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Extreme Closeup of Copper Electrocatalysts in Action

Since the 1970s, scientists have known that copper has a special ability to transform CO2 into valuable chemicals and fuels. But for many years, scientists have struggled to understand how this common metal works as an electrocatalyst. Now, a research team has gained new insight by capturing real-time movies of copper nanoparticles 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,” said Peidong Yang, a UC Berkeley professor and senior faculty scientist at Berkeley Lab who led the study. “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 combined a new imaging technique—operando 4D electrochemical liquid-cell scanning transmission electron microscopy (STEM)—with resonant soft x-ray scattering (RSoXS) at Beamline 11.0.1.2 of the Advanced Light Source (ALS). First author Yao Yang, a UC Berkeley postdoctoral fellow, conceived the groundbreaking approach under the guidance of Peidong Yang while working toward his Ph.D. in chemistry at Cornell University. A special electrode custom-designed by co-author Cheng Wang, an ALS staff scientist, enabled the team to conduct x-ray experiments with an electrochemical liquid cell compatible with both STEM and x-ray instruments.

The STEM experiments enabled the researchers to record real-time movies of copper nanoparticles combining into larger metallic nanograins within a matter of seconds during CO2 electrolysis. 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. The findings have implications for “rationally designing efficient CO2 electrocatalysts,” Peidong Yang said.

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.

Inside a stylized electrochemical liquid cell, six copper nanoparticles (each one depicted as a ball composed of many copper-colored “atoms”) merge in steps (left to right) into one large, irregularly shaped nanograin as a green beam shines down from above.
Artist’s rendering of a copper nanoparticle as it evolves during CO2 electrolysis: Copper nanoparticles (left) combine into larger metallic copper “nanograins” (right) within seconds of the electrochemical reaction, reducing CO2 into new multicarbon products. (Credit: Yao Yang/Berkeley Lab.) Watch the 4D STEM video here.

Y. Yang, S. Louisia, S. Yu, J. Jin, I. Roh, C. Chen, M.V. Fonseca Guzman, J. Feijoo, P.-C. Chen, H. Wang, C.J. Pollock, X. Huang, Y.-T. Shao, C. Wang, D.A. Muller, H.D. Abruña, and P. Yang, “Operando studies reveal active Cu nanograins for CO2 electroreduction,” Nature 614, 262 (2023), doi:10.1038/s41586-022-05540-0.

Adapted from the Berkeley Lab news release, “How a Record-Breaking Copper Catalyst Converts CO2 Into Liquid Fuels.”