will be solved. The issue has enormous dimensions, and it will take decades and generations to convert our entire energy system. But the starting point is here and now. We heard in the first talk that there was the Big Bang, and we have a similar Big Bang here and now in our energy system. We need to convert it here and today.

->Quelle: falling-walls.com/Robert+Schlögl