Scientists Turn Carbon Monoxide Into Ethanol: Could CO2 Be The Next Clean Energy Source?
Ethanol is cleaner than gasoline and comes from a renewable resource, usually corn. But that doesn't mean it's efficient: it takes millions of acres of land, tons of fertilizer and trillions of gallons of water to make the stuff.
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Now scientists say they may have found a better way. In a study published Wednesday in Nature, chemists at Stanford University explain how they produced ethanol with just a bit of water, cheap copper wire, and some carbon monoxide.
It all started when this group of scientists, led by Matthew Kanan and Christina Li, wanted to know whether there was a way to produce mass quantities of ethanol without the big agricultural and distillation process. Better yet, they wanted to create it from carbon dioxide, the harmful and abundant greenhouse gas, by sucking it out of the air and then subjecting it to chemical reactions. Like modern-day alchemists, they hoped to make clean energy from the refuse of dirty energy.
Just one problem. While they knew how to make carbon monoxide from carbon dioxide, no one had ever developed a good way to make liquid ethanol from carbon monoxide gas. "Most materials are incapable of reducing carbon monoxide," said Kanan, co-author of the new study, in a statement. "Copper is the only exception, but conventional copper is very inefficient." What they needed was a catalyst that would react with the carbon monoxide in a way that could be scaleable in a meet-U.S.-energy-demand kind of way.
So they began toying with modified copper electrodes. "Conventional copper electrodes consist of individual nanoparticles that just sit on top of each other," Kanan explains. Two years prior, he and his group had fabricated a different kind of electrode, which they call oxide-derived copper. These are "made of copper nanocrystals that are all linked together in a continuous network with well-defined grain boundaries," he said.
To test their nanocrystalline copper, they put water (H20) saturated with carbon monoxide gas (CO) into a special container. Then they stuck two electrodes — one positive, one negative — into the water. When water travels through the electrodes and through the water, most kinds of metal electrodes react solely with the water, scattering the elements into two camps: oxygen toward the anode, hydrogen to the cathode. Copper, however, causes ethanol (C2H6O) to form instead of hydrogen. The trick would be if oxide-derived copper used more electricity to make more ethanol.
And, of course, it did. Their results showed that oxide-derived copper was 10 times more efficient than conventional copper at producing ethanol. "The missing piece was the efficient conversion of carbon monoxide to a useful fuel that's liquid, easy to store and nontoxic," Kanan said. "Prior to our study, there was a sense that no catalyst could efficiently reduce carbon monoxide to a liquid. We have a solution to this problem that's made of copper, which is cheap and abundant." He says he hopes that others take this feasibility study and run with it.
In the future, he says, it's possible that companies will be able to draw carbon dioxide out of the air, convert that to carbon monoxide and then use their copper method or something like it to create ethanol. "Technology already exists" to complete the first two parts of that process, Kanan says. His dream is likely a long way off, however. In 2011, the United States alone produced more than 13.5 billion gallons of ethanol, according to The Earth Institute at Columbia University — and 95 percent of that came from corn.
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