Nanotechnology: scalable solutions for climate action

Welcome. This is the Sydney Ideas podcast, bringing you talks and conversations featuring the best and brightest minds at the University of Sydney, and beyond.

Good evening everyone. I'm Alice Motion. I'm from the School of Chemistry and the Interim Director of the Sydney Nano Institute here at the University of Sydney. So it's my great pleasure to welcome you this evening. I'm absolutely thrilled to be your host for our public event, 'Nanotechnology: scalable solutions for climate action', which is presented together with Sydney Ideas and Sydney Nano.

Before we start and I introduce you to our fabulous panel this evening – I would of course like to acknowledge the traditional owners of the land on which we meet this evening, the Gadigal people of the Eora nation. There is no place in Australia, water, land or air that has not been known, nurtured or loved by Aboriginal or Torres Strait Islander people. This always was and always will be, Aboriginal land.

So tonight's all about what nanoscience is doing to pave the way for new and better renewable technology. And I think just before we go into the nanoscience, just a little bit of a reminder of the scale that we're talking about here.

So we're talking about 10 to the minus nine – a billionth of a metre. So this is a strand of DNA, if you think about the diametre of that is about two and a half nanometers. But maybe something that we're a bit more familiar with, we think about a typical human hair. So it's really very, very tiny. And, ironically, to see things that are very tiny, we often need very big machines.

So tonight, we're going to be looking at what's happening in each of the areas, what the public may not know about some of these technologies, and what we need to do to implement them next because it takes a while to take research ideas that are being explored in a university setting, and to take them out into broader applications.

And we have three wonderful experts here who are working across all parts of the Sydney Nano community. They're also part of Faculty of Engineering, the Faculty of Science, and they're working in areas that span carbon removal, solar power and clean hydrogen.

And I'd like to introduce them to you now so I might start with the person furthest away from me. So Professor Deanna D'Alessandro is a chemist and a Professor at the Schools of Chemical and Biomolecular Engineering and Chemistry. So two schools and two faculties for Deanna. And she's also the Director of the Faculty of Engineering's Net Zero initiative. This is a really exciting new initiative at the university, which aims to help the government, industry and communities manufacture, deploy and adopt cost effective low emissions technologies at scale. Deanna has over 16 years of professional experience in material science. She's a passionate interdisciplinary scholar, and really wants to bring these interdisciplinary efforts together to address climate change through net zero and negative emissions technologies. Please welcome Deanna.

Next, I'd like to introduce you to Professor Francois Aguey-Zinsou, who is Professor of Chemistry at the University of Sydney, and he leads the MERLIN – so we've got something sounds like a wizard here – the 'Materials Energy Research Laboratory in Nanoscale' group at the School of Chemistry with over 20 years of experience, and he's one of the leading experts in hydrogen technology. So please join me in welcoming Francois.

And finally, immediately to my left is Professor Anita Ho-Baillie. Anita is the John Hooke Chair of Nanoscience here at the University of Sydney. She's also an ARC Future Fellow and an Adjunct Professor at the University of New South Wales. Anita's research interest is to engineer materials and devices at the nanoscale, to integrate solar cells into all kinds of surfaces to generate clean energy. Anita's a very highly cited researcher and has been identified as one of the leaders in advancing perovskite solar cells. We'll hear more about those later. Anita's achievements in setting solar cell efficiency world records in various categories have really placed her at the forefront of her research. So please welcome Anita.

But now, let's get started. And first of all, I would like to go to Anita – but I'm going to ask each member of our panel to take a moment to introduce yourself. I've given you a formal bio, but we'd like to know a little bit more about you and your role at the university. And we'd also really like to know, if you can put it as simply as possible, what is the technology that you're working on? So Anita, let's go to you.

So I'm working on the next generation solar technology. So the solar technology that we have on our roof or in the solar farm is based on silicon. So the solar cells within the panel is made of silicon. It's a fantastic technology, the cost of silicon solar cell has gone down by 10 times in the last 10 years, and really at the moment, is the cheapest renewable way of generating electricity. But it's got a limit to it. So the highest efficiency we can ever get – theoretically – is going to be 29%. So where does the 70% go? A lot of it's gone into heat and that's because silicon's got a limited way of absorbing the sunlight.

So we've got this thing called a band gap, and it limits the amount of energy the material can absorb. So you have sunlight with a photon energy that is spread across the spectrum. So for example, you have blue light, you have red light, you have green light, and you have orange light. So blue light is very energetic. And when silicon solar cells see the blue light, you absorb the sunlight. But because the photon is so energetic, a lot of the energy is wasted. So it turns into heat. So you have solar panels, that gets hot, and then you have light that is perhaps infrared. And the energy in the infrared light is actually lower than the bandgap of the silicon. So it just goes straight past the silicon solar cell and therefore doesn't get absorbed. So therefore, are we working on the next generation solar cell technology, where we engineer the materials to have different band gaps, so they are tailored to different Photon energy, and we stack them on top of each other. So we will have a blue cell, and then a green cell and an orange cell and the green cell and then a red cell. So we call this a multi junction solar cell. So silicon on our roof is single junction. And when we move on to double junction, then the efficiency will jump up to 40%. And when we move to trouble junction, the efficiency will jump up to 50%, and so on. So that's what we're working on. And we will talk about how nano comes into this technology.

And Anita is there a limit to the efficiency we can get with those solar cells?

Yes, so you can keep increasing the number of junctions. But as you increase the number, the improvement gets incremental. So it gets around 60% For six junction, but it gets very complicated after that. And of course, there's some fundamental limits to the solar cells. So you have losses that you can't quite get rid of because of thermal dynamics, because the sun is really hot. And your solar cell is not as hot. You have emission losses where you get the sunlight from a sort of narrow angle, but then it radiates back into broad angles. So you get those losses. So any solar cell is an absorber. And when you have an absorber, it always emits slides as well. So you get those losses you can't quite get rid of. But anyway, we're working towards hopefully 50% efficient solar cells. That's what we want to achieve.

Great. Well, we'll hear a little bit more about that in a moment. Thank you and Anita. So Francois, could you tell us a little bit about you and your role at the uni and your technology.

So a solar panel is great, but the sun is only shining during the day. And so you probably know that there are batteries around. But batteries don't have a very good energy density, which means that you cannot store a lot of energy. So best battery will you have today or lithium base, we are all using them. For example, in your mobile phone. They are good for running mobile phone good for running electrical bicycles and like light duty vehicles. But they are not very good for storing energy for long term. And for storing a lot of energy. And this is where hydrogen is very exciting. Because not only you can use renewable, but then you can convert that electricity into hydrogen. And hydrogen is something we can store, we can store around 4 million years and go to use that energy, again. And hydrogen is clean. So this means that we can substitute fossil fuels because fossil fuels not only provide energy, they also do a range of services. For example, we use them to make clothes we use it to make trucks, we use fossil fuel also to make chemicals. Hydrogen is also a precursor that we can use in the chemical industry, hydrogen is something we can also use to produce heat, the battery cannot produce it, for example, for some processes to make bricks, or to cook the best bread, whatever is a story. So really what we're working on in my lab is understand how we make hydrogen. And we also develop technology to store hydrogen as a form of a solid. So I'm sure all of you have heard about it. Hydrogen disaster, and all of you are probably scared of hydrogen. So what we are working on is storing hydrogen as a solid, not to compress gas anymore, but in material as a solid. So this makes the use of hydrogen safe because those materials store hydrogen within the structure. And they cannot simply resuse the hydrogen like this. And what we are working on also is developing a parent technology called fuel cells. And what we are interested in is enabling those technology, for example, to be 3d printed. So any of you can go to 3d print a fuel cell can go to 3d print an electriser, you don't need to be a scientist, like me or an engineer, and plug and play, you know, solar panels is nothing complicated to install on your roof, as long as you don't fall off. And that's the things that really excites me. So I should stop here. otherwise, I can talk forever.

Thank you, Francois Deanna, would you be able to share a little bit about yourself and your technology for us now?

Yeah, so look, I'm a chemist by trade. And I guess I've been fascinated with atoms and molecules most of my life. And I guess that really is the heart of why I work. Now with one of my hats on. One of my areas of work is applying the nanomaterials I make, which are called metal organic frameworks, or moss, for short. And these are highly porous materials that we'll get to a little bit later. But what's really exciting about these materials is that because of their incredible structural and physical properties, they have really interesting applications across a broad suite of areas. So one of the areas that we're going to talk about this evening is the area called direct air capture. And so what I mean by this is these materials can actually remove, in our case, greenhouse gases from the atmosphere, but they could be used to store hydrogen, they could be used as catalysts to convert one molecule into another molecule, they have actually been used in solar cells as well. And there are some close analogies between the structures of the materials I work on and the structures of the materials that Anita and Francois work on as well. So really, as a chemist, what excites me is the fact that we can design these materials, we can synthesize these materials, and we can do so in a way that makes them really highly tuned for the particular application. In our case, as I said, removing 0.04% of carbon dioxide from the atmosphere, which is this application called direct air capture that we'll talk about as we go on.

We might come back to you again, with question two, I would like to just open the question about how did you come to research this particular technology? What drives you to research this? And why should we as an audience who care about our climate, the future of our planet, the future of society, why should we care about your technology?

Well, I think the first thing to say is it didn't start with the technology. And I think this is the critical interplay between fundamentals and applied, actually, where it started was the discovery, not in my lab, but in labs around the world, one of the labs in America where I did my postdoctoral training, it was the discovery that we could, in fact, design and synthesize these materials, the development of the methodologies, if you like to selectively make these materials and make them in a way that they could, you know, be highly selective for particular gas molecules. It was actually that discovery that the fundamental discovery, if you like, that very much comes from just a desire to understand how atoms can be arranged in three dimensional space, it was actually that that really inspired the application. And then of course, you realize what you can actually do with these materials that are ultra high surface area materials, and we have some pictures a little bit later. And then of course, the potential of the application becomes apparent. And then you have this really close feedback loop between fundamental and application. And all of a sudden, you know, the world explodes with these materials as as we have as a scientific community.

Thanks, Deanna and for you Francois, why do you care about your technology? Why do you think it's important? Why should we?

I think the answer is quite simple. I'm born in Africa, in Benin. So this is not one of the richest countries on the planet. And as you probably know, if you don't have access to energy, simply to be able to read at night when you come back from school to be educated, then life becomes difficult. The thing about hydrogen is that you don't need to have access to fossil fuel. So if you're a country where you don't have fossil fuel reserves, you can produce hydrogen from anything from biomass, waste biomass that you may have organic food, or the leftover from your dinner, you can produce hydrogen from it also, you can produce hydrogen from renewable energy. And this is a thing that is very exciting for me this means that you can provide to people across the planet means to generate their own energy.

Thank you, Francois. And Anita, same question to you.

Right? So I've got two answers. The first one is, I guess, no doubt solar is going to be the future source of energy, because we want to move away our reliance on fossil fuels, because what carbon dioxide can do to our climates. But I'm also deeply inspired by solar. So when I was an undergraduate student, I never thought I will become a solid scientist. So I was going to be an electrical engineer. But one of our professors, he sneakily just put in some solar cell material in our electrical engineering circuit course. And he took us up to the roof of the building, and he show us a solar panel connected to a water pump. So he removed the cardboard, and you can see the water pump start pumping water, and the only way to stop it is to put the cardboard back on, and there's no power points. So when I saw that I was absolutely inspired. It's free energy from the sun. And after that, I remember in my first year PhD, we took our group of 15 undergraduate students to Nepal, where we installed our solar battery system for remote medical clinic that serve 30,000 people in the region. So just a simple solar battery system will give them lighting. So at night, if people like women in labour, they come into the clinic, they can see just simple things like that can improve people's lifestyle so much. And so the second highest uptake of solar is in a lot of third world countries still, where people are able to read at night simply having a solar system, a solar battery system allows women to read at night and children to read at night. And that's very valuable.

Thank you and Anita. So I think we have some images to help us understand a little bit more about your technology. So we'll start with you Anita. Can you explain to us a little bit more about the Nano component and how it works?

Sure. So I'll just step you through what we're looking at first. So on the right hand side is a little double junction tandem solar cell that we make in our lab, so sitting on the grass and is powering a little windmill. And on the left hand side is a schematic of what that double junction solar cell looks like. So you can see the grey thick slab and that's silicon. So that's the silicon solar cell that we all have. That's the incumbent technology on our roofs or in the solar farm. And then on top, we stack our perovskite solar cells, so perovskite is made of metal halide perovskite, it's a very good material, it absorbs light really, really well. And therefore we need a thin layer of it, to stack it on to the silicon. So where that nano component comes from, is in those yellow, and also blue layers, where we have to interconnect the perovskite cell, the top cell to the bottom silicon solar cell, also where the Nano component comes from a from the top of the solar cell, where you have the sunlight coming in, we can put nanoparticles there as well to steer the light into the solar cell. So when we get down to very, very, very small stuff, we found that the physics and the chemistry don't work necessarily classically. And we can make use of that to engineer the way the light works and also to engineer the electrons work. So we can engineer the way they go into the solar cell, and also engineer the electrons flow through the solar cell.

And how do you make those layers? What sort of techniques are you using in your lab to manufacture these nano impregnated layers?

Yeah, so now you know, actually, nanoparticles is not something new, really, I mean, gold nanoparticles have existed, you know, in centuries and you can see oh, wow, different size of gold nanoparticles will give you a different colour effects. The way we make them is by a physical deposition. So there are various way of depositing things onto something. So you can do it by solution. You can do it by spraying, you can do it by spreading you can do it by spinning. You can also inject energy into the particles so that it can go from one place to another. You can also like evaporate things. For example, if you heat up metal under low vacuum, it will have a high vapour pressure and therefore it can evaporate much easier than you would have in a normal atmosphere. So there's various ways of doing that. You can also do atomic layer deposition, where you can control the deposition at atomic scale.

So lots of different methods for making these layers. Thank you Anita. We're going to zoom in on Francois and his research now. So we're going from those sunny lawns at the University of Sydney, into understanding what's happening in these hydrogen focus laboratories. So Francois, take it away.

So, I'm not going to run through the entire slides. But typically, to come back to some of the technology we develop in installed hydrogen, we use material to do that. So here you have a range of material, LIBH4, MGH2, LANI5. And those material on this picture, they show you typically easy energy density, you have versus the output that a man or woman can deliver every day. So before we had all, we had slavery, right? So we don't necessarily want to go back there. So all gives you the equivalent of about 16 days of somebody doing work. And this is a machine doing that work now. So the question is, if we can develop the best battery that's about the work of 0.3, they have somebody working, so you can see that the best battery is not going to get us to go there to actually replace fossil fuels. Because fossil fuel can help us to do much more work than what we can do with a battery. If we look at one kilogram of hydrogen, this is equivalent to 49 days of somebody walking. So you can see that a lot of energy in hydrogen per kilogram. But the problem with hydrogen, it's a gas. So the energy per volume is very low. And this is why we use material to store this hydrogen so we can increase the amount of hydrogen we store per volume. Whereas the nano component comes in is that when a hydrogen comes to those material, in the form of applying hydrogen pressure, so material is tapped to circuit the hydrogen lattice sponge that you could put, for example, in a bucket of water, if you take a dry sponge, you put it in a bucket of water, the sponge will start to absorb the water, the material, here will do exactly the same, you put them under hydrogen pressure. So you put above the atmospheric pressure, those material under pressure, and they will start to soak up the hydrogen and store the hydrogen within their structure, whereas the nano comes is that when you start storing hydrogen within the structure, you want to do that under ambient conditions. So you don't need to have any energy input. And some of the material that can store much more hydrogen than long term nickel five year, which is 0.7 day of manwork equivalent, we would like to have a material at 7.4 day. So we can start to go to compete with oil. Zedd can only do that at relatively high temperature. So 400-500 degrees C, which is not ideal, because this means that you need to have another heat source. What we see in Kansas theory my group has been working on for for some time now is that if we actually make those material at very small scale, then exactly like what Anita mentioned, there's a rule of the chemistry and physics are different. And the way hydrogen interact with the structure is very different. And this means that we can start storing hydrogen at the ambiance in those material. And this is very exciting, because this means that we could develop technologies, where we could store a lot of hydrogen in a very safe way.

Thank you Francois. Deanna, over to you, let's have a closer look at some of the technology that your team and others are developing.

Thanks, Alice. So look, there's a little bit to unpack here. But at the heart of it is the nano. And so the little spinning picture that you see there is actually an atomic, it's actually an x ray crystal structure. And we get these structures by basically firing electrons at the material, and watching how the electrons deflect and diffract off the off the crystal planes. And so what we get out of that is this picture and every little sphere that you see there, the grey balls, the red balls, the blue balls, is an atom. And what you'll notice about the little spinning picture is that there are holes inside that particular material. And those holes are on the nanoscale. And what's particularly exciting here is that it's an ordered structure. It's a periodic structure. Actually perovskite is one structure type that can also be adopted by these metal organic frameworks. And it turns out that inside all of those little nano pores that's like a house in which can reside gas molecules or other guest molecules like liquids. And so basically what we're doing here as chemists is designing the atom placement. And by designing the atom placement, we can actually design how that material interacts with it. What we call adsorbent molecules like carbon dioxide or methane, or what we recognize as the greenhouse gases. And so that nano material is really right at the heart of one of the technologies I work on, which is direct air capture. And I didn't mention before that the reason why this is important is that we have 3 trillion tons of carbon dioxide in the atmosphere that was put there since the Industrial Age. And the latest Intergovernmental Panel on Climate Change report, just released a few weeks ago, shows us that to reach net zero, it's not going to be enough just to implement renewables and mitigate current emissions that actually, we also have to deal with the existing legacy emissions in our atmosphere. And so we need a portfolio of approaches. And this is just one of the options alongside the other technologies that we're talking about this evening. So you can see the correspondence here with solar because actually, the process that I work with my industry partner Southern Green Gas on is powered by solar. So right at the heart of you can see it looks a little bit like a two person tent, where the solar panels form the A frame. And underneath that A frame is where all the action happens. And so we have canisters that contain our metal organic framework sorbent, we use fans to draw in and this is now getting to the macro scale, but this is the interfacing of the nano with the macro. And those materials are very highly selective for carbon dioxide, they absorb the carbon dioxide, and hence we can remove carbon dioxide from air.

Thank you, Deanna. And we'll go back to you now. So my final question for each of you is that you've each shared some really exciting technology, some great nanoscience, I'd like to know a little bit more about what are the challenges for your technology now, and I'm thinking both on the technical side, but also on the social or the political side, what would jeopardize both technically, socially, politically, you being able to bring your technology into a place where we can use it and make sure that it's, it's holding true to its promise in trying to reduce, remove some of the impacts of carbon dioxide on our climate, so Deanna, for you first,

I think there's probably one word and that's scale. Because the scale of the problem is immense. We know that by the middle of this century, all of the modeling is showing us that we need to be removing something like 10 to 20 Giga tons of greenhouse gases from our atmosphere in order to have a hope of moving toward a netzero future. And so the scale of this is enormous. And it requires all hands on deck. And it requires that our technologies can come down the cost curve, because at the minute they are very costly. Making these nanomaterials on the scale that we need to make them is a challenge. So these are all the technical challenges of scaling. And then on the other side of it is the policy and legislative challenges. So for example, there is no policy nor legislation in New South Wales to actually use this technology. And the reason is that once we take the greenhouse gases out of the atmosphere, we need to durably put them somewhere, or do something with them. And at the moment, there is no legislation to enable us to do that there is in other states of Australia. So that gives you just a flavour of some of the challenges, not just at the nano scale, but actually also at the socio political and economic scale.

Thank you, Deanna, Francois.

Well, I can take this in different direction. I think I'm a dreamer. So, for me, I would like to see this technology that we are developing, being made free for all and the benefit of the community. Now, you may have heard a lot about hydrogen in recent years with a push toward setting up Australia to export hydrogen globally. I'm not sure we are there yet. I'm not sure by 2050, there will be a global market export. These are business as usual. For me, for me, the real challenge is we have climate change issue in front of us. And we need to accelerate how we develop technology and commercialize those technology and find the money for those technology to reach to the community and really understand how those technology could benefit to the community. So for me as I think it's a different agenda that is not necessarily understood. And this is where I would like to see some progress. Thank you, Francois, and Anita.

So for our technology being able to be as good as silicon in terms of the reliability, that's one challenge. silicate itself is quite good optical electronic material, but it's not the best. So with perovskite opto electronically, it's actually superb, but in terms of reliability solar panels, gotta last for 25 years' time now. And people may be even talking longer lifetime. So with perovskites, we need to stabilize it, we need to make sure that it doesn't degrade over a long period of time. And that's one of the challenges. Two years ago, we managed to stabilise the perovskite cell to pass three industry standards there for humidity and heat. And we will like to put more work in so that it's also stable under heat and light at the same time. So that's one of the technical challenges we've got.

And thank you all very much for joining us this evening. I'd like to welcome you to come to the next Sydney ideas event, which is on Monday, the 22nd of May. And I've just asked you to join with me in thanking Deanna Francois and Anita.

Thanks for listening to the Sydney ideas podcast. For more links resources or the transcript head to the Sydney ideas website or subscribe to Sydney ideas using your favourite podcast app.

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The speakers

Professor Kondo-Francois Aguey-Zinsou

Professor Deanna D’Alessandro

Professor Anita Ho-Baillie

Host: Associate Professor Alice Motion

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Nano revolution: taking health and medicine to the next level

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