Carbon dioxide may soon be used to make fuel

Sunflower leaves
CC BY 2.0 Liz West

A newly developed, solar powered “leaf” mimics photosynthesis, converting CO2 into fuel.

Carbon dioxide is one of the main culprits of climate change, dramatically warming the Earth as it accumulates in the planet’s atmosphere. Fortunately, scientists have now found a new, beneficial use for carbon dioxide. As part of a new study from Argonne National Laboratory and the University of Illinois at Chicago, researchers developed an artificial leaf that uses solar power to transform CO2 into a fuel source.

The leaf mimics the process of photosynthesis that occurs naturally in plants. While plants use sunlight to convert carbon dioxide and water into glucose (sugar) and oxygen, the artificial leaf converts CO2 into syngas. Syngas, a mixture of carbon monoxide and hydrogen, is a fuel source with 50% of the energy density of natural gas. It can be converted into hydrocarbon fuels like diesel.

"In photosynthesis, trees need energy from light, water and carbon dioxide in order to make their fuel," explained Larry Curtiss, one of the authors of the study. "In our experiment, the ingredients are the same, but the product is different."

Carbon dioxide is not very chemically reactive, so the reactions that convert CO2 into burnable forms of carbon, known as reduction reactions, require a strong catalyst, a substance that speeds up the reaction rate. “On its own, it is quite difficult to convert carbon dioxide into something else," Curtiss noted.

The researchers couldn’t use the same catalysts that plants use during photosynthesis since the reactions are different. Instead, they utilized a compound known as tungsten diselenide (WSe2). WSe2 is about 1,000 times faster and 20 times cheaper than other common catalysts derived from gold or silver, and it lasts for over 100 hours, making it much more durable than many other catalysts used for reduction reactions.

This is not the first time that scientists have tried to convert carbon dioxide into fuel. Researchers at the USC Loker Hydrocarbon Research Institute previously developed a process for converting the CO2 from air into methanol. After bubbling air through an aqueous solution of a substance known as pentaethylenehexamine (PEHA) and adding a catalyst, the researchers heated the solution, ultimately converting 79% of the CO2 from the air into methanol, which could then be used for fuel.

Furthermore, last year, scientists at University of California, Berkeley developed a system that utilized nanowires and E. coli bacteria to convert CO2 into chemicals that could be used for biofuel. The process was also used to create biodegradable plastic and amorphadiene, which is a major component of anti-malaria drugs.

The process for carbon dioxide reduction that is utilized by the new artificial leaf is more efficient and less expensive than previous processes. “We burn so many different kinds of hydrocarbons — like coal, oil or gasoline — that finding an economical way to make chemical fuels more reusable with the help of sunlight might have a big impact,” explained Peter Zapol, one of the authors of the study. “Instead of producing energy in an unsustainable one-way route from fossil fuels to greenhouse gas, we can now reverse the process and recycle atmospheric carbon into fuel using sunlight,” Amin Salehi-Khojin, another author of the study, explained.

If the process proves to be cost effective, fuel created from CO2 may become a major source of energy. Combined with other renewable energy sources like wind power, this solar powered leaf could render fossil fuels obsolete.

Carbon dioxide may soon be used to make fuel
A newly developed, solar powered “leaf” mimics photosynthesis, converting CO2 into fuel.

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