New approach makes one type of clean fuel production 66% more efficient

COLUMBUS, Ohio – Researchers have uncovered a more efficient way to turn carbon dioxide into methanol, a type of alcohol that can serve as a cleaner alternative fuel. 

In the lab, synthesizing methanol can be extremely difficult, due to the extremely complex reaction pathway needed to select for it. Previous attempts by the same team to manufacture this valuable liquid fuel from carbon dioxide have used a combination of cobalt phthalocyanine (CoPc) molecules and electricity, but this method is inefficient as only about 30% of the carbon dioxide is converted to methanol. 

To better scale up methanol production, the team in this study added a second material, nickel tetramethoxyphthalocyanine (NiPc-OCH3), to the nanotube catalyst where the reaction takes place. They discovered that adding this second molecule can catapult methanol production efficiency up to 50%, about 66% better than any other known process. 

“This catalyst system is one of the very few that can produce methanol at such high selectivity,” said Robert Baker, co-author of the study and a professor in chemistry and biochemistry at The Ohio State University.

Enhancing methanol production would not only allow scientists to make the liquid faster and more cheaply but also help them limit the amount of unwanted waste products. More importantly, having steady access to such a flexible renewable resource could transform many aspects of daily life, including the transportation sector, said Baker. 

“Methanol is a really desirable product for CO2 reduction because it has such a high energy density,” he said. “It’s a great molecule – of all the possible products of CO2 reduction, methanol is an excellent candidate for use as an alternative fuel.” 

The study was recently published in Nature Nanotechnology.

To confirm their findings, scientists used a technique called sum-frequency generation vibrational spectroscopy to analyze where carbon dioxide molecules were binding and how they were moving during their reaction. 

When carbon dioxide is introduced to NiPc-OCH3, researchers can see that it becomes carbon monoxide before the catalytic reaction turns it into methanol.  

In this case, the team saw that the carbon nanotubes, which held the two catalysts in place and helped electricity flow more smoothly through the reaction, influenced the carbon dioxide molecules’ movements. These tubes essentially act as a highway that ferries the reaction intermediates from one catalyst site to the next during this process.

“The dual nature of the nanotube catalysts causes the process to work extremely efficiently,” said Baker. 

Since this new process of methanol generation does require a large quantity of carbon dioxide, efforts to scale it up for commercial use would likely have to be used in tandem with carbon capture technologies that can remove harmful greenhouse gases from the atmosphere and sequester them elsewhere. “Capturing and converting carbon directly to a fuel would be one of humanity’s best possible options,” said Baker. 

What’s more, the understanding gained in this study about how creating dual catalysts from nanoscale building blocks can likely pave the way for other types of sustainable technologies, including opportunities for researchers to engineer brand new types of catalysts and chemical processes, said Baker. 

“Now we have the tools to understand how when you put different nanoscale components together in the right architectures, you can create new, more efficient systems,” he said. “It’s a really exciting time for this kind of research.”

The study was supported by the National Science Foundation and the Yale Center for Natural Carbon Capture. Co-authors include Quansong Zhu from Ohio State; Alvin Chang and Zhenxing Feng from Oregon State University; Huan Li, Zhan Jiang and Yongye Liang from the Southern University of Science and Technology; and Jing Li, Seonjeong Cheon, Yuanzuo Gao, Bo Shang, Conor L. Rooney, Longtao Ren, Shize Yang and Hailiang Wang, all from Yale University. 

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Contact: Robert Baker, Baker.2364@osu.edu

Written by: Tatyana Woodall, Woodall.52@osu.edu