Researchers from C2CNT LLC, Carbon Corp, and George Washington University have developed a new method to separate molten electrolyte from graphene nanocarbon products during the process of capturing carbon dioxide. This breakthrough represents a significant advancement in carbon capture and utilization (CCU), offering a sustainable way to reduce carbon dioxide levels in the atmosphere while producing valuable materials.

The research, led by Professor Stuart Licht, focuses on improving how carbon nanotubes (CNTs) are separated from a material called “carbanogel,” which forms during the electrolysis of carbon dioxide in molten carbonates. Carbanogel is a mix of graphene nanocarbons and molten electrolyte. To extract pure CNTs and reuse the electrolyte, the two must be efficiently separated.

The process begins with the breakdown of carbon dioxide, where the carbon is turned into various forms of graphene nanocarbon, including CNTs, at the cathode (a part of the electrolysis setup). The challenge is to separate the molten electrolyte, which is tightly mixed with the nanocarbons. The researchers achieved high efficiency in separating the electrolyte by using a high-temperature, high-pressure filtration method. They fine-tuned the process by adjusting key factors like the time the material is pressed, the pressure applied, and the type of filter used.

Professor Licht explained, “The carbon dioxide is split into carbon and oxygen with a graphene nanocarbon-electrolyte matrix growing at the electrolysis cathode. This nanocarbon/carbonate electrolyte mix has been termed a carbanogel and is refined through the separation of the electrolyte.” He further emphasized the importance of this separation process, noting that “the electrolyte extraction efficiency in this study is nearly complete, allowing for the substantial recovery of the electrolyte from the graphene nanocarbon product.”

For example, increasing the press time and applying more pressure significantly improved the efficiency of separating the electrolyte. The use of a specific type of filter, known as a Dutch-weave screen, further enhanced the separation, ensuring minimal loss of electrolyte and maximizing the purity of the CNTs.

The impact of this research is significant. By efficiently separating the electrolyte, the process becomes more sustainable and cost-effective, as the reused electrolyte reduces material costs. Additionally, the ability to produce high-quality CNTs directly from carbon dioxide makes this technology a promising solution for both reducing carbon emissions and creating valuable products.

The study also shows that this process can be scaled up, meaning it can be applied to larger quantities of carbanogel, with equipment capable of handling significant amounts. This scalability is crucial for industrial applications, where large volumes of carbon dioxide need to be captured and converted to make a meaningful impact on climate change.

Professor Licht highlighted the potential for further improvements, stating, “Even higher extraction efficiencies can be attained with further refinements such as the application of a vacuum in conjunction with the applied pressure.” As the researchers continue to improve this technology, future studies are expected to explore additional enhancements, such as using vacuum filtration to further increase the efficiency of electrolyte separation. This progress could lead to the widespread adoption of carbon dioxide electrolysis as a practical method for both combating climate change and producing advanced materials.

Journal Reference

Gad Licht, Kyle Hofstetter, Stuart Licht. “Separation of molten electrolyte from the graphene nanocarbon product subsequent to electrolytic carbon dioxide capture.” DeCarbon, 2024. DOI: https://doi.org/10.1016/j.decarb.2024.100044