Publication Highlight

Electricity, Air, and Plastic Recycling

Daniel Morton — Tue, 17 Jun 2025 21:15:48 +0000

Electricity, Air, and Plastic Recycling Daniel Morton Tue, 06/17/2025 - 15:15

Daniel Morton

This collaboration between four RASEI Fellows shows how electricity can be used to impart ‘superoxide powers’ to oxygen gas molecules from air, enabling the efficient recycling of PET plastics.

In 2012, 32.5 million tons of plastic waste was produced globally. 4.5 million tons of which was poly(ethylene terephthalate), better known as PET. You likely know this as the plastic that has the number 1 in the middle of the recycling symbol. PET is used extensively in materials such as packaging, textiles, films, and flexible electronics. By far and away its main use is in bottled drinks. PET is considered a standout material, it is strong, chemically resistant, transparent, and impermeable to water. Even better, it is possible to recycle PET – it has its own number, right? Unfortunately, this is not quite the full story. Globally, it is estimated that only about 9% of plastic waste is recycled, and while PET waste is one of the best performers, with a recycling rate approaching between 25-30%, the majority of plastic, even PET, ultimately ends up in landfills, incinerated, or worse, polluting our environment. The magnitude of this problem is only increasing; in 2024 the world generated an estimated 240 million tons of plastic waste, representing more than eight-fold increase in 12 years and highlighting the need for more effective solutions.

This teams bring together four RASEI Fellows, Oana Luca (Chemistry, ɫ��Ƶ��), Seth Marder (Chemistry and Chemical & Biological Engineering, ɫ��Ƶ��), Stephen Barlow (RASEI, ɫ��Ƶ��) and Elisa Miller (Chemistry and Nanoscience, NREL) to address the accelerating issue of plastic waste. While there are many parts to this global challenge, this research focuses on how we recycle plastics, specifically PET. When we think about recycling plastic, most of us just think about throwing a plastic bottle, or piece of packaging, into a recycling bin. We rarely give it much thought after that. This really is just the start of a journey that is more complex than many realize. There are actually several different approaches to giving plastic a second life. The most common, and perhaps the method that most people are familiar with, is mechanical recycling.

Think of mechanical recycling like an industrial washing machine combined with a paper shredder. Plastic items are collected, sorted, cleaned, and then chopped up into small flakes or melted down into pellets that can be molded into new products. This approach is efficient and works great for clean, single-type plastics, but there are some significant limitations with this process. In the same way that a white shirt can’t be perfectly restored after being mixed with brightly colored laundry, plastic quality degrades each time it goes through mechanical recycling. This reduction in quality is stark, most mechanically recycled plastics can only go through the process 2-3 times before they become unusable. This makes it financially unattractive and severely limits the long-term efficacy of recycling. How can this be an enduring solution if we can only recycle something a couple of times?

Chemical recycling takes a very different route, instead of the ‘brute-force’ approach of just melting and reshaping the plastic, it employs a more surgical method, breaking down the plastic polymer chains into their constituent molecular building blocks. These molecular building blocks can then be used, either to make new plastics, or for other applications. Because the new plastics are made with molecular control, there is no degradation in quality, and the materials can be recycled over and over, essentially as many times as you wish. Instead of a washing machine combined with a paper shredder, this is more like a LEGO set, where the model can be taken apart brick by brick and be used to build something entirely new. This research describes a new approach to depolymerization, a class of chemical recycling.

The research described in this RASEI collaboration, just published in ACS Sustainable Chemistry and Engineering, offers a new, more efficient approach. By passing an electric charge through the reaction, electrons can be used to activate molecules that can then go on to react with the polymer. In a recent study, that used additive molecules as electron shuttles, the team observed the addition of electrons to oxygen gas molecules in small amounts present in the reaction, that were originally thought to be innocent bystanders in the mixture. This led the team to hypothesize that oxygen gas molecules, directly from air, could be chemically reduced, (that is that they take on an extra electron), leading to the formation of a relatively stable superoxide radical anion, O₂^·–. This activated superoxide now acts in place of the solvent and reacts directly with the polymer. Since the superoxide has an extra electron gained from the electric current, the negatively charged superoxide molecule reacts with the centers that have a positive charge on the polymer. This results in the breaking down of the polymer in a predictable and selective fashion, and the incorporation of oxygen into the building blocks instead of the solvent molecules, leading to the reliable and reproducible formation of the same molecules that were used to build the polymer in the first place. The LEGO bricks are formed cleanly and are ready to be used again, with no degradation in molecular quality. This work demonstrates this technology on a range of different plastics using air, arguably one of the most abundant and cheap reagents, as the primary oxygen source, and all done at room temperature and pressure, a huge improvement on other chemical recycling approaches. While the results are promising and show good efficiencies, this lab-based proof of principle still has a number of challenges to solve before it can be scaled up to meaningful levels.

Today, most plastics are recycled using mechanical recycling, which is like the combination of an industrial washing machine and a paper shredder, producing low-quality products and reducing the possibility of future recycling, leading many to explore chemical recycling as an alternative to gain access to more valuable chemical building blocks. Current mainstream chemical recycling methods are like using a sledgehammer, they typically require high temperatures and lots of energy to break the chemical bonds. The development of electrochemical methods offers a more controlled approach, breaking down plastics at the molecular level and reliably producing build blocks that can be used over and over again. New recycling technologies could transform how we handle plastic waste, opening the door to recycling previously un-recyclable plastics, doing it in a more energy efficient way, producing higher quality recycled plastics, and making recycling economically competitive with virgin plastic production from oil. The development of more effective and general recycling strategies isn’t just an environmental imperative. As plastic waste continues to accumulate, it is rapidly becoming an economic necessity. We already have so much plastic in the world, if we can develop methods to regenerate and reuse the building blocks from plastic waste it will turn landfills into gold mines.

How amazing would it be if instead of society wasting plastics, filling landfills, and polluting our environments, we viewed used plastics as a commodity for future applications?

June 2025

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Understanding light-driven production of hydrogen could unlock future insights for harnessing light for chemistry

Daniel Morton — Mon, 09 Jun 2025 16:27:04 +0000

Understanding light-driven production of hydrogen could unlock future insights for harnessing light for chemistry Daniel Morton Mon, 06/09/2025 - 10:27

Daniel Morton

Light to fuel: clean hydrogen production. Improved understanding of the light-driven production of hydrogen holds the promise not just to make the reaction more efficient in producing a fuel, but also to offer a framework to better understand future light-driven chemistries.

Many chemical reactions require the input of energy to activate the transformation. This can often be in the form of heat, or chemical energy. One of the most efficient ways of introducing energy into a reaction is by using light. If you don’t have to heat up a reaction, or add extra chemicals to it, and instead shine a light on it, you can save significant energy. However, it can be difficult to control and optimize light-driven reactions. This research, just published in Chem, is a collaboration between the Dukovic Group at the ɫ��Ƶ�� (ɫ��Ƶ��) and the King Group at the National Renewable Energy Lab (NREL) and provides a holistic understanding of the light-driven production of hydrogen gas using a nanocrystal-enzyme complex as the catalyst, and a computational framework that can be used more generally to understand other light-driven chemical reactions in the future. The code for this model is being made available in the supplementary documents of this article.

Chemical catalysis is a special type of reaction, one that increases the speed of a transformation and often reduces the amount of waste produced by the process. Think of it like an assembly line. The catalyst is like a station on the line, bringing together two or more components to create a new product that is then passed along. Without the catalyst the components might, by chance, bump together and form the desired product, but it will be much slower, and much less frequent. The catalyst remains unchanged in the process and can repeat the transformation many times.

Enzymes are Nature’s catalysts. On the cellular level, whenever a change needs to happen, an enzyme is usually involved. The speed of an enzyme, and its selectivity, that is its ability to only react with the desired molecules out of the soup of molecules present in a typical cell, is fantastic. Enzymes are often superior to catalysts we can make in a lab, and as such, much research has gone into finding ways to harness such enzymes to do reactions for us in the lab. Unfortunately, it is not as easy as just grabbing some enzyme out of a cell. Enzymes often require specific environments and partners to react with.

Redox enzymes are a special, and particularly attractive, class of enzymes. They are capable of adding, or removing, an electron from a chemical reaction, a key step in the production of hydrogen gas. Redox enzymes rarely exist by themselves. Returning to the assembly line analogy, to get a station that can add the electrons to the protons (H⁺) to make hydrogen gas, many other stations need to be added before in a specific order. In a cell there is a chain of enzymes that pass the electrons along before the reaction can take place.

This is where the artificial component comes in. The nanocrystal, which, when exposed to light, releases an electron, replaces the long chain of enzymes and can directly transfer an electron to the enzyme. So, you reduce your assembly line down from a chain of many stations to just two. “This work was really only possible through collaboration” explains Gordana Dukovic, the lead researcher at ɫ��Ƶ��. “The team at NREL have vast expertise in hydrogenase (the redox enzyme that creates hydrogen gas), and we have the expertise in making and tailoring the nanocrystals and studying what they do after they absorb light”. Getting the enzyme to work with the artificial electron donor took some work.

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This Research

Characterization of Photochemical Processes

Electron Transfer Kinetics

Competition between electron transfer processes

Activation Thermodynamics

Role of Surface-Capping Ligands

Quantum Efficiency of Charge Transfer

2020 Review of this research area

The two teams first started working together in 2011 and have invested a great deal of work in understanding many aspects of this nanocrystal-enzyme hybrid. “Working with the team at NREL has been really amazing” says Dukovic, “the opportunity to work with experts who really help you ask the important questions, and identify where our assumptions were wrong, was essential for this work.” For over more than a decade this collaboration has interrogated the different steps of this process, such as how the nanocrystal and enzyme fit together, how the nanocrystal generates an electron when exposed to light, how the nanocrystal transfers the electron to the enzyme, and how the enzyme uses those electrons to make hydrogen. It is only through building this comprehensive understanding of the steps that underpin this reaction that the team are in the position to provide a holistic picture of the whole transformation. Furthermore, the framework that they have built is robust enough to be applied in improving other light-driven reactions in the future.

This work describes an improved assembly line capable of converting light energy into hydrogen gas, a clean burning fuel that provides new, more efficient ways, to generate electricity. Perhaps more excitingly, it demonstrates the power of a new computational model and framework, built on over a decade of collaborative research, which has been made freely available, that provides insights into light-driven reactions and can be used by the scientific community to refine and optimize future light-driven chemistry. Helena Keller, the lead author is enthusiastic about the next steps “We are in a really exciting place now, where the capabilities of using computational methods to understand complex systems like this are becoming more and more accessible. The better we understand how to control processes at the smallest scales – like at the level of individual electron transfers – the closer we get to revolutionizing the way we produce energy and materials for the good of the world”.

June 2025

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Ocean microbes offer clues to environmental resilience

Daniel Morton — Fri, 16 May 2025 19:57:34 +0000

Ocean microbes offer clues to environmental resilience Daniel Morton Fri, 05/16/2025 - 13:57

May 2025

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Salt isn't just good for food, it improves perovskites solar harvesting properties as well

Daniel Morton — Thu, 01 May 2025 01:44:45 +0000

Salt isn't just good for food, it improves perovskites solar harvesting properties as well Daniel Morton Wed, 04/30/2025 - 19:44

April 2025

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An ultrafast microscope makes movies one femtosecond at a time

Daniel Morton — Tue, 11 Mar 2025 15:53:51 +0000

An ultrafast microscope makes movies one femtosecond at a time Daniel Morton Tue, 03/11/2025 - 09:53

March 2025

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Catalyzing the Sustainable Decomposition of PFAS Forever Chemicals

Daniel Morton — Sat, 21 Dec 2024 00:30:44 +0000

Catalyzing the Sustainable Decomposition of PFAS Forever Chemicals Daniel Morton Fri, 12/20/2024 - 17:30

Daniel Morton

RASEI Fellow Niels Damrauer is part of a collaborative team that have developed a new light-driven C-F activation reaction, one that has the potential to help dismantle PFAS ‘forever chemicals’

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Read the Article

Highlight in The Conversation

C&EN Highlight

Colorado Arts and Science Magazine Highlight

Perfluoroalkyl and polyfluoroalkyl substances, or PFAS, are synthetic compounds that have found widespread use in consumer products and industrial applications. Their water and grease resistant properties have been part of their attraction in their applications, but these are also the reason that they are now found practically everywhere in the environment, they are very difficult to decompose.

While many chemicals will decompose relatively quickly, studies have shown that PFAS are expected to stick around for up to 1000 years. While this durability is great in something like firefighting foams or non-stick cookware, it is not great when these compounds get into the environment.

This new article, published in Nature in November of 2024, describes the work of a collaborative team of theoretical and experimental chemists, who have developed a new photochemical reaction that could hold promise of speeding up the decomposition of PFAS. A recent highlight of this work, written by the graduate student and postdoctoral fellows who did the research, appeared in The Conversation.

Using a photocatalyst, that absorbs light to speed up a reaction, the researchers were able to ‘activate’ one of the carbon-fluorine bonds, one of the strongest bonds in organic chemistry. The photocatalyst absorbs light, transfers electrons to the fluorine containing molecules, which then breaks down the sturdy carbon-fluorine bond.

While this doesn’t decompose the whole molecule, it is essentially like finding a chink in the armor, it opens the door to degradation of the PFAS to harmless smaller molecules.

This study demonstrated this process on a small scale, and the researchers are looking at how to optimize this reaction so it is more robust and can be done on larger scales. This work is part of a National Science Foundation funded Center for Chemical Innovation called SuPRCat, a research community that will be looking at this challenge, among others.

If it is possible to break down these forever chemicals, it will help prevent these environmental pollutants being in our soil, rivers, and drinking water. Excited to see the next steps from the team!

December 2024

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RASEI Fellows Collaboration in CHOISE Twists Halide Perovskites From a Distance

Daniel Morton — Fri, 25 Oct 2024 22:31:11 +0000

RASEI Fellows Collaboration in CHOISE Twists Halide Perovskites From a Distance Daniel Morton Fri, 10/25/2024 - 16:31

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RASEI Researchers unlock a 'new synthetic frontier' for quantum dots

Daniel Morton — Thu, 24 Oct 2024 19:50:17 +0000

RASEI Researchers unlock a 'new synthetic frontier' for quantum dots Daniel Morton Thu, 10/24/2024 - 13:50

Lauren Scholz

Read the Full Paper here

University of Chicago Press Release

In a breakthrough for nanotechnology, researchers have discovered a new way to synthesize quantum dot nanocrystals using molten salt as a medium. Traditional methods to create these materials required organic solvents, which cannot withstand the high temperatures needed for certain semiconductor materials, particularly those combining elements from groups III and V on the periodic table. By using superheated molten sodium chloride, scientists were able to synthesize these semiconductor nanocrystals, paving the way for improved applications in fields like quantum computing, LED lighting, and solar technology.

Led by a team from the University of Chicago and collaborating institutions, including RASEI Fellows Sadegh Yazdi and Gordana Dukovic, this novel method also opens new avenues for materials science by enabling the synthesis of previously inaccessible nanocrystal compositions. The technique addresses long-standing challenges by providing a high-temperature environment without degrading the materials. Researchers hope this advance will contribute to new types of devices and materials, marking a significant expansion in the range of accessible quantum dot technologies.

For a more information, please see the press release from The University of Chicago.

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Discovery could lead to longer-lasting EV batteries, hasten energy transition

Anonymous — Thu, 12 Sep 2024 06:00:00 +0000

Discovery could lead to longer-lasting EV batteries, hasten energy transition Anonymous (not verified) Thu, 09/12/2024 - 00:00

Mike Toney explores how lithium-ion batteries self-discharge to improve future designs

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Probing intermediate configurations of oxygen evolution catalysis across the light spectrum

Anonymous — Mon, 09 Sep 2024 06:00:00 +0000

Probing intermediate configurations of oxygen evolution catalysis across the light spectrum Anonymous (not verified) Mon, 09/09/2024 - 00:00

Mapping a route for more efficient production of sustainable fuels

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Find out more about CEDARS

This perspective article, led by RASEI Fellow Tanja Cuk, brings together researchers at six research institutions from across the United States, to describe how advances in spectroscopy and theory can map out the elementary details of the oxygen evolution reaction, a critical reaction to enable the production of fuels from sustainable energy sources.

The oxygen evolution reaction (or OER for short), is a critical step in the creation of sustainable, decarbonized fuels, such as hydrogen. Water (H₂O) can be split into hydrogen (H₂) and oxygen (O₂) using electricity. This process pulls apart strong chemical bonds – it takes a lot of energy! If we can better understand this process, we can make it more efficient, which will enable us to create clean fuels and store renewable energy, like solar and wind power, to smooth out variations in the supply. Specifically, the OER is the half-reaction that occurs at the anode (positive electrode) during electrolysis, in which the water molecules are oxidized to produce oxygen gas (O₂), protons (H⁺), and electrons. Though this sounds straightforward, the process involves multiple intermediates, or steps, many of which are currently poorly defined. Understanding this complex process requires a collaborative approach. Jin Suntivich (Cornell University) and Dhananjay Kumar (North Carolina A&T) bring expertise in making advanced materials and electrochemistry, Geoffroy Hautier (Dartmouth College) and Ismaila Dabo (Carnegie Mellon University) develop theoretical models, and Ethan Crumlin (Lawrence Berkeley National Laboratory), Tanja Cuk (ɫ��Ƶ��), and Jin Suntivich use X-ray and optical spectroscopy to visualize the small molecular intermediates.

Imagine that you have to drive from Denver, Colorado, to Greensboro, North Carolina. If someone gave you a map that only showed your starting location and destination, it would be quite difficult. You would know that you had to head east, but you wouldn’t know what roads to take, which were the fastest moving, or where any good stops were along the way. You could probably get there, but you would get lost a few times on the way, use some of the slow roads, and maybe be stuck staying in places you didn’t want to. It would be a very inefficient journey. Now compare this to using a modern navigation app, one that has details of every road along the way, the speed limits, the traffic levels, where all the gas stations are, the good restaurants and coffee shops, and good places to stop for the night. You would be far more efficient (and happy) using the navigation app.

It is the same with a chemical reaction. If you understand the elementary steps of a reaction, you can design a system that is more efficient and effective at getting to the final product. Creating this ‘map’ for the OER is a central mission of the Center for Electrochemical Dynamics and Reactions on Surfaces (CEDARS). CEDARS is a Department of Energy funded Energy Frontier Research Center (EFRC), that brings together twelve research groups at five universities and two DOE national labs across the chemical, materials, and computational sciences. CEDARS is headed by Director Dhananjay Kumar at North Carolina A&T, with a strong program in thin materials research. This is the first EFRC awarded to an HBCU as a lead institution in the country. There are several challenges that need to be overcome before the OER process can be scaled up. Currently OER is expensive, energy intensive and not reliable for continuous long-term operation. OER requires large inputs of electricity, the catalysts used in the reaction are based on scarce materials that are unstable under long-term exposure to the harsh conditions present in the OER process. By better understanding the elementary steps of the OER reaction researchers can design cheaper, more efficient processes.

RASEI Fellow, and Associate Director of CEDARS Tanja Cuk explains that there have been a series of proposed oxygen-related intermediates (e.g. OH*, O*, O-O), but it has been hard to capture experimental evidence for them and the elementary steps that create them. “The article is a perspective on how to get at the intermediates and their dynamics within the buried electrode-electrolyte interface. The approach involves model crystalline materials, targeted spectroscopies to isolate the intermediates, and theoretical investigations that predict how they appear in the electrochemistry and the spectroscopy. We also use materials that bind the intermediates at different strengths, so that they appear statically and transiently.” This fundamental and basic energy sciences approach combines expertise from across CEDARS bringing together computational theoretical modeling, materials synthesis, and spectroscopy. The diversity of institutions involved has already provided for many student and postdoctoral exchanges that further deepen the background of the team and broaden the scope of the research. Just last month the Center Director and his graduate student visited NREL and CU to test the samples made at NCAT.

Precise control of the materials under investigation is required for effective characterization and theoretical modeling. Dhananjay Kumar, Jin Suntivich, and collaborators within CEDARS use a process called epitaxial layer deposition, a procedure where a thin crystalline layer is grown on top of a substrate. For these investigations the epitaxial layers are the OER catalysts made from ruthenium and titanium oxides that are then tested electrochemically. Geoffroy Hautier is a materials theorist who uses computational models to calculate the structure and defects that intermediates create in the materials and their impacts on x-ray and optical spectra. Ismaila Dabo takes these configurations and creates a model of the electrical and water environment around the electrode interface, describing a more realistic environment for the OER processes. To provide a more detailed understanding, the theoretical models are tested and refined based on feedback from advanced spectroscopic observations. The spectroscopies highlight static spectra of intermediate coverages and transient intermediates during OER. Jin Suntivich brings expertise in combining in-situ electrochemistry with non-linear optical techniques; Ethan Crumlin develops in-situ and time-resolved x-ray spectroscopies; Tanja Cuk combines in-situ electrochemistry with ultrafast optical spectroscopy. Integrating the computational advances with the experimental observations provides a powerful toolkit. Accurate interpretation of the spectral observations relies on the findings from the computational techniques.

While the ‘map’ for the OER has not been solved, this interdisciplinary and fundamental approach to interrogating the OER process is providing invaluable insights into how different catalysts bind to the intermediates and how this impacts different reaction pathways. By characterizing the nature of the intermediates bound to the catalyst an understanding of their equilibrium behavior during the OER process can be developed. The CEDARS team are already thinking about next steps for this powerful approach. These include understanding the non-equilibrium dynamics of these intermediates by fully time resolved x-ray and optical probes and investigating more complex material structures. The observations from these ‘in-process’ reactions will help define the roadmap to a more efficient and cost-effective approach to generate clean fuels from renewable energy sources.

NATURE ENERGY, 2024 | https://doi.org/10.1038/s41560-024-01583-x

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