en.Wedoany.com Reported - Researchers at Lawrence Berkeley National Laboratory, in collaboration with UC Berkeley and Estonia's National Institute of Chemical Physics and Biophysics, have observed in real time the complete process of carbon dioxide transforming into solid carbon in molten salt at 500°C (932°F). The findings were published in the journal Nature Communications.
The technology is based on the principle of molten salt electrolysis. Liquid salt maintained at high temperatures conducts electricity between two electrodes, and when carbon dioxide enters the molten salt, the electric current strips away its oxygen atoms, with the reduction reaction depositing pure solid carbon on the cathode. Previously, observing this process at the molecular scale was nearly impossible because hot liquid salt is highly corrosive and rapidly destroys standard laboratory optics. To address this, the research team designed a specialized reaction cell equipped with heat-resistant lenses, enabling a custom microscope to continuously capture visual data at 500°C while the cell was in operation.
The real-time footage revealed that the chemical transformation occurs in two distinct stages. Carbon dioxide does not convert directly into solid carbon; instead, it first forms an intermediate chemical state before depositing on the electrode. The researchers tested different salt mixtures and electrode materials and found that the fundamental two-step reaction remained consistent across all combinations, but changing the materials altered the physical structure of the deposited carbon—different electrode surfaces and salt chemistries caused the carbon atoms to arrange in different geometric configurations. Control over the physical structure is a key technological advance in this study. Battery-grade graphite requires a very specific crystal orientation; in electric vehicle batteries, the carbon layers must be uniformly spaced so that energy-carrying ions can slide smoothly between them. Since changing the input materials changes the final carbon arrangement, scientists can tune the system accordingly to produce battery-grade graphite.
Mike Whittaker, a Berkeley Lab scientist involved in the project, stated that this represents a significant step in the broader effort to use molten salt for synthesizing critical materials and battery materials. He noted that if the process could be run at lower temperatures using inexpensive salts, it could be implemented in many locations and produce enough graphite to enter the battery supply chain. However, engineering challenges remain before industrial-scale operation can be achieved. The current system requires a continuous energy supply to keep the salt molten at 500°C. The team concluded that the next steps involve identifying the optimal combination of molten salt, electrode materials, temperature, and voltage to produce carbon materials such as graphite, while also scaling up the method's output to industrially viable levels. Scaling from the microscopic reaction cell to a full-scale reactor requires careful management of gas flow, heat distribution, and current density across larger electrode surfaces. If these operational hurdles are overcome, the technology could directly utilize captured industrial emissions to supply synthetic graphite.
