A catalytic two-step: Transforming industrial CO2 into a renewable fuel

In a new study published in the journal Nature Nanotechnology, Yale chemist Hailiang Wang and his colleagues describe their latest breakthrough in creating methanol -- a widely used liquid fuel for internal combustion and other engines -- from industrial emissions of CO₂, a primary greenhouse gas contributing to climate change.

The process could have far-reaching applications throughout industry.

"This is a new strategy that brings CO₂ reduction into methanol to a new level," said Wang, a professor of chemistry in Yale's Faculty of Arts and Sciences and lead author of the new study. Wang is also a member of the Yale Energy Sciences Institute and the Yale Center for Natural Carbon Capture.

Transforming CO₂ into methanol is a two-step chemical reaction. First, CO₂ reacts with a catalyst to become carbon monoxide (CO). The CO then undergoes a catalytic reaction to become methanol.

The most effective previous process -- also developed in Wang's lab -- featured a single catalyst made of cobalt tetraaminophthalocyanine molecules supported on carbon nanotubes.

But the two reaction steps have a mismatch on this single-site catalyst: the conversion of CO2 to CO is not as efficient or selective, which presents a challenge for scientists trying to devise a robust process that can be scaled up for industrial use.

"Having just one type of catalytic site was not optimal for both steps in the reaction," said Jing Li, a postdoctoral associate in Wang's lab and first author of the new study. "To avoid this trade-off, we've now designed a 'two-in-one' catalyst."

The new process starts with a nickel tetramethoxyphthalocyanine site for the conversion of CO₂ into CO. The newly formed CO then migrates onto a cobalt site -- catalysis scientists refer to this as "spillover" -- to complete the reduction into methanol.

"Our work offers a potentially scalable solution to reduce carbon footprints and accelerate the transition to cleaner energy," said Conor Rooney, a former Ph.D. student in Wang's lab and co-author of the new study.

Rooney is a founder of Oxylus Energy, a company that works with industry partners to convert carbon waste into methanol liquid fuel, based on research from the Wang lab.

Additional co-authors from Yale include Seonjeong Cheon, Yuanzuo Gao, Bo Shang, Huan Li, Longtao Ren, and Shize Yang. Yang is director of Yale's aberration-corrected electron microscopy core facility, a comprehensive electron microscopy and spectroscopy lab focusing on materials science research.

The study is a collaboration with Quansong Zhu and Robert Baker of Ohio State University, who provided experimental evidence for CO spillover from the nickel site to the cobalt site. Other collaborators on the study include Alvin Chang and Zhenxing Feng of Oregon State University and Huan Li, Zhan Jiang, and Yongye Liang of Southern University of Science and Technology.

The research was funded, in part, by the Yale Center for Natural Carbon Capture and the National Science Foundation.