Copper catalyst may be essential for production of solar fuels from sunlight, water, CO2
Staff Writer | February 23, 2023 |
Copper. (Image by James St. John, Flickr).
A research team led by Lawrence Berkeley National Laboratory has gained new insights into how copper works as an electrocatalyst, a mechanism that uses energy from electrons to chemically transform molecules into different products.
The new discoveries were done by capturing the real-time movements of copper nanoparticles, in other words, copper particles engineered at the scale of a billionth of a meter, as they convert CO2 and water into renewable fuels and chemicals: ethylene, ethanol, and propanol, among others.
“This is very exciting. After decades of work, we’re finally able to show—with undeniable proof—how copper electrocatalysts excel in CO2 reduction,” Peidong Yang, a senior faculty scientist in Berkeley Lab’s Materials Sciences and Chemical Sciences Divisions who led the study, said in a media statement. “Knowing how copper is such an excellent electrocatalyst brings us steps closer to turning CO2 into new, renewable solar fuels through artificial photosynthesis.”
The work was made possible by combining a new imaging technique called operando 4D electrochemical liquid-cell STEM (scanning transmission electron microscopy) with a soft X-ray probe to investigate the same sample environment: copper nanoparticles in liquid.
In a paper published in the journal Nature, Yang and his colleagues explain that during 4D-STEM experiments, they used a new electrochemical liquid cell to observe copper nanoparticles (ranging in size from 7 nanometers to 18 nanometers) evolve into active nanograins during CO2 electrolysis—a process that uses electricity to drive a reaction on the surface of an electrocatalyst.
The experiments revealed a surprise: copper nanoparticles combined into larger metallic copper “nanograins” within seconds of the electrochemical reaction.
Facilitating CO2 reduction
To learn more, the team turned to Cheng Wang, who pioneered a technique known as “resonant soft X-ray scattering (RSoXS) for soft materials.” With his help, they used the same electrochemical liquid cell but this time during the experiments to determine whether copper nanograins facilitate CO2 reduction.
Wang explained that soft X-rays are ideal for studying how copper electrocatalysts evolve during CO2 reduction.
The RSoXS experiments —along with additional evidence gathered at Cornell High Energy Synchrotron Source (CHESS)—proved that metallic copper nanograins serve as active sites for CO2 reduction. (Metallic copper, also known as copper(0), is a form of the element copper.)
Yang explained that during CO2 electrolysis, the copper nanoparticles change their structure during a process called “electrochemical scrambling.” The copper nanoparticles’ surface layer of oxide degrades, creating open sites on the copper surface for CO2 molecules to attach. And as CO2 “docks” or binds to the copper nanograin surface, electrons are then transferred to CO2, causing a reaction that simultaneously produces ethylene, ethanol, and propanol along with other multicarbon products.
“The copper nanograins essentially turn into little chemical manufacturing factories,” Yang said.
Further experiments revealed that size matters. All of the 7-nanometer copper nanoparticles participated in CO2 reduction, whereas the larger nanoparticles did not. In addition, the team learned that only metallic copper can efficiently reduce CO2 into multicarbon products.
In Yang’s view, these findings have implications for rationally designing efficient CO2 electrocatalysts.
The new study also validated his findings from 2017: That the 7-nanometer-sized copper nanoparticles require low inputs of energy to start CO2 reduction. As an electrocatalyst, the 7-nanometer copper nanoparticles required a record-low driving force that is about 300 millivolts less than typical bulk copper electrocatalysts.
This means that the copper nanograins could potentially boost the energy efficiency and productivity of some catalysts designed for artificial photosynthesis, a field of research that aims to produce fuels from sunlight, water, and CO2.
New Copper Catalyst Could Pave The Way For Next-Gen Solar Fuels
Lawrence Berkeley National Laboratory researchers have made real-time movies of copper nanoparticles as they evolve to convert carbon dioxide and water into renewable fuels and chemicals. Their new insights could help advance the next generation of solar fuels.
The paper about the research has been published in the journal Nature.
Since the 1970s, scientists have known that copper has a special ability to transform carbon dioxide into valuable chemicals and fuels. But for many years, scientists have struggled to understand how this common metal works as an electrocatalyst, a mechanism that uses energy from electrons to chemically transform molecules into different products.
Now, a research team led by Lawrence Berkeley National Laboratory (Berkeley Lab) has gained new insight by capturing real-time movies of copper nanoparticles (copper particles engineered at the scale of a billionth of a meter) as they convert CO2 and water into renewable fuels and chemicals: ethylene, ethanol, and propanol, among others. The work was reported in the journal Nature last week.
Peidong Yang, a senior faculty scientist in Berkeley Lab’s Materials Sciences and Chemical Sciences Divisions who led the study said, “This is very exciting. After decades of work, we’re finally able to show – with undeniable proof – how copper electrocatalysts excel in CO2 reduction.”
Yang is also a professor of chemistry and materials science and engineering at UC Berkeley. “Knowing how copper is such an excellent electrocatalyst brings us steps closer to turning CO2 into new, renewable solar fuels through artificial photosynthesis,” he added.
The work was made possible by combining a new imaging technique called operando 4D electrochemical liquid-cell STEM (scanning transmission electron microscopy) with a soft X-ray probe to investigate the same sample environment: copper nanoparticles in liquid.
First author Yao Yang, a UC Berkeley Miller postdoctoral fellow, conceived the groundbreaking approach under the guidance of Peidong Yang while working toward his Ph.D. in chemistry at Cornell University.
Scientists who study artificial photosynthesis materials and reactions have wanted to combine the power of an electron probe with X-rays, but the two techniques typically can’t be performed by the same instrument.
Electron microscopes (such as STEM or TEM) use beams of electrons and excel at characterizing the atomic structure in parts of a material. In recent years, 4D STEM (or “2D raster of 2D diffraction patterns using scanning transmission electron microscopy”) instruments, such as those at Berkeley Lab’s Molecular Foundry, have pushed the boundaries of electron microscopy even further, enabling scientists to map out atomic or molecular regions in a variety of materials, from hard metallic glass to soft, flexible films.
On the other hand, soft (or lower-energy) X-rays are useful for identifying and tracking chemical reactions in real time in an operando, or real-world, environment.
But now, scientists can have the best of both worlds. At the heart of the new technique is an electrochemical “liquid cell” sample holder with remarkable versatility. A thousand times thinner than a human hair, the device is compatible with both STEM and X-ray instruments.
The electrochemical liquid cell’s ultrathin design allows reliable imaging of delicate samples while protecting them from electron beam damage. A special electrode custom-designed by co-author Cheng Wang, a staff scientist at Berkeley Lab’s Advanced Light Source, enabled the team to conduct X-ray experiments with the electrochemical liquid cell. Combining the two allows researchers to comprehensively characterize electrochemical reactions in real time and at the nanoscale.
Getting granular
During 4D-STEM experiments, Yao Yang and the team used the new electrochemical liquid cell to observe copper nanoparticles (ranging in size from 7 nanometers to 18 nanometers) evolve into active nanograins during CO2 electrolysis – a process that uses electricity to drive a reaction on the surface of an electrocatalyst.
The experiments revealed a surprise: copper nanoparticles combined into larger metallic copper “nanograins” within seconds of the electrochemical reaction.
To learn more, the team turned to Wang, who pioneered a technique known as “resonant soft X-ray scattering (RSoXS) for soft materials,” at the Advanced Light Source more than 10 years ago.
With help from Wang, the research team used the same electrochemical liquid cell, but this time during RSoXS experiments, to determine whether copper nanograins facilitate CO2 reduction. Soft X-rays are ideal for studying how copper electrocatalysts evolve during CO2 reduction, Wang explained. By using RSoXS, researchers can monitor multiple reactions between thousands of nanoparticles in real time, and accurately identify chemical reactants and products.
The RSoXS experiments at the Advanced Light Source – along with additional evidence gathered at Cornell High Energy Synchrotron Source (CHESS) – proved that metallic copper nanograins serve as active sites for CO2 reduction. (Metallic copper, also known as copper(0), is a form of the element copper.)
During CO2 electrolysis, the copper nanoparticles change their structure during a process called “electrochemical scrambling.” The copper nanoparticles’ surface layer of oxide degrades, creating open sites on the copper surface for CO2 molecules to attach, explained Peidong Yang. And as CO2 “docks” or binds to the copper nanograin surface, electrons are then transferred to CO2, causing a reaction that simultaneously produces ethylene, ethanol, and propanol along with other multicarbon products.
Yang said, “The copper nanograins essentially turn into little chemical manufacturing factories.”
Further experiments at the Molecular Foundry, the Advanced Light Source, and CHESS revealed that size matters. All of the 7-nanometer copper nanoparticles participated in CO2 reduction, whereas the larger nanoparticles did not. In addition, the team learned that only metallic copper can efficiently reduce CO2 into multicarbon products. The findings have implications for “rationally designing efficient CO2 electrocatalysts,” Peidong Yang said.
The new study also validated Peidong Yang’s findings from 2017: That the 7-nanometer-sized copper nanoparticles require low inputs of energy to start CO2 reduction. As an electrocatalyst, the 7-nanometer copper nanoparticles required a record-low driving force that is about 300 millivolts less than typical bulk copper electrocatalysts. The best-performing catalysts that produce multicarbon products from CO2 typically operate at high driving force of 1 volt.
The copper nanograins could potentially boost the energy efficiency and productivity of some catalysts designed for artificial photosynthesis, a field of research that aims to produce solar fuels from sunlight, water, and CO2. Currently, researchers within the Department of Energy-funded Liquid Sunlight Alliance (LiSA) plan to use the copper nanograin catalysts in the design of future solar fuel devices.
“The technique’s ability to record real-time movies of a chemical process opens up exciting opportunities to study many other electrochemical energy conversion processes. It’s a huge breakthrough, and it would not have been possible without Yao and his pioneering work,” Peidong Yang said.
Researchers from Berkeley Lab, UC Berkeley, and Cornell University contributed to the work. Other authors on the paper include co-first authors Sheena Louisa and Sunmoon Yu, former UC Berkeley Ph.D. students in Peidong Yang’s group, along with Jianbo Jin, Inwhan Roh, Chubai Chen, Maria V. Fonseca Guzman, Julian Feijóo, Peng-Cheng Chen, Hongsen Wang, Christopher Pollock, Xin Huang, Yu-Tsuan Shao, Cheng Wang, David A. Muller, and Héctor D. Abruña.
Researchers from Berkeley Lab, UC Berkeley, and Cornell University contributed to the work. Other authors on the paper include co-first authors Sheena Louisa and Sunmoon Yu, former UC Berkeley Ph.D. students in Peidong Yang’s group, along with Jianbo Jin, Inwhan Roh, Chubai Chen, Maria V. Fonseca Guzman, Julian Feijóo, Peng-Cheng Chen, Hongsen Wang, Christopher Pollock, Xin Huang, Yu-Tsuan Shao, Cheng Wang, David A. Muller, and Héctor D. Abruña.
***
This is a really long press release, but is does a pretty good job of laying the relevant facts out sparing us most of the highly technical jargon. Its almost in a story format. Thanks are deserved and offered. Its really good news to see the future has a great deal of hope.
But.
This is recycling carbon in the form of CO2. That’s likely going to set off the anti-carbon extremist crowd. That’s just a pity. Driving to sustainability has to include carbon for life to exist. And CO2 is the active part of the earth’s and life’s carbon cycle. Hating on it seems so, well, choose your own term here.
Nature figured out CO2 is key for the planet to have life millions of years ago. We’re just at the cusp edge of catching up. Lets hope extremism doesn’t kill off natural progress used by technology.
By Brian Westenhaus via New Energy and Fuel
Active site identification and engineering during the dynamic evolution of copper-based catalysts for electrocatalytic CO2 reduction
Peer-Reviewed PublicationIMAGE: SCHEMATIC ILLUSTRATION OF THE TRIGGERS OF CATALYST RECONSTRUCTION, THE ACTIVE SITE THEORIES, AND THE CORRESPONDING TUNING STRATEGIES view more
CREDIT: ©SCIENCE CHINA PRESS
This review article is led by Prof. Fan Dong and associate research fellow Bangwei Deng (Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China). which was given to inspire more investigations and studies on the intrinsic active sites during the dynamic evolution of catalysts that could promote the optimization of the catalyst system to further improve the performance of CO2RR.
To date, copper-based catalysts are one of the most prominent catalysts that can electrochemically reduce CO2 towards high value fuels or chemicals, such as ethylene, ethanol, acetic acid. However, the chemically active feature of Cu-based catalysts hinders the understanding of the intrinsic catalytic active sites during the initial and the operative processes of CO2RR. The identification and engineering of active sites during the dynamic evolution of catalysts are thereby vital to further improve the activity, selectivity, and durability of Cu-based catalysts for high-performance CO2RR.
In this regard, four triggers for the dynamic evolution of catalysts were introduced in detail. Afterward, three typical active-site theories during the dynamic reconstruction of catalysts were discussed. In addition, the strategies in catalyst design were summarized according to the latest reports of Cu-based catalysts for CO2RR, including the tuning of electronic structure, controlling of the external potential, and regulation of local catalytic environment.
“The dynamic reconstruction of catalysts has now been well accepted by the research community, especially for Cu-based catalysts. Even though great advances have been achieved in the research of high performance CO2RR, however, the activity, selectivity, and durability for the industrial application of CO2RR on Cu-based catalysts are still unsatisfactory, particularly in the production of C2+ products. The detailed mechanisms on the intrinsic active site behind these dynamic properties, which are very important for the advanced catalyst design, are still ambiguous and more investigations are needed in future studies” Dong says.
Some perspectives are also given here to guide the future studies: 1) The triggers of the dynamic evolution of Cu-based catalysts should be carefully investigated, since several factors (intermediates, electrolyte, applied potential) are present along during CO2RR; 2) More factors such as such as the electrolytic cell type, mass/electron transfer, local electric field, pH variations, solution resistance, hydrophilic/hydrophobic feature of reaction interface, and supporting effects should be considered during the catalyst design; 3) High-throughput testing and machine learning are efficient techniques to further establish the structure–property relationship in more complicated conditions.
See the article:
Active site identification and engineering during the dynamic evolution of copper-based catalysts for electrocatalytic CO2 reduction https://link.springer.com/article/10.1007/s11426-022-1412-6
JOURNAL
Science China Chemistry
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