[Music] [Applause] so I'm going to tell you about how to make the world a better place with quantum mechanics but before I do that I need to start by thanking all the people who made the work that I'm about to show you possible science is collaborative and without my students here at St Lawrence and my collaborators around the country including Hines fry who first developed the materials I'm going to tell you about today and Katherine Jen in the physics department here at St Lawrence who helps me to understand those materials none of this would be possible so I'm going to tell you today about renewable energy and in particular why we need it and why I believe that a technology called artificial photosynthesis is the key to possibly the best form of renewable energy but let me start by telling you why we need artificial photosynthesis this is a chart of our planet's population and it's projected to continue growing over the next Century what's more most of those new people will be in the Nations that you see here in orange and red developing nations places where the standard of living is currently rising rapidly and so too is the demand for new energy now that's particularly a problem because of where we get our energy right now so of our current energy all of it comes from one of two sources either from deep within the planet things like radioactive elements or from sunlight now wait you might be saying I don't put sunlight in my car I put gasoline in my car I don't cook my food with sunlight unless you have a really big magnifying glass most of the energy that we're using at the moment comes in the form of fossil fuels materials like coal oil or gas now those materials Those comp complicated molecules that were burning they were once biological material they were once animals and plants and they got to be complicated molecules by the process of photosynthesis in essence when you use fossil fuels you are using our stored Bank of sunlight from long in the past but we don't want to use that stored bank for one it's finite we don't want to run out our trust funds so to speak but more problematically we've also found that using that stored sunlight makes permanent changes to our planet's climate so instead we need renewable energy sources some of these sources have been used by humans for centuries things like wind power or hydroelectric power well the hydro part anyway some of these Technologies are relatively new things like solar photovoltaics or geothermal power but all of these energy sources have their own challenges or drawbacks and most of those drawbacks come from how we distribute those resources how we capture that energy and then get it to people who need to use it in developed Nations like the United States we use an electrical grid to transmit energy that's generated from wind or solar or hydroelectric power that system of wires and Transformers carries electrical current from where it's generated to homes and businesses where we'll use it but renewable energy isn't quite as Cooperative as fossil fuels were sometimes the sun doesn't shine sometimes the wind doesn't blow and sometimes the waves don't crash so we need storage in our grid in order to properly use renewable fuels the problem with that is that for many people grids and grid storage are far too expensive for lots of those Nations that were colored in orange and red on that early figure it's just not a feasible option to build a large-scale grid so what we need is Renewable Power that is scalable to small sizes or large and affordable Now by comparison the chemical fuels things like oil and gas that we use today these sources work great they're energy dense they're relatively stable and there's current infrastructure to transport these resources from where they're created to where people use them if it weren't for the fact that they are finite and climate altering chemical fuels would be perfect so what we want are chemical fuels without all of the drawbacks that means we want to do what plants do take sunlight and transform that sunlight into an energy-dense chemical fuel photosynthesis is the name for that process plants take water and carbon dioxide and they turn it into compounds like sugar but plants have their own drawbacks for one they're not very efficient only about 1% of all the solar energy that reaches a plant gets turned into sugar and plants require arable land they need water they need fertile soil if we're devising a fuel source for the future we probably don't want it to require the same land that we need to feed those new people so we need something artificial we need a molecular machine that transforms carbon dioxide into fuel chemists would call that a catalyst shown here in blue a catalyst picks up reactant molecules binds them transforms them into product shown here in dream and then releases them so that it's ready to start the process again now to develop catalysts chemist use a three-step process we make them we test them and then we build theories to understand how they behave but to to explain that theory to you I'm going to have to teach you just a little bit of quantum mechanics don't worry I won't make you do any math so our planet is made up of matter that matter is made up of atoms and those atoms are made up of protons and electrons now quantum mechanics tells us that the way those protons and electrons are arranged determines the energy of a system and that only certain energy levels are allowed the electrons occupy these energy levels s when they move between those levels they do so by absorbing light to go up or emitting light to go down so if we can understand how light interacts with matter we can understand anything we want about that matter and we can make that artificial photosynthesis catalyst so what kind of catalyst do we want well we have to pick some elements right here's the periodic table a list of all of the elements that people know about and right in the middle shown in Gold here are six elements called the Platinum Group elements that are the MVPs of the periodic table the best medals for making catalysts but they're rare and they're expensive and if we're trying to make something that's scal aable and affordable something that everybody on the planet can use if we make it out of platinum that's probably not a great place to start so we need something made from more common stuff heterobimetallic chemistry let's break down that word hetero different to by metallic you guys get that one so shown here in yellow is zirconium and in blue is Cobalt and by combining together these two metals we can simulate the properties of those more expensive and rare Platinum Group Metals now how are we going to support these how are we going to put this Catalyst together to do that we use mesoporous Silica particles you can think of them a little bit like glass kitchen sponges they're microscopic and on the surface of those microscopic particles are nanometer wide pores down within those pores is where we bind the metals now photosynthesis light right these metals have to interact with light somehow have to harness that light and they harness that light by by picking up photons and using those photons to transfer an electron from the Cobalt to the zirconium let's zoom in on those Metals so shown here is a Cobalt and the zirconium at the start of this process everything is stable and happy Cobalt has seven electrons zirconium has none it turns out that's the way everything is that it's most stable when light interacts with this system the result is that an electron is moved pushed from the Cobalt to the zirconium resulting in what's called metal toetal charge transfer this state is unstable but it's also useful one of two things can happen once metal toetal charge transfer has occurred either that electron can go back to where it started through the process of back electron transfer and if that happens a little bit of light is emitted but we're not doing any photosynthesis on the other hand that electron can also go on to react with carbon dioxide transforming it into a much more reactive molecule so what we want to do is understand the way that that electron decides whether it wants to react or return but in order to understand that in order to test the properties of these materials we need to make them first and that's a three-step process now when we first synthesize this silica it's covered in junk basically in soap now some days I'm sure you felt like you're just sick of cleaning and the fastest way to be done with it would be just to burn it all down and start over that's what we do here we light these on fire to clean them off through a process called calcination we burn away all of that remaining material on the surface leaving it clean we then add in the zirconium but that zirconium doesn't come by itself the zirconium arrives with those two pentagonal rings of carbon atoms I want you to think of those like floaty wings that you might use to teach a child to swim they're making that zirconium stable and they're keeping it from binding to anything else on the surface but if that's the case we can't go any further while that carbon's there so what's the solution we're going to burn it again more calcination take away those carbon rings and just like a kid who in a pool who just lost their floaty wings that zirconium is pretty ready to grab on to the nearest thing it can find so we next add in Cobalt and the Cobalt binds preferentially next to the zirconium now when it does it brings along with it one more compound that nitrogen n there what we'll call an amine and I'll tell you about in just a moment so we made these things we say they might be good for renewable energy we probably should test that I'm a scientist that's what scientists do right we test things to do that we need an apparatus we need a way to both perform artificial photosynthesis and see what's going on so in collaboration with Katherine jeny here in the physics department we use this Raman spectroscopy apparatus to both blast our molecules with blue light that makes the artificial photosynthesis happen and then also probe what's happening when that photosynthesis occurs using green light so there's one thing I haven't talked about here just yet where do we make photosynthesis happen we need a place to mix together our Catalyst and carbon dioxide so we do that using a gas reaction cell in this case one that was made by one of my research students nikoleta cilia who graduated just this year from St Lawrence here she is in the physics department machine shop building her cell and here it is in action so on the top left you can see the Deep indigo color of the laser we use to actually perform the artificial photosynthesis in a practical device this laser would be replaced by sunlight we then probe the state of the system with the green light you can see in the bottom left and when we do that what do we find do these materials do artificial photosynthesis it's kind of a loaded question I wouldn't be here today if they don't so that bump you can see in the middle on the red line the line that shows what happens after our sample is exposed to Blue Light that line is the signature peak of what's called formic acid a molecule that looks a lot like carbon dioxide a molecule that comes from carbon dioxide but a molecule that is far more reactive than carbon dioxide so this is the first starting place that formic acid can be harvested and it can be transformed into much more complicated fuels but to do that we need to optimize this system we need need to be able to make that formic acid much more efficiently to do that we need to go back to Quantum Mechanics we need to think about energy levels again and we need to compare those two options back electron transfer where everything goes back to the way it started or the actual chemical reaction to do that we're going to use time resolved fluorescence so this work was done you can see by Alyssa Stone she's one of St Lawrence's liberal arts science Scholars and when she took this data what she was measuring was the effect of this overall process on the system in particular remember that nitrogen atom that was attached to the Cobalt by changing the structure of that compound and how it attaches we can control the energy levels of the Cobalt and in doing so we can control how much of the reaction goes towards the production of fuel versus how much goes towards back electron transfer and how quickly that happens so the results of that study are shown here how do you interpret this well the black line you can see is is the shape of our laser pulse what actually transferred the electron those lines decaying away from it are the back electron transfer processes and what you can see is that relative to the system by itself shown in green when we add in the amine and change its properties we can shift the line shown in purple so that back electron transfer happens more quickly in essence we can control the motion of electrons from one level to another we can get in there and manipulate artificial photosynthesis so in doing that we have here the first steps towards a molecular machine that can do what plants do without all of the drawbacks something that can take the positive aspects of renewable energy sources and combine them with the positive aspects of chemical fuels something that can be scalable and affordable and renewable that's the promise of artificial photosynthesis [Applause]