Scientists have captured the first-ever video of atoms in motion during a chemical reaction, revealing hidden pathways and short-lived molecules previously impossible to observe.
Using a new type of electron microscopy, the team watched a catalyst strip hydrogen atoms from alcohol molecules in real time. The discovery could revolutionize how we design greener and more efficient chemical processes, thanks to this unprecedented atomic-level view of catalysis in action.
First Glimpse of Catalysis in Action
For the first time, an international team led by Northwestern University has directly observed catalysis happening at the atomic level.
Using advanced imaging, the researchers captured mesmerizing real-time videos showing individual atoms moving during a chemical reaction that removes hydrogen atoms from an alcohol molecule. These recordings revealed short-lived intermediate molecules and uncovered a previously unknown reaction pathway.
The breakthrough was made possible by a cutting-edge technique called single-molecule atomic-resolution time-resolved electron microscopy (SMART-EM). This method allows scientists to watch individual molecules react as the process unfolds.
By seeing how atoms behave during catalysis, researchers gain a deeper understanding of how catalysts function. These insights could help design cleaner, more efficient chemical processes in the future.
The findings will be published on today, April 11, in the journal Chem.
This video shows a fleeting hemiacetal alkoxide intermediate, which the researchers, unprecedentedly, captured. The team also observed its reverse aldehyde elimination, generating an aldehyde and a molybdenum alkoxide intermediate. This transformation — the conversion of an alkoxy ether to an alkoxide — represents a textbook example of a thermal E1cB-elimination reaction, which is expected to proceed with a very low energy barrier. Credit: Northwestern University
Why Understanding Catalysts Matters
“By visualizing this process and following the reaction mechanisms, we can understand exactly what’s happening in the finest detail,” said Northwestern’s Yosi Kratish, the study’s first and co-corresponding author. “In the past, we haven’t been able to see how atoms move. Now we can. When I realized what we accomplished, I had to close my laptop and take a break for a few hours. Nobody has done this before in catalysis, so I was stunned.”
“Catalysts make modern life possible,” said Northwestern’s Tobin J. Marks, the study’s senior author. “They are used to make everything from fuel and fertilizers to plastics and medicines. To make chemical processes more efficient and environmentally friendly, we need to understand exactly how catalysts work at the atomic level. Our study is a big step toward achieving that.”
Scientists Behind the Breakthrough
A world-renowned expert in catalysis, Marks is the Charles E. and Emma H. Morrison Professor of Chemistry and Vladimir N. Ipatieff Professor of Catalytic Chemistry at Northwestern’s Weinberg College of Arts and Sciences and a professor of chemical and biological engineering at Northwestern’s McCormick School of Engineering. Kratish is a research assistant professor of chemistry in Marks’ group. Marks and Kratish co-led the study with Michael Bedzyk, professor of materials science and engineering at McCormick, and George C. Schatz, the Charles E. and Emma H. Morrison Professor of Chemistry at Weinberg, as well as the University of Tokyo’s Professor Eiichi Nakamura, who invented SMART-EM, and Assistant Professor Takayki Nakamuro.
Catching Fleeting Molecules with ‘Cinematic Chemistry’
Researchers long have sought to observe live catalytic events at the atomic level. Chemical reactions are like a journey between starting materials and the final product. Along the journey, transient — and sometimes unexpected — molecules form and then abruptly transform into other molecules. Because these so-called “intermediate” molecules are unpredictable and fleeting, they are difficult to detect.
By directly watching the reaction unfold, however, scientists can determine the exact sequence of events to reveal the complete reaction pathway — and view those elusive intermediates. But, until recently, it was impossible to observe these covert dynamics. While traditional electron microscopes can image atoms, their beams are too strong to image the soft, organic matter used in catalysis. The high-energy electrons easily break down carbon-based structures, destroying them before scientists can gather the data.
“Most conventional transmission electron microscopy techniques operate at conditions that easily damage organic molecules,” Kratish said. “This makes it extremely challenging to directly observe sensitive catalysts or organic matter during a reaction using traditional TEM methods.”
A New Way to Watch Reactions
To overcome this challenge, the team turned to SMART-EM, a novel technique that can capture images of delicate organic molecules. Unveiled by Nakamura and his team in 2018, SMART-EM uses a much lower electron dose, minimizing the amount of energy — and damage — transferred to the sample. By capturing rapid sequences of images, SMART-EM generates videos of dynamic processes, which Nakamura calls “cinematic chemistry.”
“Since 2007, physicists have been able to realize a dream over 200 years old — the ability to see an individual atom,” Nakamura said in a 2019 statement. “But it didn’t end there. Our research group has reached beyond this dream to create videos of molecules to see chemical reactions in unprecedented detail.”
Designing a Cleaner Experiment
When applying SMART-EM to catalysis for the first time, the Northwestern team chose a simple chemical reaction: removing hydrogen atoms from an alcohol molecule. But first they needed to select the right catalyst. About 85% of industrial catalysts are heterogeneous, meaning they are solid materials that react with liquids and gases. Although heterogeneous catalysts are stable and efficient, they are also messy, with many different surface sites where reactions might occur.
Zooming in on One Active Site
“Heterogeneous catalysts have many advantages,” Kratish said. “But there’s a major disadvantage: in many cases, they are a black box. They have an unknown number of sites where reactions can occur. So, we don’t fully understand where and how reactions take place. That means we cannot exactly figure out what part of the catalyst is most effective.”
To make the catalyst easier to study, the Northwestern team designed a single-site heterogeneous catalyst with a well-defined active site. The single-site catalyst comprised molybdenum oxide particles anchored to a cone-shaped carbon nanotube. Then, the team used SMART-EM to investigate how their catalyst facilitated the conversion of ethanol into hydrogen gas, a clean alternative to fossil fuels.
“Having a single site is a lot more convenient,” Kratish said. “We can pick a good site to monitor and really zoom into it.”
Revealing a Hidden Step in the Reaction
Before the study, scientists posited that alcohol went straight to the catalyst, where it became hydrogen gas and aldehyde (a molecule that forms when an alcohol molecule oxidizes). From there, the aldehyde, which is a gas at room temperature, escaped into the air. But watching the process unfold revealed a different story.
Using SMART-EM, the researchers discovered the aldehyde doesn’t float away but instead sticks to the catalyst. They also found the aldehydes linked together to form short-chain polymers — a previously unknown step that appeared to drive the overall reaction. In another surprise, the researchers discovered the aldehyde also reacts with alcohol to form hemiacetal, an intermediate molecule that is then converted into other products.
Confirming the Unexpected Chemistry
To confirm these findings, the team used various microscopy techniques, X-ray analysis, theoretical models, and computer simulations. All matched the SMART-EM data.
“This is a big breakthrough,” Kratish said. “SMART-EM is changing the way we look at chemistry. Eventually, we want to isolate those intermediates, control the amount of energy we put into the system, and study the kinetics of a live organic catalytic transformation. That will be phenomenal. This is just the beginning.”
Reference: “Atomic-resolution imaging as a mechanistic tool for studying single-site heterogeneous catalysis” 11 April 2025, Chem.
The study was supported by the U.S. Department of Energy. Marks is a member of the International Institute of Nanotechnology, Chemistry of Life Processes Institute, and Paula M. Trienens Institute for Sustainability and Energy.
