Berkeley researchers pin down how molten salts pull carbon from CO2

Operando spectroscopy caught a peroxide intermediate in molten-salt CO2 electrolysis, and the mechanism held across salts and electrodes.

Researchers at Lawrence Berkeley National Laboratory, UC Berkeley, and Estonia's National Institute of Chemical Physics and Biophysics have watched in real time how molten-salt electrolysis turns waste carbon dioxide into solid carbon. The process runs at 500°C using electricity and hot liquid salts, and the team found it proceeds in two steps rather than one, by way of a peroxide intermediate they identified with operando spectroelectrochemistry. The work appears in Nature Communications, first-authored by Sander Ratso.

The useful finding is the mechanism's stability. Changing the electrode materials and the molten salts left the basic reaction the same, which means the knobs that alter the structure of the carbon coming out can be turned without breaking the chemistry underneath. That is the difference between a reaction locked to one product and one that can be tuned toward several.

If it scales, it inverts a materials problem. Graphite is conventionally mined and refined; a route that builds carbon out of a waste stream instead turns a disposal cost into a feedstock and puts production wherever there is cheap electricity and a CO2 source. That substitution — manufacture what used to be extracted — is the pattern behind most inputs that got cheap.

It is early. Berkeley Lab's Mike Whittaker noted that wide deployment would want lower temperatures and cheaper salts than this, and the team still has to scale the approach to industrially useful quantities. This is a mechanism paper, not a plant.

Source: Phys.org