CNTs from CO2 and Electricity

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carbon nanotubes, climate change, CO2 reduction, electrochemistry, solar

Prof. Stuart Licht’s group at George Washington University recently published an article in NanoLetters on the use of high temperature electrolysis to convert CO2 into carbon nanotubes (CNTs) (and other morphologies) and O2:

The process takes place at around 800 C in a molten carbonate salt, which can easily absorb CO2 from air or a flue stream as the carbonate is converted to carbon at the cathode in the electrochemical reactor.  The process could be run as a STEP process (solar thermal electrochemical process), using the sun to heat the electrolysis solution and provide electricity for the electrochemical reaction.

In addition to providing an useful means of sequestering excess CO2 in the atmosphere in the form of solid carbon, there could be great economic incentive for such a process. This article is cited as saying that CNT’s sell for about $25,000 per ton.

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The Methanol Economy

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CO2 reduction, energy, energy storage, hydrogen, methanol, methanol economy

We often hear about and talk about the “Hydrogen Economy“, an energy system that is centered around the use of hydrogen (H2) as the main energy carrier.  Such a system is attractive for three main reasons: i.) the associated CO2 emissions can approach zero (assume H2 is produced from water splitting using renewable electricity from solar or wind), ii.) H2 can be efficiently converted to electricity by H2 fuel cells, and iii.) H2 fuel can be used in many different applications ranging from transportation to general electricity use.

Another alternative is the “Methanol Economy” in which the primary energy carrier is methanol.  The primary advantage of methanol over hydrogen is its ability to be stored as a liquid at room temperature and pressure, making a methanol storage and transport infrastructure much more simple (low cost) and energy efficient.  Currently, methanol is produced predominantly from syngas (CO + H2) produced from fossil fuels, but it can also be made directly from the reduction of CO2 (with H2O providing the H2).

For a high-level overview of the methanol economy, here is an excellent article in Angewandte Chemie written by George Olah, the 1994 Nobel Prize winner in chemistry and major advocate of the methanol economy:

http://onlinelibrary.wiley.com/doi/10.1002/anie.200462121/abstract