The Department of Energy Learned How to Turn Carbon Dioxide Into Liquid Fuel

By Caroline Delbert

Researchers at Argonne National Laboratory say they’ve found a breakthrough way to recycle carbon dioxide into energy-rich ethanol fuel. The secret is an electrified catalyst made from copper and carbon, which the researchers say can be powered using low-cost off-peak or renewable energy. What results is a process that’s more than 90 percent effective, which they say is far higher than any similar existing process.

Northern Illinois University professor and participating Argonne researcher Tao Xu says the new catalyst isn’t just a single stop that can produce ethanol—it’s the first step down a possible long list of ways to turn carbon dioxide into other useful chemicals. Despite the obvious plenitude of carbon dioxide, recycling it effectively into new things has been hard because of how stable and chemically stubborn the molecules are.

Once we have an efficient and plentiful catalyst, the difference is like counting your full piggy bank by hand versus dumping it into a Coinstar machine. Lowering the cost to begin breaking up the carbon dioxide means a variety of new processes could open up and become feasible. The most immediate opportunities are to turn carbon dioxide into other hydrocarbons. If the process is efficient enough, it could even exceed the energy cost of mitigation of carbon dioxide by depositing it in bedrock, for example.

So what is this magic catalyst? It’s a carefully arranged network of copper atoms on a supporting structure made of carbon. The reaction’s efficiency hinges on how well the copper atoms are spread out, in fact. “The FE of ethanol was highly sensitive to the initial dispersion of Cu atoms and decreased significantly when CuO and large Cu clusters become predominant species,” the researchers explain.

Basically, the copper filter begins to cluster up as it undergoes the chemical reaction that produces ethanol, meaning after a certain time it must be realigned and reset. “Operando X-ray absorption spectroscopy identified a reversible transformation from atomically dispersed Cu atoms to Cun clusters on application of electrochemical conditions,” the researchers continue. The energized copper atoms apply low voltage that breaks the carbon dioxide molecules apart. They then rebond, from CO₂ into C₂H₆O.

There are questions here: Does the reaction require absolutely pure carbon dioxide, which is unusual to find in nature? This is an obstacle with most kinds of recycling, from a pizza box or the wrong kind of plastic all the way down to the microscopic level. What’s the hydrogen source? Hydrogen is also costly to separate and, as it stands today, primarily separated using fossil fuels. The catalyst is exciting, but that doesn’t erase existing concerns about how this kind of reaction works.

Ethanol is blended into most American consumer gas products, and its source from waste corn is also an inefficient process. There’s an opportunity to lower the cost (and political subsidy cost) of ethanol used in these blends. All in all, this catalyst is an exciting tool that could have a domino effect on several different kinds of energy research.

This article appeared on the Popular Mechanics website at https://www.popularmechanics.com/science/a33573417/carbon-dioxide-ethanol-catalyst/


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