Converting CO2 to Methane With Nanotubes

Penn State U. researchers have devised arrays of titania nanotubes to convert atmospheric CO2 to CH4 and other hydrocarbons using sunlight.

The rate of carbon dioxide (CO2) conversion using this method is 20 times higher than that of previously published research. The work is described in the January 27, 2009, online edition of Nano Letters.

....This type of solar-based conversion process only works if a photocatalyst—a material that reacts with light—is used to convert the CO2 into hydrocarbons. A photocatalyst that utilizes the most solar energy possible is the best option.

One popular photocatalyst candidate for the job has been titanium dioxide, also called titania, because it can powerfully react with oxygen. But so far, researchers haven't been able to make titania perform adequately despite experimenting with a variety of forms, such as nanoparticles, pellets, and multi-layer films.

Grimes and his colleagues used arrays of titania nanotubes. They created the nanotubes using a technique that incorporates nitrogen into the nanotubes' structures, which the researchers initially thought would help increase the conversion rate (this turned out to be true only in a very limited capacity).

The process also yields a high total surface area compared to other forms of the material, a property that aids in the conversion. To further boost the process, the group scattered an ultra-thin layer of platinum and/or copper "cocatalyst" nanoparticles on the surface of the array. _PO

Not only will this method produce useful hydrocarbon fuels, but if the global climate cools much further, such nano-arrays could be distributed across the globe to boost atmospheric methane levels -- to trap more of the suns heat, and stave off excessive global cooling. We would need to be careful not to allow methane concentrations to reach explosive levels, however. ;-)