Imagine creating essential battery materials by extracting carbon dioxide directly from the atmosphere. This idea, which seems almost magical, has now become a reality thanks to chemists.
The process, known as molten salt electrolysis, employs electrodes on intensely heated salts. This method effectively removes carbon dioxide from the air, rearranges the carbon and oxygen atoms, and solidifies the carbon into materials like graphite.
Scientists have long been curious about the molecular changes occurring during this 500-degree Celsius (932-degree Fahrenheit) reaction. For the first time, they have observed it firsthand.
A team led by chemical physicist Sander Ratso from the University of California, Berkeley, published a paper in Nature Communications. They describe a method that allows real-time monitoring of material transformations and detection of molecular bond vibrations.
“It’s like we added a window to what was previously a closed oven,” Ratso explained to ScienceAlert. “Understanding this reaction and the evolution of carbon structures is crucial for controlling and eventually designing the outcomes of electrolysis.”
Mike Whittaker, an Earth geoscientist at Lawrence Berkeley National Laboratory, sees this as a significant step in producing vital materials for batteries using molten salts. The study offers unprecedented insights into carbon evolution and intermediate species during CO2 electrolysis, identifying a two-step reaction pathway.
Using Raman spectroscopy, researchers observed bands of light that indicated the presence of carbon-adsorbed peroxide as carbon gradually accumulated. This supports a hypothesis from 1999 suggesting peroxide as an intermediate in the process.
“The peroxide band consistently appears and increases alongside carbon deposition, proving that peroxide is the key intermediate in the CO2-to-carbon transformation,” Ratso and his team wrote in their paper.
The type of carbon formed varied with different cathodes, though the core reaction remained unchanged.
On a nickel cathode, carbon appeared as nanotubes and platelet-like structures. Inconel 600 alloy predominantly produced platelets, while gold electrodes resulted in amorphous clumps. Tungsten electrodes yielded amorphous carbon and ‘carbon nano-onions’.
These findings could enable scientists to customize the process based on the desired carbon form, such as those used in batteries, smartphones, and industrial equipment.
Whittaker suggests that with low-cost salts and lower temperatures, this method could be widely adopted, potentially generating enough graphite to support battery supply chains.
Several companies are already utilizing this technology industrially, producing significant quantities of carbon products. Ratso, a co-founder of one such company, notes that current synthesis often relies on trial-and-error methods, which are costly and time-consuming.
The insights gained from operando Raman spectroscopy could streamline and enhance the efficiency of this process.
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Traditional methods of producing carbons for batteries and fuel cells result in high CO2 emissions. Utilizing atmospheric carbon dioxide to source graphite presents an attractive alternative, reducing future emissions while also removing existing ones.
Although carbon capture, utilization, and storage alone won’t resolve climate issues, Ratso is confident that this graphite production technique can contribute significantly.
“The molten salt electrolysis method can produce materials with negative CO2 equivalents when powered by renewable or nuclear energy,” Ratso stated. “I believe this technology could significantly impact environmental CO2 levels.”
The research findings are detailed in Nature Communications.
This article was fact-checked by Michael Irving and edited by Michael Irving. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
