Carbon Nanotubes from the Sky to Mitigate Climate Change: Incentivized Greenhouse Gas Removal By Its Transformation to Valuable Commodities
Authors: Licht Stuart , Johnson Marcus , Lefler Matthew J. , Vicini Juan 
Published: February 2020

As the levels of carbon dioxide increase in the Earth’s atmosphere, this greenhouse gas’s effects on climate change including species extinction, flooding, draught, famine and economic disruption become increasingly apparent. An incentive to remove CO2 is provided by a low energy, low cost, high yield conversion to valuable products such as carbon nanotubes. Displaying superior strength, conductivity, flexibility and durability, carbon nanotube (CNT) applications had been limited due to the cost intensive complexities of their synthesis. An inexpensive source of CNTs made from carbon dioxide will facilitate the rate of its adoption as an important societal resource for the building, aerospace, transportation, renewable energy, sporting and consumer electronics industries, while concurrently consuming carbon dioxide. We present an inexpensive, high-yield and scale-able synthesis of CNTs.
We show a new, unexpected chemistry for the effective capture of CO2 and its transformation at high yield and low energy, by dissolution in a molten carbonate electrolyte, and electrolysis splitting it to carbon nanotubes and oxygen.1-9 The CO2 reactant is directly absorbed from air (without the need for pre-concentration), or can be used and removed from industrial, home or transportation emissions.
It is demonstrated that common metals act as CNT nucleation sites in molten media to efficiently drive the high yield electrolytic conversion of CO2 dissolved in molten carbonates to CNTs. We accomplish this by electrochemically reducing CO2 on steel electrodes in a molten carbonate electrolyte. The CNT structure is tuned by controlling the electrolysis conditions, such as the addition of trace common metals to act as CNF nucleation sites, the composition of the carbonate electrolyte, and the control of temperature and current density. Upward scalability of the process is demonstrated over several orders of magnitude.

1Ren, Li, Lau, Gonzalez-Urbina, Licht, One-pot synthesis of carbon nanofibers from CO2,

Nano Letters

, 15, 6142 (2015).

2Ren, Lau, Lefler, S. Licht, The minimum electrolytic energy needed to convert carbon dioxide by electrolysis in carbonate melts,
J. Phys. Chem., C, 119, 23342 (2015).

3Licht, Douglas, Ren, Carter, Lefler, Pint, Carbon Nanotubes Produced from Ambient Carbon Dioxide for Environmentally Sustainable Lithium-Ion & Sodium-Ion Battery Anodes,
ACS Central Science, 2, 162 (2015).

4Ren, Lau, Lefler, Licht, The minimum electrolytic energy needed to convert carbon dioxide by electrolysis in carbonate melts,
J. Phys. Chem., C, 119, 23342 (2015).

5Lau, Dey, Licht, Thermodynamic assessment of CO2to carbon nanofiber transformation for carbon sequestration in a combined cycle gas or a coal power plant,
Energy Conservation and Management, 122, 400 (2016).

6Wu, Li, Ji, Liu, Li, Yuan, Zhang, Ren, Lefler, Wang, Licht, One-Pot Synthesis of Nanostructured Carbon Material from Carbon Dioxide via Electrolysis in Molten Carbonate Salts,
Carbon, 6, 27760 (2016).

7Ren, Licht, Tracking airborne CO2mitigation and low cost transformation into valuable carbon nanotubes,

Scientific Reports

, 106, 208 (2016).

8Ren, Wang, Johnson, Singhal, Licht, Transformation of the greenhouse gas CO2 by molten electrolysis into a wide controlled selection of carbon nanotubes,
J. CO

2

Utilization
,18, 335 (2017).

9Licht, Co-Production of Cement and Carbon Nanotubes with a Carbon Negative Footprint,
J. CO

2

Utilization
,18, 378 (2017).

Figure: Molten carbonate electrolysis pathways transforming CO2 into a carbon nanotubes.

Figure 1