Researchers at George Washington University led by Prof. Stuart Licht have been working for years on developing and evolving a process for the high-yield, low-energy synthesis of oxygen and graphene nanocarbons (GNCs), such as carbon nanotubes, by the electrolysis of CO₂ in molten carbonate (Li₂CO₃). (E.g., earlier post)

A 11,000 square centimeter area C2CNT electrode (redhot and after cooling) with a several inch thick layer of carbon nanotubes made directly from CO₂ removed from the exhaust gas at the Shepard Natural Gas Power Plant, Calgary, Canada. S. Licht, George Washington University.

In 2017, C2CNT was founded to commercialize the process. Now, C2CNT and Licht have replaced the capital-intensive CO₂ splitting component of the process by a replacement which is much more available, and has far lower demand: strontium carbonate (mainly used today for pyrotechnics).

In an open-access paper in Communications Chemistry the team reports the fundamental thermodynamics and experimental chemistry of why this strontium salt, unlike other salts, is an ideal replacement for the costly lithium carbonate, expediting C2CNT (CO₂ to carbon nanotechnology) decarbonization deployment.

… high Li₂CO₃ cost and its competitive use as the primary raw material for EV batteries are obstacles. Common alternative alkali or alkali earth carbonates are ineffective substitutes due to impure GNC products or high energy limitations. A new decarbonization chemistry utilizing a majority of SrCO₃ is investigated.

SrCO₃ is much more abundant, and an order of magnitude less expensive, than Li₂CO₃. The equivalent affinities of SrCO₃ and Li₂CO₃ for absorbing and releasing CO₂ are demonstrated to be comparable, and are unlike all the other alkali and alkali earth carbonates.

The temperature domain in which the CO₂ transformation to GNCs can be effective is <800 °C. Although the solidus temperature of SrCO₃ is 1494 °C, it is remarkably soluble in Li₂CO₃ at temperatures less than 800 °C, and the electrolysis energy is low. High purity CNTs are synthesized from CO₂ respectively in SrCO₃-based electrolytes containing 30% or less Li₂CO₃.

—Licht et al.

Resources

• Licht, G., Hofstetter, K., Wang, X. et al. A new electrolyte for molten carbonate decarbonization. Commun Chem 7, 211 (2024). doi: 10.1038/s42004-024-01306-z