Solar power may be used to turn CO2 to methane

March 7th, 2009 - 5:19 pm ICT by ANI  

Washington, March 6 (ANI): A new study by Penn State University researchers has determined that dual catalysts may be the key to efficiently turning carbon dioxide (CO2) and water vapor into methane and other hydrocarbons using titania nanotubes and solar power.

Burning fossil fuels like oil, gas and coal release large amounts of CO2, a greenhouse gas, into the atmosphere.

Rather than contribute to global climate change, producers could convert CO2 to a wide variety of hydrocarbons, but this makes sense to do only when using solar energy.

Recycling of carbon dioxide via conversion into a high energy-content fuel, suitable for use in the existing hydrocarbon-based energy infrastructure, is an attractive option, however the process is energy intense and useful only if a renewable energy source can be used for the purpose, according to the researchers.

Craig A. Grimes, professor of electrical engineering at Penn State, and his team, used titanium dioxide nanotubes doped with nitrogen and coated with a thin layer of both copper and platinum to convert a mixture of carbon dioxide and water vapor to methane.

Using outdoor, visible light, they reported a 20-times higher yield of methane than previously published attempts conducted in laboratory conditions using intense ultraviolet exposures.

Converting carbon dioxide and water to methane using photocatalysis is an appealing idea, but historically, attempts have had very low conversion rates, said Grimes.

To get significant hydrocarbon reaction yields, requires an efficient photocatalyst that uses the maximum energy available in sunlight, he added.

The team used natural sunlight to test their nanotubes in a chamber containing a mix of water vapor and CO2.

They exposed the co-catalyst sensitized nanotubes to sunlight for 2.5 to 3.5 hours when the sun produced between 102 and 75 milliwatts for each square centimeter exposed.

The researchers found that nanotubes annealed at 600 degrees Celsius and coated with copper yielded the highest amounts of hydrocarbons and that the same nanotubes coated with platinum actually yielded more hydrogen, while the copper coated nanotubes produced more carbon monoxide.

When the team used a nanotube array with about half the surface coated in copper and the other half in platinum, they enhanced the hydrocarbon production and eliminated carbon monoxide.

The yield for these dual catalyst nanotubes was 163 parts per million hydrocarbons an hour for each square centimeter.

The yield from titania nanotubes without either copper or platinum catalysts is only about 10 parts per million.

If we uniformly coated the surface of the nanotube arrays with copper oxide, I think we could greatly improve the yield, said Grimes. (ANI)

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