Researchers at the University of California, San Diego, have shown that solar energy, with the help of catalysts, may be able to convert carbon dioxide into oxygen and carbon monoxide, which can then be used to make synthetic fuels.

Here’s how it would work: sunlight passes through carbon dioxide dissolved in a solution and is absorbed by a semiconductor photocathode, which converts the photons into electrons. The resulting current splits the carbon dioxide, much the way electricity can split water into hydrogen and oxygen. But in this case, the splitting is aided by two catalysts. One, at the cathode, helps produce carbon monoxide. The anode is made of platinum, which catalyzes the production of oxygen.

The prototype cathode, made from silicon, needed supplemental electricity to split the carbon dioxide. But the UCSD group is now experimenting with a gallium phosphide version (above, with circular metal contacts) that could run on sunlight alone.