21 Jan 2020

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“Green methane” from artificial photosynthesis could recycle CO2

CHICAGO, Jan. 13 (Xinhua) — A new artificial photosynthesis approach could use sunlight to turn carbon dioxide into methane, which could help make natural-gas-powered devices carbon neutral, according to a news release posted on the website of the University of Michigan (UM) on Friday.

Turning carbon dioxide into methane is a very difficult process, and the design of the catalyst is critical to the success of the reaction. The theoretical and computational work of UM researchers identified the key catalyst component: nanoparticles of copper and iron. The copper and iron hold onto molecules by their carbon and oxygen atoms, buying time for hydrogen to make the leap from the water molecule fragments onto the carbon atom.

The device is a sort of solar panel studded with nanoparticles of copper and iron. It can use the sun’s energy or an electrical current to break down the carbon dioxide and water.

The base layer is a silicon wafer, topped with nanowires, each 300 nanometers tall and about 30 nanometers wide, made of the semiconductor gallium nitride.

The arrangement creates a large surface area over which the reactions can occur. The nanoparticle-flecked nanowires are covered with a thin film of water.

The device can be designed to run under solar power alone, or the methane production can be amped up with a supplement of electricity. Alternatively, running on electricity, the device could potentially operate in the dark.

In practice, the artificial photosynthesis panel would need to be connected to a source of concentrated carbon dioxide, say carbon dioxide captured from industrial smokestacks. The device may also be configured to produce synthetic natural gas or formic acid, a common preservative in animal feed.

“Thirty percent of the energy in the U.S. comes from natural gas,” said Zetian Mi, UM professor of electrical engineering and computer science. “If we can generate green methane, it’s a big deal.”

UM holds multiple patents on this catalyst and is seeking partners to bring it to market. The researchers think that the solar-powered catalyst could be recycling smokestack carbon dioxide into clean-burning fuel within five to 10 years.

The findings have been published in Proceedings of the National Academy of Sciences.

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