Carbon dioxide may be history soon. A group of researchers at Oak Ridge National Laboratory (ORNL) have developed a method to get rid of it. Better, they found a way to convert carbon dioxide - a greenhouse gas - into ethanol, which can be used to store energy or to directly produce mechanical work.
Lead by ORNL’s Adam Rondinone, the team of researchers accidentally discovered that a carbon catalyst used to speed a chemical reaction reacted on its own. "We discovered somewhat by accident that this material worked," said Rondinone. “We were trying to study the first step of a proposed reaction when we realized that the catalyst was doing the entire reaction on its own."
When the nanotechnology-based catalyst, made of carbon, copper and nitrogen, was subjected to voltage, the resulting chemical reaction was essentially to reverse the combustion process. The catalyst was being used in a solution of carbon dioxide dissolved in water, but to the researchers’ surprise, the solution was turned into ethanol with a 63% yield at the end of the reaction.
"We're taking carbon dioxide, a waste product of combustion, and we're pushing that combustion reaction backwards with very high selectivity to a useful fuel," Rondinone said. "Ethanol was a surprise -- it's extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst."
The catalyst behavior is due to its nanoscale structure, made of carbon spikes with embedded copper nanoparticles. This synthesis avoids the use of expensive materials such as silver or platinum. "By using common materials, but arranging them with nanotechnology, we figured out how to limit the side reactions and end up with the one thing that we want," Rondinone said.
The success of this reaction, according to the researchers, is due to the spiky-textured surface of the catalysts, thus allowing multiple reactive sites to perfume the reaction. “They are like 50-nanometer lightning rods that concentrate electrochemical reactivity at the tip of the spike," Rondinone said.
The researchers believe this approach could be scaled up industrially for many practical uses. For instance, it could be used to store excess energy from alternative power generators. "A process like this would allow you to consume extra electricity when it's available to make and store as ethanol," Rondinone said. "This could help to balance a grid supplied by intermittent renewable sources."
The results of the research were published in the ChemistrySelect only publication: http://onlinelibrary.wiley.com/doi/10.1002/slct.201601169/abstract;jsessionid=1DC29E793FEA1CB1F9AE01B8277D69AB.f02t01.