The conversion at room temperature of gaseous carbon dioxide (CO2) into solid, carbon materials that could be used in energy storage, is demonstrated in a paper in Nature Communications this week. The research may have applications in the removal of CO2 from the atmosphere.

Negative carbon emission technologies are critical for ensuring a stable future climate. However, the gaseous state of CO2 complicates the indefinite storage of this greenhouse gas. Although much research has focused on reducing CO2 to high-value products (such as chemical feedstocks and fuel), these approaches do not permanently trap the carbon (indeed, fuels produced are simply burned).

Kourosh Kalantar-Zadeh, Torben Daeneke, Dorna Esrafilzadeh and colleagues developed a liquid-metal electrocatalyst that transforms gaseous CO2 directly into carbon-containing solids at room temperature. The liquid-metal catalyst, based on non-toxic gallium alloys, also prevents coking (solid carbon sticking onto the catalyst surface, which reduces catalytic activity). The authors then collected the solid and prepared supercapacitors, which may serve as lightweight battery materials in the future.

Unlike previous methods to prepare carbon nanomaterials, which often operate at temperatures of hundreds of degrees Celsius, the process demonstrated could help reduce the energy-intensive demands of CO2 conversion, the authors suggest. They argue that their method may result in a viable negative carbon emission technology.