Sustainable ethanol from carbon dioxide? A possible path

Stanford scientists have designed a copper catalyst that produces ethanol from carbon dioxide and water.

Most cars and trucks in the United States run on a blend of 90 percent gasoline and 10 percent ethanol, a renewable fuel made primarily from fermented corn. But to produce the 14 billion gallons of ethanol consumed annually by American drivers requires millions of acres of farmland.

A recent discovery by Stanford University scientists could lead to a new, more sustainable way to make ethanol without corn or other crops. This promising technology has three basic components: water, carbon dioxide and electricity delivered through a copper catalyst. The results are published in the Proceedings of the National Academy of Sciences (PNAS).

“One of our long-range goals is to produce renewable ethanol in a way that doesn’t impact the global food supply,” said study principal investigator Thomas Jaramillo, an associate professor of chemical engineering at Stanford and of photon science at the SLAC National Accelerator Laboratory.

Scientists would like to design copper catalysts that selectively convert carbon dioxide into higher-value chemicals and fuels, like ethanol and propanol, with few or no byproducts. But first they need a clear understanding of how these catalysts actually work. That’s where the recent findings come in.

Copper crystals

For the PNAS study, the Stanford team chose three samples of crystalline copper, known as copper (100), copper (111) and copper (751). Scientists use these numbers to describe the surface geometries of single crystals.

“Copper (100), (111) and (751) look virtually identical but have major differences in the way their atoms are arranged on the surface,” said Christopher Hahn, an associate staff scientist at SLAC and co-lead lead author of the study. “The essence of our work is to understand how these different facets of copper affect electrocatalytic performance.”

In previous studies, scientists had created single-crystal copper electrodes just 1-square millimeter in size.

“With such a small crystal, it’s hard to identify and quantify the molecules that are produced on the surface,” Hahn explained. “This leads to difficulties in understanding the chemical reactions, so our goal was to make larger copper electrodes with the surface quality of a single crystal.”

To create bigger samples, Hahn and his co-workers at SLAC developed a novel way to grow single crystal-like copper on top of large wafers of silicon and sapphire.

“What Chris did was amazing,” Jaramillo said. “He made films of copper (100), (111) and (751) with 6-square centimeter surfaces. That’s 600 times bigger than typical single crystals.

Catalytic performance

To compare electrocatalytic performance, the researchers placed the three large electrodes in water, exposed them to carbon dioxide gas and applied a potential to generate an electric current.

The results were clear. When a specific voltage was applied, the electrodes made of copper (751) were far more selective to liquid products, such as ethanol and propanol, than those made of copper (100) or (111). The explanation may lie in the different ways that copper atoms are aligned on the three surfaces.

“In copper (100) and (111), the surface atoms are packed close together, like a square grid and a honeycomb, respectively” Hahn said. “As a result, each atom is bonded to many other atoms around it, and that tends to make the surface more inert.”

But in copper (751), the surface atoms are further apart.

“An atom of copper (751) only has two nearest neighbors,” Hahn said. “But an atom that isn’t bonded to other atoms is quite unhappy, and that makes it want to bind stronger to incoming reactants like carbon dioxide. We believe this is one of the key factors that lead to better selectivity to higher-value products, like ethanol and propanol.”

Ultimately, the Stanford team would like to develop a technology capable of selectively producing carbon-neutral fuels and chemicals at an industrial scale.

“The eye on the prize is to create better catalysts that have game-changing potential by taking carbon dioxide as a feedstock and converting it into much more valuable products using renewable electricity or sunlight directly,” Jaramillo said. “We plan to use this method on nickel and other metals to further understand the chemistry at the surface. We think this study is an important piece of the puzzle and will open up whole new avenues of research for the community.”

Read more at ScienceDaily

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Comments (8)

  • Avatar

    JayPee

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    It always has been theoretically possible to produce ethanol from carbonated water.
    George Gamow said so in the 50’s.
    Professor Gamow considered that it was to be regarded as proof that
    carbonated water is a living substance.
    And now, they may have found a proper catalyst.

    Reply

  • Avatar

    Sonnyhill

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    Beer is proof that God loves us and wants us to be happy – Ben Franklin.
    People who survived the Black Plague drank beer instead of water.
    Beer made Budweiser.
    Carbonation,ethanol,life. If only it was that easy.

    Reply

  • Avatar

    David Lewis

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    It is time to get Alice out of Wonderland.

    The energy to make the electricity has to come from some where. With the high cost of solar and wind power, the limited hydro electric resources, and the unpopularity of nuclear, the electricity for this process would have to come from fossil fuels. It makes more sense to convert the fossil fuel into something engines can run off of.

    This article over looks a main reason for using ethanol from corn for fuel. The farmers strongly lobby for it so they will have the extra income. I have relatives in Nebraska that are all for it.

    Reply

  • Avatar

    Sonnyhill

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    President Trump will be making a speech in Iowa today.

    Reply

  • Avatar

    Spurwing Plover

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    I have seen pictures of the estates of envromental minded celeberties and none of them had any solar pannels on their fancy digs and many like Al Gore and John Travolta(Who has a 707)with their private jets and DiCaprio who rented a arab oil tycoons yacht and who flew from Paris to New York and back to Paris to ecsept some dumb envomental award

    Reply

  • Avatar

    G

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    I’m all for any new and efficient means to produce ethanol as a fuel.

    I’m not in favor of politicians or bureaucrats forcing me to burn it in engines not designed for alcohol. Let the markets decide how such a technology develops. If it is valid and economical you can build it and they will come.

    Reply

  • Avatar

    MCPR

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    Even (or especially) if engineers get this working perfectly, it is sure to cause cancer or birth defects in California. No way the “Green” people are going to let better technology get in the way of their stone-age utopia.

    Reply

    • Avatar

      G

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      LOL! So true!

      Not long ago, America’s leftists proclaimed that we need energy independence to free ourselves from foreign influenced powers and oil wars. Of course, they never thought that was possible, or they wouldn’t have said it… Now that America truly has energy independence via vast new discoveries and clean-burn technologies, they are all out to sabotage and stop that blessing in its tracks. How dare America succeed on its own terms!

      Reply

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