The headline claims: Sunlight turns carbon dioxide to methane. Of course it does, plants do it all the time, but this uses a different technology.

The chemical conversion of water and carbon dioxide to methane is simple on paper -- one carbon dioxide molecule and two water molecules become one methane molecule and two oxygen molecules. However, for the reaction to occur, at least eight photons are required for each molecule. . .

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. . .

The researchers are now working on converting their batch reactor into a continuous flow-through design that they believe will significantly increase yields.

The researchers have filed a provisional patent on this work.

This is a long way from commercial application, but highlights one of the many efforts to develop hydrocarbon synthesis systems, and the slow but encouraging progress being made. Like many other efforts, nanotech methods are being used. This isn't grey goo nanotech - nanomachines in the SF sense - it's more of a next phase in materials science.