 Thank you so much for coming here today. It's my pleasure to be here. I joined three months ago this wonderful community And I'm really happy and excited to be here, and I'm going to show you today a little bit of the Work that allow me to be here and In I'll try to give you a flavor of where I want my group to be in the next few years At least here at Stanford. So I want to start with Some Historical what I call historical analogies. So I put in this graph here the the pressure of a specific gas I'm not gonna tell you which gas In in the in the recent in the last few years, let's say and you see that the pressure of this gas increase increase Until today. So can you guess which gas this is? Well, I'm gonna tell you it's not co2. It's oxygen Turns out that this is a scale on the billions years and three billion years ago oxygen was started to being produced by some organisms and That started to do photosynthesis and initially oxygen dissolved into the oceans Cause changes to the rocks and so the concentration of oxygen stayed pretty low until it saturated and it Reached the concentration that we have today turns out that it's oxygen is really good for us But it was a dramatic cause a dramatic change to life on our planet when it started to being produced at that time So now we have in a different gas Which is also following a similar path because if we look at co2 in the last 400,000 years Years there have been some fluctuations And I'm not going to go into the details of the reason for that but in the last 200 years We clearly have an increase in the levels of co2 which are probably caused by the use of fossil fuels the the generation of energy through the use of fossil fuels and These levels of co2 have never seen before So we can create an analogy and say oxygen had dramatic Cause dramatic changes to the planet. What is co2 going to cause to to the planet? Maybe something similar. So we need to watch out for that and And So this this brings me to the second question for you We know that the levels of co2 rise because of the use of fossil fuels But we also know that this in these last 200 years that have there have been Tremendous improvements in the standards of living so we can take our car go out go where we want take our Plains and go to to Europe Have our houses cool in summer and and warm in winter So this This changes this use of fossil fuel really cause some some positive Improvements in our standards of living so my question is and this is the energy what I call the energy dilemma What should we choose for the future? So should we choose to go back to when we add less energy to favor a better environment? Because we know that this increase in co2 is causing dramatic changes to the environment or Or should we choose to keep our standards of living? So we still want to have our car We still want to have our house warm in winter, but we are going to get a worse environment in in the future This is the energy dilemma. Well, I hope I'll convince you by the end of this talk that maybe we don't need to choose we can still Still Still have the the the amounts of energy needed to drive our planet and also Leave in in a better environment environment than we have today However to get there that's the energy challenge We need to get there and so we need to be able to meet the the needs of the growing population and in particular the the Growing needs for oil and fossil fuel resources turns out that this is a picture from an American family 1970 with all the oil barrels that they used to consume per year. So that's the amount in 1970 and this is probably Twice and as much nowadays So we need to grow this this need to meet these needs and also be able to provide a better environment Because we want people for example in China or everywhere to be able to see the Sun with their eyes and We don't want them to need a screen to understand where the Sun is rising in in the morning and this this concept was very well described by the United Nations World Commission on Environment and Development Already almost 30 years ago when they define what sustainable development is which is the development That meets the needs of the present without compromising the ability of future generation to meet their own needs That's our energy challenge to meet sustainable development So that's my way to put this energy challenge. That's the way I compare this energy challenge. It's kind of a race between nature which is the turtle in this case and The hair which is us consuming fossil fuels at a pace at a rate which is That the nature is not able to keep up with so we need to find a way to speed up the turtle if we want nature to win this race and in some way we need to cheat and We need to make sure that nature is able to produce if we want or We need to replace this fossil fuel resources or find it a fuel that is replaced at a much faster pace than what's nature what nature usually does and What is that that science that deals with Increasing the rate of chemical reaction to produce fuels for example Eric introduced that before that's Catalysis catalysis is exactly the science of speeding up reactions And that's probably one of the things that we need here if we want the turtle to win the race and what is catalysis is represented very nicely here in this cartoon instead of Climbing this mountain which is the activation energy needed for molecules to overcome to be Transforming to the products we can take this this tunnel with using a specific call is that take us directly To to the products with a much lower activation energy. That's what catalysis is so The the idea here is that we need to develop better call is to Meet this this energy challenge. So how do we develop better call is I will use this this example the sentence that Gerard Hurtel and noble lecture in 2000 sorry noble prize in 2007 for his pioneering working catalysis used to say Talking about ammonia synthesis, which is one of the most important Discoveries of the 20th century. Well, if we read a sentence from his novel lecture He says large-scale technical production wouldn't off of ammonia in this case would not have been possible without the availability of a cheap call is this task could be solved successfully by Alvin Mitesh who in thousand of tests found that a material exhibited Satisfactory activity and I would point out this thousands of tests. That's exactly the way industry or even like academia in the 20th century used to Find new and better call is basically just trying try the trial that well known Trial and error procedure you try a bunch of materials and you see if it works or not clearly. That's not acceptable In the long term not just because we are wasting materials But also we because we need to solve our issues in a much more compelling way So that's my vision of how to get better call is to Tackle these energy challenges. It's divided into three areas The first one is controlled the second one is understand and the third of one is improved so nowadays we have with nanotechnology the tools to Precisely control the structure of material to the nanoscale and that's extremely important in catalysis because catalysis has always been a Nanotechnology discipline well before nanotechnology was even defined. So we have the control over these tiny crystals in the nanometer scale Once we have this control We can prepare a library of well of well-defined materials that we use to understand the catalytic reaction Mechanisms and we can draw what I call structure activity relationships here Then we can really understand where the the active sites are So we understand the active sites for their reaction Then we can go to the third task and we can Improve the catalytic activity of our materials but by increasing the density of these active sites once we know what what they are and eventually we can go back and Restart the loop and do it even better and that's In my opinion and much better way to find new and better call is that to increase the knowledge about catalytic systems for specific transformations that involve energy and the environment so during my Short talk today. I want to give you three examples of how to control understand and improve catalytic transformation that are taken from my PhD and postdoc research trying to Deliver these idea of how to use this well-defined materials to Understand and improve catalytic reactions that are very important for energy and environmental application So first of all, let me tell you What type of materials we are going to talk about today and these are supported systems It means that we have a small metal particle usually from the transition series and a support Which is high surface high specific surface area highly porous and the combination of metal and the support Which is usually a metal oxide in my case in this case gives rise to the callus Which we hope is extremely active and to give an idea here reported three electron microscopy images of supported systems where you have these arrows pointing to the small metal particles Surrounded by all the this high surface area material So you can understand you can have an idea of how complicated these things are with all these different facets These are all atoms and so on. So these are quite complicated and we want to Facilitate the studies on these materials and how do we do that by controlling? So we go to the first part of my talk how to control these materials to the nanoscale And it's been demonstrated in the last 10 to 15 years that colloidal methods I will talk about that later on as well can result in precise structures Under for for we can control structures In terms of many elements many properties. So for example in terms of size here We have metal nanocrystals of different sizes going from two nanometers here all the way to ten nanometers And these structures are so precise that we can control their their size down to atomic to the atomic scale so one particle differs from another More or less by one atomic layer only that's the level of control that we have nowadays But size control is not the only control that we have over these structures We can also control their shape so not just spherical particles But we can have elongated particles as reported here for this semiconductor nanorod, but we can also Control the composition which is extremely important in cathals. We can control the presence of defects that can also affect the catalytic activity, so we have a Very many knobs to turn in terms of control of the Structures that we can use to then prepare better catalysts And so I want to give an idea of how effective this control is for some Reactions, and I selected this reaction which is called methane steam reforming reaction It is quite simple you take methane and very important energy resource And you trade it with steam or water and you obtain CO and hydrogen and This mixture of CO and hydrogen is what we call industrially seen gas Or synthesis gas because it is used to make a variety of other compounds and this reaction is industrially Extremely important. It's run at very very large scale here reported some pictures of what we call steam reformers And you see the people here which gives you an idea of the scale of this reactor So industrially very important reaction as I said with that seeing as we can make a lot of other important things For example, it is used for ammonia synthesis and ammonia is extremely important to make fertilizers We can use it for methanol synthesis and methanol again It's a very versatile building block for polymers and a lot of other things or for higher alcohol Synthesis and in all these cases we need a specific ratio Between our hydrogen and CO coming out of this reaction Okay, so we need to be quite selective in that ratio and the way industry does that is by tuning This second reaction step, which is called water gas shift reaction in which they take a CO they treat it with an excess of steam and they can regulate the amount of CO2 and hydrogen so they can also Regulate the the CO2 hydrogen ratio here. Okay, so this is done in two steps So my point is can we control instead of controlling this in two step by controlling the nanostructure? So what we did was to prepare palladium nanoparticles nanocrystals palladium is one of the most active Metals for this reaction in different sizes are reported here electron microscopy images of these different sizes of palladium nanocrystal going from very small Let's say to larger it goes from around two nanometers about two nanometers to seven to eight nanometers so still a very very small range and Then we ran that reaction of methane steam reforming and here reported the selectivity towards CO Which basically gives an idea of that CO hydrogen ratio against the temperature and you see that by just changing the Size of the nanocrystals We're able to tune the selectivity of the CO to agent ratio that we can get out of this of this reaction And in particular we can go from very large from what I call very large particles from an agent to CO ratio of roughly three which will be good for example for Methanol synthesis we still need to tune it all the way to an agent CO ratio to roughly 12 Which means that we are approaching the ratios that are better for ammonia synthesis So they control over the nanostructure in one step clearly controls the selectivity for this reaction now I have to admit this is not extremely important for methane steam reforming because industrially it's one of the Most known reactions so we don't need to to work on that But this is just a proof of concept a demonstration of what control of the nanostructure can do for the selectivity of your reaction So if you want naively in the future, I can imagine instead of Well, this is it I'm an engineer so I shouldn't say that but instead of engineering all that that reactor I can engineer What goes into the reactor here and change the selectivity? The way I want that's where the future can be in terms of tailoring the nanostructures So now I want to come to the second part of my talk So we have the control over the nanostructures. What about understanding reaction mechanisms and so Here report the rate of one particular reaction We saw it before is the water gas shifts so CO plus water to give CO to an agent again industrially important reaction now if we run this reaction on the same metal same metal particle size But different supports that that orange is thing that I showed you before that is is used to support the particles Well, if we go from alumina to serum dioxide We can increase the reaction rate by hundred times just by changing the support Okay, and Syria serum dioxide in this case is well known to be a promoter for some reactions And it is well used in catalysis for example in three-way callus fuel cells Oxygen members and so on now what where is the origin of this? Improvement in the cavity activity provided by the support That's what we want to understand by controlling that the nanostructure So the idea was actually quite simple We have control over the the metal nanocrystals, so we take nanocrystals of different sizes We deposit them onto two different supports such as alumina and Syria with very different catalytic properties and we run our reactions of interest trying to draw those Diagrams that I call before structure activity relationships So I'm not gonna be talking about the alumina systems in interest of time But I will be focusing on the Syria supported systems So this is again the level of control that we can get in terms of composition and Size we can get platinum, palladium and nickel nanocrystals going from 1.6 nanometers to 12 nanometers And again these nanocrystals are very very similar in size Which means that the size distribution is very very narrow So one nanocrystal differs from the other by not more than one atomic layer And that's extremely important for what we are going to do with these nanocrystals So then we support these nanocrystals on Syria and then we study a Reaction which is reported here co oxidation and it's just the oxidation simply the oxidation of co to co2 Apparently simple, but the reason why we chose this reaction is because a we know it very very well because it's been studied for many decades and Second it's still an industrial important because co is a toxic gas It has to be eliminated in some way for example in the three-way catalyst in your car So it's still environmentally interesting to study this reaction. So now Here we have the activity of our nine samples I go back We have nine samples three platinum three palladium and three nickel with different sizes on Syria And this is the rate of the reaction of forced co oxidation against the temperature Reimbursed temperature now this graph is is pretty dense, but what we need to Consider here is just basically that the small nanocrystals Reported here with the with the red color perform better than the medium nanocrystals and better than the large nanocrystals Okay, this is the information that we get from this ground and it doesn't really matter actually what metal we are using Whether we are using the very expensive Platinum or the very cheap nickel as long as the particles are small now We want to understand why this happens and to do that we need to build physical models to correlate the structure of With the activity. We have the activity. We need a physical model for the structure So we did that by collaborating with Eric stock at Brookhaven National Lab. We did very accurate Transmission electron microscopy studies of our materials are reported here three representative Microscopy pictures of small medium and large palladium particles We use several of these to build our physical model in which we distinguish the The atoms in each nanocrystal depending on their position whether yet they are on the surface as reported here with the gray color or at the perimeter in contact with the support Which is reported here with this orange color or at the corner again in contact with the support as reported here in blue Okay, so now if we take this physical model very simple and we do just Very easy calculation. So this is theory We are still in the theory and we report the fraction of particular sites Which for us are the surface sites the perimeter sites or the corner sites against the diameter We obtain these three lines for the nine samples we had before this is against just theory just calculation now Because our samples are yes some kind of model samples because they are extremely controlled But we can put them inside a realistic reactor and test the The quality activity and the realistic condition We can also extract the calytic rate for these nine samples Which is reported here as turnover frequency at a specific at a specific temperature Basically just an indication of how many cycles per second This call is not able to to turn over in terms of their reaction So now if we get that number and we report it here We obtain this this black line here which lies in between The the model that we built for the corner sites and the model that we built for the perimeter sites This clear clearly tells us that the active sites are the ones at the perimeter and in contact with the support that's where our active sites are and What this means is that? Syria is such a good support and such a good promoter for this reaction because their reaction happens exactly at that Interface at that perimeter and by changing the nanocrystal size. We are able to change the the Fraction of atoms at that perimeter at that interface and so we are able to tune the Calytic activity of these systems. So now that we know that those Interface sites are the most active sites for the reaction We can go back to synthesis and prepare better call. It's based on this knowledge. So this is the idea of understanding after we control understanding the structures and Use that knowledge to prepare better systems this Leads me to the final part of my talk. So we saw how to control. We know how to control the structures we Understand many things in terms of the reaction mechanisms using this Very well-defined structures now. How do we improve? Calis based on that based on that knowledge and I want to do it Regarding one particular transformation, which is methane oxidation. So we know that methane is extremely important nowadays We have a lot of methane. It's a very good energy resource for many reasons What there is one problem with methane? it is an extremely powerful greenhouse gas and the emissions of an actually methane as a Is 8 to 72 times more harmful than CO2 in terms of greenhouse power So the emissions of methane and they are extremely Bad for the atmosphere for the environment So we have to limit those emissions and even in places where you know You think there there are no methane emissions because you don't see them if you scan this these images in under the IR light then you realize that there are a Huge emissions of methane close to for example oil drilling sites and so on but not only even in in case of diesel engines diesel trucks or Transportation there's the production of a lot of methane emissions that cause very important problems for the atmosphere so this is actually a huge issue and we know that not only CO2 in the last 400,000 years in the CO2 levels increased a lot, but especially with methane you see this is a vertical line So in the in the last hundreds years or so the the the methane levels rise by three times at least So this is a huge problem for the environment and it turns out that methane is an extremely stable molecule because those CH Bonds are extremely energetic and that's why it's a very good energy resource, but they are extremely hard to break So you need Materials that are extremely active to break down those those bonds and transform that into into CO2 and water Which is what we want to do so here. We don't really need to understand The requirements for their reaction because some other people did that for us So there are there there are a lot of studies on methane oxidation here reported one for example But we know that palladium oxide is the best Methan oxidation calories we have nowadays and especially when supported on Syria because of the reasons I told you before because of this interface effect that system is even more active So the point is now we understand what we need. How can we improve? How can we? Increase the density of those interfacial sides between palladium and Syria well our idea was to Build what we call core shell structures in which your palladium is at the core And you have a Syria shell and the interface between the metal and the support in this case is maximized So the number of interfacial sides here is maximized because the the Syria support is wrapping Around the nanoparticles so we developed this synthesis starting from pre for palladium particles all the way to these core shell structures This core shell structure are still colloidally stable because they are stabilized in organic solvents by this Not well-defined organic tails at least I don't want to enter into the details So we treat these as molecules so we can isolate this call this Core shell structure we can put them in a bottle we can spray them We can paint them and these still contain This core shell structure as kind of super molecules So what we could do with this was to take this super molecules Put them down onto a high surface area support and see how they Perform for the methane oxidation reaction, which is what we did So again, the reaction is kind of simple you take methane and you burn it with oxygen to to form co2 and water But the advantage is that co2 is much less harmful than methane in terms of emissions and greenhouse power So here reported the methane conversion against the temperature This is called light off curve for our core shell system here on the top Compared to two more conventional Calvist where your palladium is just sitting on top of either Syria or of alumina and with a mixture of Syria around and There are two important things to note from this from these light off curves here the first one is that the core shell structures deliver much better performance because if you see the temperature of Light off which is the temperature at which hundred percent of your methane is converted This is 400 degrees C for the core shell structure Calis and the other two systems are still well below 50% So the activity is much better as we would expect by increasing the density of these Interfacial sites the other very important and interesting thing is that if you take this temperature window Between 600 and 700 degrees C you have the thermodynamically favored decomposition of palladium oxide to metallic palladium and we know that palladium oxide is the active site is the active phase for this reaction so for example when you when you form Metallic palladium and you decompose palladium oxide to metallic palladium the activity decreases and only by increasing the temperature Then we are able to see an increase again in the activity Of these systems so this is found this characteristic and the composition of palladium oxide is found for any Single methane oxidation Calis based on palladium out in the literature now if we look at the core shell system There's nothing like that and the reason is because these core shell structures And the Syria in the shell is able to maintain palladium in its oxidized form Even up to very high temperatures and it doesn't allow that the composition of palladium oxide which means that the chemistry and the kinetics there are different and Not only we have a high activity for this system by engineering this active site But also this Syria shell forms some kind of a cage around the particle So the particles even at high temperatures don't move around too much And so the Calis turns out are also very stable So you can go up and down up to 850 degrees C and there's no decrease in activity or even do what we call a simulated aging So you keep your Calis at very high temperature for a long time and there is no decrease in activity So I hope I convinced you that by following these three steps control understand Improve we can get much better Calis than we have nowadays To tackle some of the big challenges that we have in energy and environmental applications And I didn't have the chance to go through other interesting projects that I did in the past related to this small molecules what I call small molecules met methane Hydrogen CO2, but I will be happy to talk and discuss with you about this eventually later during the reception so with this I want to thank the people that meant a lot to me in the past present and Hopefully will mean a lot to me in the future years Starting from my PhD advisor Palo for Nazir at the University of Trieste Ray Gordy also PhD advisor at University of Pennsylvania Chris Murray postdoc advisor and my my current fantastic group Thank you very much for listening and I'll be happy to take any questions Thank you again Anybody has any questions just Thank you very much for this very nice Summary of your research and those are the perspectives what it might do for the environment One question is regarding the stability of I mean there's catalytic performance, which you showed is very nice What is the material stability of the catalyst of the catalyst here entertaining right now in particular the question catalyst So it depends on the material that you use So if you're talking about the core shell systems, then we demonstrated that the stability is very good And the structures are maintained even up to very high temperatures as high as eight hundred and fifty degrees See if you are talking about this well-defined Nanocrystals then the stability might be an issue and we cannot go beyond five hundred degrees C If we want to do this structure activity relationship studies So it depends on the reaction that we are talking about and it depends on the material that we are dealing with and In that's that's the general consideration that we have to we have to make Very nice talk On the last part that you showed about the palladium and the Syria in a core shell structure I think you assemble them with some molecules Right if you go back to the picture yet some here, that's right and The mercaptor. Yes. Yes. This is a party I didn't have the chance to go right to the details Which means that the palladium particle and the in the Syria particles and not in contact or do you get rid of the molecules? Yeah, that's thank you. That's a very good question. So in interest of time I didn't have to go through the details, but I have a backup slide here So what we do we need to activate these materials for catalysis. So we need to remove all the organics Before we run our catalytic transfer before we run our catalytic reaction. So basically what we do with calcine So we expose these materials to up here to very high temperatures So all the organic byproducts are removed And then what we have to do is to make sure after we remove these ligands that we still maintain our structure And that's why we did Microscopy studies to make sure that that's that's that's true So what we have here is our alumina callus and with the arrows are the arrows are pointing to bright small dots and if we do what we call energy dispersive x-ray spectroscopy we can Find out that these bright dots are formed indeed by palladium and Serium so the palladium and serum are still there even after we remove all the all the ligands and everything And then if we do what we call a line profile scan We can see that the palladium signal comes from inside the Syria signal So we demonstrate that we still have the core shell structure that is in there then further we do I resolution transmission electron microscopy studies and we find out that we have this very small palladium core roughly 2 nanometers Surrounded not by a dense Syria shell, but a shell formed by small crystallites and so Here we have a model of how the The system is in which you have your small palladium particle and the shell is formed by these small Syria crystallized Surround in the palladium particle and so there is contact But there are also small pores here as you can see in some of the some of the images Where our reactants can come in be converted on to the palladium surface or palladium oxide surface and then Be Diffuse back into into the stream. Thanks for a very nice talk You you you show a very impressive control of of your your surface here by a special Set of synthesis techniques, how scalable are they? So if you don't want to make grams or I don't know how much you make probably on the grand scale But you want to make tons can can you scale up this? Yeah, that's so that's another important point Right now we are able to make Grounds of these materials in in the lab. So that's actually already a good starting point. So we are not limited to Micrograms of materials that can be made with other techniques The advantage if you one of this system is that we don't have injections or we don't have any Particularly difficult step during the reaction. It's just what we call a heat up procedure So there are actually companies that demonstrated that you can make maybe not tons of these materials, but definitely tens or hundreds of kilograms In in that sense. So there are for example companies in in Massachusetts working on somewhat related materials Quantum dots and that has been demonstrated to be scalable with with the same nice properties up to again hundreds of kilograms and some of these materials were introduced in in TVs and Some other devices. So it's it's not Hard to believe that this can make their way into the market Do you have some other questions? just more on the stability of the Syria shell so Syria is a It's a compound that Often undergoes oxygen exchange depending on the partial pressure of oxygen in the environment Have you ever done a study or maybe I'm sure there's studies out there about how that affects the stability of the Palladium or Whatever's in the core That's that's a very good question. Unfortunately, I don't have the backup slide But the the thermal treatments actually turn out to be extremely important for the reactivity of the systems and the chemistry of these structures is quite Quite different than conventional systems. So it turns out that when these Samples are calcined to too low temperatures and I mean 500 degrees C. The Syria is too reducible and It causes some deactivation issues that are not Permanent but still important and only when we increase the calcination temperature to Temperatures as high as 800 degrees C We're able to obtain something that is more stable and at that point we obtain something that is more similar to Conventional Syria in conventional high surface area Syria in terms of oxygen storage properties So there's a different chemistry going on into the system, which is which was one of the exciting things of this course as structures Maybe I missed it, but can you talk a little? I'm way back here. Yeah, sorry Can you talk a little bit about what the practical? Applications you see for this kind of a fabulous catalyst well There are practical applications we can we can use the the control Over the the nanostructures to improve for example the selectivity of specific processes or we can Use the compositional control over these structures to again improve selectivity and activity toward these processes because basically the idea is What if you can control these structures really down to the atomic scales, then you have very very well-defined active sites and If you know what these active sites are doing in terms of cattails, then you can control the the entire Calidic process so practical applications are in improving calories that we have today already by Increasing the density of the active sites that and we know what if we know what those active sites are or Make new calories for new processes by tuning the composition the the phase of these systems And by understanding how that affects the the the cali activity So I think the practical applications are several So we are not actually in that sense. We are not creating a new Cali-tic approach. We are just Controlling that much better to understand how to improve the cali-tic systems and we Prepare those cali-tic systems that are that show much much improved activities Any other questions? So let's thank with you one more time. Thank you. Thank you