Carbon capture is a key component in U.S. energy strategy—but after the greenhouse gas has been captured, scientists are still working out what to do with it! One laboratory at the National Energy Technology Laboratory (NETL) has focused on using the captured carbon as a potential supply of industrially valuable chemicals and fuels.

The process the researchers are refining is known as electrochemical conversion—the application of electrical energy to one material to transform it into another. In the NETL lab, a very special form of gold—Au25—is being used to break the molecular bonds of CO2 and water and convert them into carbon monoxide and hydrogen.

Au25 is a nanoparticle with only 25 gold atoms. Nanoparticles are only slightly larger than individual atoms, measuring under 100 nanometers. The particles are so small, most microscopes can’t even see them! The structure of a nanoparticle can determine how stable—or unlikely to break down into smaller units—a particle is. Twenty-five gold atoms, it turns out, makes for a very stable particle. But more than that, the particle is particularly efficient at catalyzing CO2 conversion.

Chemical reactions are not always efficient; electrons can get lost in the process. Imagine a simple conversion we do every day—transforming money into groceries or gas. Now what if, during that process, your change started to go missing, lost between couch cushions or shortchanged at the till? Like pennies, electrons can disappear, and you won’t always get everything out of a system that you put into it. But AU25 doesn’t lose electrons.

The conversion process at NETL is unique in another way. A common challenge facing electrochemical conversion systems is the difficulty in choosing an energy source to power the reaction. Creating electricity requires energy, and if that energy comes from fossil fuel technology then the conversion process may actually create more carbon than it transforms. Researchers at NETL developed a way to bypass that hurdle by relying on solar cells to power the conversion. Consequentially, the system is actually carbon-negative—transforming CO2 without creating more!

The conversion technology is still being refined, and it may be many years until the research makes the jump from laboratory bench to commercial market, but for now—the future looks golden!