Like me, most everyone will pop electrical generation in mind when thinking about solar cells. But what if there were other products, would they garner attention? If the production could be stored with technology on hand for a very, very long time would that get some attention? The idea that solar cells would make something ready to store, useful across a wide array of uses such as heating and transport – that might be a goal of massive significance. Let me introduce you to a solar powered methane or other hydrocarbon production system that just recently saw its preliminary patent filing and a paper in The American Chemical Society’s journal Nano Letters from Craig A. Grimes and his team at Pennsylvania State University.

Photocatalytic Converter CO2 & H2O to Hydrocarbons. Click image for more.

Photocatalytic Converter CO2 & H2O to Hydrocarbons. Click image for more.

The Penn State researchers at the Department of Electrical Engineering and Materials Research Institute use dual catalysts to efficiently turn carbon dioxide and water vapor into methane and other hydrocarbons using titania nanotubes in a process using solar for the energy source. Chemically converting water and carbon dioxide to methane seems simple on paper — one carbon dioxide molecule and two water molecules become one methane molecule and two oxygen molecules. But the energy needed for the reaction to occur is at least eight photons for each produced molecule.

In the Nano Letter paper the team notes, “Recycling of carbon dioxide via conversion into a high energy-content fuel, suitable for use in the existing hydrocarbon-based energy infrastructure, is an attractive option, however the process is energy intense and useful only if a renewable energy source can be used for the purpose.”

Grimes says in the Penn State news piece, “Converting carbon dioxide and water to methane using photocatalysis is an appealing idea, but historically, attempts have had very low conversion rates. To get significant hydrocarbon reaction yields require an efficient photocatalyst that uses the maximum energy available in sunlight.”

The dual catalyst describes as titanium dioxide nanotubes doped with nitrogen and coated with a thin layer of both copper and platinum to converts a mixture of carbon dioxide and water vapor to methane. The serious results are using visible outdoor light; they are reporting a 20-times higher yield of methane than previously published attempts conducted in laboratory conditions using intense ultraviolet light exposure.

The team used natural sunlight to test their nanotubes in a chamber containing a mix of water vapor and carbon dioxide. They exposed the co-catalyst sensitized nanotubes to sunlight for 2.5 to 3.5 hours when the sun was producing between 102 and 75 milliwatts for each square centimeter exposed.

The research story is nanotubes annealed at 600 degrees Celsius and coated with copper yielded the highest amounts of hydrocarbons and that the same kind of nanotubes coated with platinum actually yielded more hydrogen, while the copper coated nanotubes produced more carbon monoxide. Both hydrogen and carbon monoxide are normally occuring intermediate steps in the process and as the building blocks of syngas, can be used to make liquid hydrocarbon fuels.

The team then built a nanotube array with about half the surface coated in copper and the other half in platinum, they enhanced the hydrocarbon production and eliminated carbon monoxide. The yield for these dual catalyst nanotubes was 163 parts per million of hydrocarbons an hour for each square centimeter. The yield from titania nanotubes without either copper or platinum catalysts is only about 10 parts per million, or a 16.3 fold increase in productivity using the dual catalyst innovation.

Grimes adds, “If we uniformly coated the surface of the nanotube arrays with copper oxide, I think we could greatly improve the yield.”

This is a ‘first result’ kind of breakthrough. The team learned that lengthening the titanium dioxide tubes, which for other applications increases yield, does not improve results. “We think that distribution of the sputtered (the method of spreading) catalyst nanoparticles is at the top surface of the nanotubes and not inside and that is why increased length does not improve the reaction,” says Grimes.

The most practical news is that the catalysts shifted the reaction from one that used only the energy in ultraviolet light to one that used other wavelengths of visible light and therefore more of the sun’s energy. This is a very significant innovation.

There is a great deal to do in this field with Penn State leading the way now. The research team is now working on converting their batch reactor into a continuous flow-through design that they believe will significantly increase yields.

Methane is already an accelerating fuel market with the U.S. military deploying fuel cells, more marketing and political efforts to convert personal transport to methane or natural gas and the Pickens Plan pressing for substituting methane products for oil imports.

These points all make clear that the Penn State team’s effort is much more significant than most people realize. I’m duly impressed and wish to send along a congratulatory thought to Craig Grimes, Oomman K. Varghese and Maggie Paulose, Materials Research Institute research scientists and Thomas J. LaTempa, graduate student in electrical engineering.


8 Comments so far

  1. A New Way of Production from Solar Energy | New Energy and Fuel on March 9, 2009 7:54 AM

    […]   A New Way of Production from Solar Energy | New Energy and Fuel […]

  2. sonja p on December 16, 2009 12:39 PM

    I believe solar energy and the technology is rapidly growing

  3. Francois P on December 17, 2009 11:56 AM

    Solar energy is exciting and I believe it holds a great future. However it’s not so expensive anymore, but not cheap either.

  4. wolfdaddy74701 on January 22, 2010 8:05 PM

    I just dropped $40k on a 5 kw solar array for our house, and it sounds to me like this could provide enough methane to run a 15 kw generator at my house at least 6 hours a day. Until we start hearing about costs, or actual production expectations, it seems like so much nanotube pie in the sky. Seriously, this is exciting tech., but we need real world, cost-effective solutions that can be used directly by consumers now. Sterling engines and the new solar cells that are virtually unaffected by angle of incidence are cool, but the only people who can get their hands on them are the same energy producers who got us into this mess to begin with. Put clean power in the hands of the people, and we’ll save money on transmission and middle men fees.

  5. Kyle Bailey on October 6, 2010 12:26 AM

    solar energy will get cheaper in the future and more efficient too

  6. Beverage Dispenser  on October 20, 2010 11:46 AM

    solar energy is one of the best options that we can get if we want to go green in power generation.-*

  7. Flatware Sets · on November 9, 2010 1:20 PM

    solar energy should be the stuff that we should harness instead of those fossil fuels “”

  8. marylewis21 on October 18, 2017 4:19 AM

    I believe in solar energy and the technology. I recently updated my website, kindly visit

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