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Fireside Chat – Carbon Dioxide Photo Reductive Yield – Daniel Lundberg

Summary
Daniel Lundberg, a Ph.D. candidate at MIT, and Dr. Andrew Jones at Activated Research Company discuss his research on using semiconductor nanoparticles to mimic photosynthesis and convert CO2 into renewable fuels and chemicals. He explains the challenges of analyzing formaldehyde as a product, and touches on potential applications for addressing methane emissions.

Topics

1.[00:00]Introduction

2.[01:25]Research Goals

3.[05:08]Synthetic Photosynthesis

4.[06:15]Background

5.[07:27]Challenges

6.[09:06]Nanoparticle Catalyst Materials

7.[10:42]Analytical Challenges

8.[12:32]Outstanding Questions

9.[15:46]Career Advice

10.[18:52]Other Topics

11.[21:19]Last Act

Introduction[00:00]

Hello everyone. I’m Andrew Jones, CEO of Activated Research Company, and I’m joined today by Daniel Lundberg, a Ph.D. candidate from MIT. Hi Daniel – thanks for coming.

Thanks for having me.

It’s great to have you here. It sounds like you’ve been doing some exciting work with carbon dioxide photo reduction and making renewable fuels and chemicals – something near and dear to my heart – so I’m excited to talk about your work, and to find out what got you into this area and where you see it going next.

Let’s talk about the paper you worked on under the direction of Michael Strano which is titled: Universal Kinetic Mechanism Describing CO2 Photoreductive Yield and Selectivity for Semiconducting Nanoparticle Photocatalysts. A lot of big words in there. Can you describe at a high level what you were trying to do, and what you were looking at?

Research Goals[01:25]

I guess it all starts with my lab at MIT – which is a pioneer and a founder of the field of what’s called Plant Nanobionics – which is the interface of living systems with nanotechnology synthetic systems which try to augment the capabilities of both.

We have a lot of natural systems – a lot of plants – in our lab and that was the inspiration. We want to make materials that are like plants, that have all these amazing properties. They can grow. They can strengthen. They can reinforce. They can sequester and incorporate the atmosphere which is, obviously, very important.

That’s the main background of the whole project. Can we make synthetic materials that have safe properties that are able to take say CO2 from the atmosphere, convert it under relatively ambient conditions with low partial temperatures, and produce monomeric units that can polymerize and grow into strengthening and reinforcing material systems.

We looked at it – and asked, “Has anyone really done anything like this?” There have been photosynthetic schemes proposed, but really nothing to make materials that actually grow.

We specifically looked at the literature for autocatalysis and found a huge divide. A group of people were performing these reactions and studying photocatalysts that are relatively active under extreme conditions – super high partial pressures of CO2, higher temperatures, very low pH ratio. On the other side, a group was performing very basic reactions with a lot of fuel scavengers and, sometimes, organic solvents. Both were incongruous to our vision of ambient conditions – just using what’s there – water, sunlight, and low concentrations of CO2.

We were kind of stuck. We didn’t know how to produce the molecule we wanted. We were aiming for formaldehyde as a reactive mimiet to then polymerize. After a review of the literature from what had been done at diverse, almost forced conditions, we found that others had been able to make the molecule we wanted to make – but they weren’t testing for it. Of, maybe, 300 reports we summarized – only 15% of them even mentioned formaldehyde as a product, but only 7% of them even attempted to test for it.

That’s due to a variety of issues. From an industrial viewpoint – it’s not relevant, as people don’t want it as a high value fuel like, say, methanol. From an analytical viewpoint – there are difficulties detecting the molecule. When people run these reactions – they sample gas with the GC, and they sample liquid with the GC – but if they don’t have the right analytical techniques, they won’t see any formaldehyde.

We knew it was an issue. We think formaldehyde is there. Others have reported it’s there. What tools do we need to detect it, to know it’s the one we want? How do we go about doing this? That’s how we came to use the Polyarc®, and advanced quantitative techniques, to really enable our research and enhance our results.

At a high level, you’re trying to mimic photosynthesis. I don’t know much about this on the biology side. You have a leaf that sucks in CO2, and it uses sunlight to then create sugars. That’s the photosynthetic process. You’re trying to do that synthetically with these nanoparticle catalysts. Is that right?

Synthetic Photosysnthesis[05:08]

Exactly. Just like plants. A leaf or pine needles or wherever there’s chlorophyll is a very complex chemical reactor. We want to take the reagents we have available to us in the atmosphere – CO2, water, and sunlight – and make something. We were humble in the fact that we were not going to try to make glucose. Obviously, natural systems are so complex. The joke I always make is that nature has had millions and millions of years to develop and fine-tune its systems – and I have to write a thesis in five years. Our goal was to use a simpler process – CO2 to a single carbon containing complex.

It looks like you were successful. You were able to bubble CO2 into a water solution with these catalysts – and you’re able to make chemicals, fuels, or building block formaldehydes from that.

Yeah.

That’s fantastic.

I know you’re a Minnesota guy just like me. How did you get into this field, and what motivated you to start working on this?

Background[06:15]

I’m from Minnesota, I grew up in the Twin Cities. My parents are from northern Minnesota and northern Wisconsin. Growing up, the best part of our summers, and our weekends – was getting out into nature. We’d go to state parks, Lake Superior, doing stuff outside: camping, fishing, skiing. That was one of the reasons I wanted to pursue Chemical Engineering as an undergrad.

Society has a lot of problems, and many of them are related to industrial production, or the use of chemicals or fuels. With all that going on – once I decided to go to grad school – I looked for a research lab that felt familiar to me. I wanted to work in nanotechnology, but had also been doing some cutting-edge work on what’s possible in the chemical space. Those interests led to the lab of Michael Strano to work on these materials.

Awesome. There’s a lot talk right now about sequestering CO2 and making materials, products, and fuels out of it. What do you think are the biggest challenges to doing that?

Challenges[07:27]

It’s definitely “all about the money.” It’s super expensive when you’re working with a dilute feedstock. It’s very difficult and very energy-intensive to accumulate the product, concentrate it, and then produce something from it.

CO2 sits in this thermodynamic well – where you can add energy to it and make literally anything you want to. Our perspective was – we’re not going to think about the industrial collection and conversion of CO2 from the atmosphere – we’re going to focus on: Can we make things? Can we add value to things that already exist?

When you paint a building, or coat a pipeline, we all know that synthetic materials have a limited lifetime. The reason they degrade is not because all of the material fails – it’s that small microcracks form and propagate until the underlying infrastructure is exposed to the elements. We synthesize, coat, scrape off, and recoat – over and over. If we could introduce a small growth rate or a pseudo incorporation – it wouldn’t take a lot of material to vastly extend the life of a material – and it would save on the cost and energy of making them in the first place.

Tell me more about these nanoparticle catalyst materials.

Nanoparticle Catalyst Materials[09:06]

There are a lot of ways you can use the sun’s energy and convert it into things. Photovoltaics will convert sunlight directly to electricity. We operate under the same principle. We have a semiconductor, we are a nanolab, so, of course, we have to use the nanoparticles which are very efficient for this process. They absorb sunlight, they make an exciton. An excited electron moves and leaves a hole behind. These particles will migrate to the surface of these small catalysts, and then the electron can reduce CO2. The hole can perform the other oxidative half reaction with water – assuming water is there to do water oxidation. That’s the scheme we use to do CO2 conversion.

I see.

Your paper includes a case for Titania with gold on top of it – are those the nanoparticles absorbing the light and creating the holes?

So, in our work the metal modifications were non-photonic, so it was just a semiconductor itself that was absorbing the light.

Okay, awesome.

You talked a bit about the analytical challenges of formaldehyde. That analysis is typically done with liquid chromatography and some difficult derivatization reactions. Did that hold back some of the research? What were the big analytical challenges you encountered?

Analytical Challenges[10:42]

Analyzing formaldehyde definitely held back the research. Everyone doing CO2 conversions uses gas chromatography to sample both the gas and the liquid. They don’t look for anything else. When you’re an undergrad doing the reaction, the easiest thing to do is to sample the gas. A common metric like the ratio of carbon monoxide produced to methane produced gives you a broad understanding of how reductive, and how active, your material is. You don’t care about CO. You don’t care about CH4.

We wanted liquid products with higher material values. If you have a GC and can quantify the carbon containing materials, you simply put the liquid in. If you don’t have a Polyarc® – you won’t see the formaldehyde. Most people don’t care. Methanol is a much higher value fuel. They just want to see what catalysts function, and whether they made methanol. We needed to analyze formaldehyde. We wanted to turn CO2 into tiny nanoparticles that mimicked plant-like systems – biological systems that can grow and strengthen. People just don’t care about what they can’t see. It’s easy to ignore.

And maybe some low-hanging fruit for you to pick off. I love that.

What questions still remain in this research? Where do you think it will go next?

Outstanding Questions[12:32]

There are several outstanding areas. We can detect formaldehyde as the product we want – but as you get greater conversion and greater CO2 reduction – selectivity begins to change and you realize it’s only a minor product. The most active material we saw had formaldehyde selectivity of under 1%. That’s a huge shift. The greatest formaldehyde activity ever for CO2 reduction was at roughly 80%. We’re making the product we want – but we need to do it faster and accumulate more of it.

We also found that the nanoparticles are really oxidative. You have an electron to CO2 reduction, but you also have a hole that could preferentially oxidize water. If you have carbon products in the system – like formaldehyde – the hole can also parasitically oxidize the species back to carbon monoxide or carbon dioxide – so we were almost spinning our wheels. We put energy in, and just cycled through the product we wanted. We’re now looking at chemical schemes to isolate, and accumulate, the reactive intermediate.

How far away are we from commercializing something like this – and being able to make our clothes with CO2?

We make our clothes with CO2 right now – this shirt is 100% cotton – so, certainly, there are great ways to use plants currently. For us, the major challenge is being able to accumulate the product at a rate that’s fast enough to actually use. We did some mathematical modeling and found that if we can increase the catalytic activity, or the amount of formaldehyde that we generate, by 10x – only one order of magnitude – we would be able to produce systems, or coatings, that on a mass for mass basis would incorporate and grow just as fast as plants do. That’s slow to the naked eye, but is certainly fast enough for plants that have decades, or even centuries, of life. For us, it was about accumulating formaldehyde at a faster rate. That’s what we’re working on at this point.

I love how this is bio-inspired – and now you’re using biology as a benchmark to measure your success. That’s great. You’re right, biology has had hundreds of millions of years to evolve, so you’ve done a lot in 5 years.

Yeah.

What Pros and Cons would you give other students who are looking to get into this field?

Career Advice[15:46]

If you can make it through school, can support yourself, and actually survive, it’s a huge Pro. In retrospect, I learned how to be a very good scientist at MIT. I made a lot of mistakes. I had a lot of difficulties over the last 2-4 years. I cannot stress enough the importance of continuing education in this field. With the challenges we face as a society – we need the best and the brightest minds, and, for me personally, I don’t think I could have made as big an impact with just an undergraduate degree.

You’re in your last year at MIT and will be moving on. What do you see happening next? What do you say to the next group of students coming in and taking over?

I’d like to encourage them. There are a lot of tracks – obviously, the science side, but maybe more importantly, the policy and legislation side. There’s a lot of money, a lot of time and effort, and a lot of smart people thinking about the same problems. It’s really a ripe space to work in – and there are super-pressing problems we can solve.

I love your approach of using sunlight. Do you think direct sunlight mechanisms will dominate the traditional approaches of Fischer-Tropsch, or methanolic gasoline, which requires a lot of hydrogen – which is going to come from a lot of electricity?

We looked at the smallest amount of potential energy required for CO2 reduction. In general, it’s not so steep – so direct photocatalytic systems that are taking the sun’s energy can certainly be more efficient than using a silicon photovoltaic, converting sunlight to electricity, and using that electricity to power some electrochemically driven process for CO2 reduction. There’s definitely potential to exceed that, but right now, most of the carbon the Earth is converting and cycling through is from living systems that are taking sunlight, so it’s definitely possible. It’s a promising space for a lot of carbon to be absorbed and sequestered.

Good point.

This is a great place to leave this. Is there anything I missed that you would like to talk about?

Other Topics[18:52]

We’re doing CO2 reduction, but we’re also doing a methane oxidation abatement as well. We’re trying to use the same system, but instead of using CO2 as a carbon source – we’re using methane. Both can be oxidized and reduced to formaldehyde. We’re still using a Polyarc® and trying to detect, and analyze, but instead of an uphill perspective for CO2 – methane needs a thermodynamically downhill perspective. It’s really easy to oxidize methane – and actually over-oxidize past formaldehyde as well.

It definitely wants to go all the way to CO2, doesn’t it?

Yeah, all the way.

So, you stop it at formaldehyde. I’m thinking landfills – but could this be used as a stranded methane source?

Definitely. Methane emission is a huge problem. It accounts for 20-30% of the warming happening this year. It’s a small gas by volume, and by concentration of the atmosphere, but it’s just so potent – any emission creates a lot of warming in a very short period of time.

We want to take the same idea – sequestering and converting greenhouse gases and using it to grow and strengthen materials. While CO2 is relatively abundant, methane emission is pretty concentrated. One of the sources we’re looking at now is pipe leakage – which accounts for roughly 3% of all methane released into the atmosphere. I live in Boston – and the infrastructure is very old and leaky. The methane leaking from small cracks has a high concentration – it’s almost like pure natural gas. By targeting the same materials to grow and strengthen materials – we can target and seal the cracks that are releasing the methane.

Okay. So, you could have a self-healing pipe so to speak. That sounds very promising.

Last Act[21:19]

Well, I look forward to following your work, and your Lab’s work under Michael Strano. This was fantastic. I learned something today – which is always a good thing.

Thank you, Daniel.

Thanks for having me, it was a wonderful conversation.

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