Pulling Graphite Out of Thin Air

Graphite, a key ingredient in everyday items like #2 pencils, batteries, smartphones, laptops, and industrial equipment, is typically mined and processed. Currently, nearly the entire supply of this vital material is imported from other countries. However, researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), UC Berkeley, and Estonia's National Institute of Chemical Physics and Biophysics have discovered a promising method to create graphite by converting waste carbon drawn from the atmosphere.

Their findings, published in the journal Nature Communications, could potentially provide an alternative to mining. The team designed a custom microscope setup to observe a process called molten-salt electrolysis, which employs electricity and hot liquid salts to transform carbon dioxide into solid carbon. For the first time, they were able to watch this process in real-time within the corrosive, 500-degree-Celsius molten salts while the system was operational.

This observation answered a long-standing question about the molecular-level reaction mechanism, revealing an unexpected two-step process. Furthermore, the researchers determined that the chemical reaction remained consistent even when they altered the materials used for the electrodes and molten salts. This means that scientists could potentially manipulate the process to produce valuable carbon products, with the ultimate goal of generating battery-grade graphite.

Mike Whittaker, a scientist at Berkeley Lab, remarked, "This is a major win in a larger effort of synthesizing critical materials and battery materials using molten salts." If the process could be carried out at low temperatures using inexpensive salts, it could potentially be deployed in numerous locations, generating sufficient graphite to meet the demands of battery supply chains.

The researchers' approach illustrates a powerful new method to study chemistry within molten salts, a typically challenging environment due to its extreme conditions. The next step involves identifying the ideal combinations of molten salts, electrode materials, temperatures, and voltages to produce graphite and other carbon materials.

Researchers will also need to scale up the method to generate industrially useful quantities of carbon. This research was part of the MINerals for Energy Storage Synthesis (MINES) program, funded by the Department of Energy's Basic Energy Sciences program. Berkeley Lab, committed to groundbreaking research focused on discovery science and solutions for abundant and reliable energy supplies, is home to scientific facilities that enable groundbreaking work across various disciplines.