According to researchers at Penn State University, carbon dioxide emissions intensive industries could convert CO2 to a wide variety of hydrocarbons, such as methane. While methane is a powerful greenhouse gas, it’s a useful one that can be used for fuel.
The researchers state that while recycling of carbon dioxide into a high energy-content fuel is an attractive option, the process is energy intense and useful only if a renewable energy source can be used for the purpose – and solar energy appears to be the solution.
The "solar powered" carbon dioxide recycling system uses titanium dioxide nanotubes treated with nitrogen and coated with a thin layer of copper and platinum to convert a mixture of carbon dioxide and water vapour to methane.
Professor Craig A. Grimes and his team used natural sunlight to test their nanotubes in a chamber containing a mix of water vapor and carbon dioxide and 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 team found that using outdoor, visible light, a 20-times higher yield of methane could be achieved compared to previously published laboratory tests that use intense artificially generated ultraviolet exposures.
The chemical conversion of water and carbon dioxide to methane is seems relatively easy in theory – one carbon dioxide molecule and two water molecules become one methane molecule and two oxygen molecules. However, attempts have had very low conversion rates as the process requires an efficient photocatalyst that uses the maximum energy available in sunlight. The researchers are now working on converting their batch reactor into a continuous flow-through design that they believe will significantly increase yields.
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