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ORNL team devises electrocatalyst for direct conversion of CO2 into ethanol with high selectivity; pushing the combustion reaction in reverse

Researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL) have developed an electrocatalyst which operates at room temperature and in water for the electroreduction of dissolved CO2 with high selectivity for ethanol. Their finding was serendipitous. An open-access paper on their work appears in the journal ChemistrySelect.

The team used a catalyst made of carbon, copper and nitrogen and applied voltage to trigger a chemical reaction that essentially reverses the combustion process. With the help of the nanotechnology-based catalyst which contains multiple reaction sites, the solution of carbon dioxide dissolved in water turned into ethanol with a yield of 63%. Typically, this type of electrochemical reaction results in a mix of several different products in small amounts.

We discovered somewhat by accident that this material worked. 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.

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. Ethanol was a surprise—it’s extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst.

—Adam Rondinone, lead author

The catalyst’s novelty lies in its nanoscale structure, consisting of copper nanoparticles embedded in carbon spikes. This nano-texturing approach avoids the use of expensive or rare metals such as platinum that limit the economic viability of many catalysts.

Carbon_nanospikes
ORNL researchers developed a catalyst made of copper nanoparticles (seen as spheres) embedded in carbon nanospikes that can convert carbon dioxide into ethanol. Click to enlarge.

The researchers’ initial analysis suggests that the spiky textured surface of the catalysts provides ample reactive sites to facilitate the carbon dioxide-to-ethanol conversion.

Given the technique’s reliance on low-cost materials and an ability to operate at room temperature in water, the researchers believe the approach could be scaled up for industrially relevant applications. For instance, the process could be used to store excess electricity generated from variable power sources such as wind and solar.

A process like this would allow you to consume extra electricity when it’s available to make and store as ethanol. This could help to balance a grid supplied by intermittent renewable sources.

—Adam Rondinone

The researchers plan to refine their approach to improve the overall production rate and further study the catalyst’s properties and behavior.

The work was supported by DOE’s Office of Science and used resources at the ORNL’s Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

Resources

  • Song, Y., Peng, R., Hensley, D. K., Bonnesen, P. V., Liang, L., Wu, Z., Meyer, H. M., Chi, M., Ma, C., Sumpter, B. G. and Rondinone, A. J. (2016) “High-Selectivity Electrochemical Conversion of CO2 to Ethanol using a Copper Nanoparticle/N-Doped Graphene Electrode”, ChemistrySelect doi: 10.1002/slct.201601169

Comments

Davemart

Video here:

https://phys.org/news/2016-10-nano-spike-catalysts-carbon-dioxide-ethanol.html

They have hit up to 70% in purer samples.

SJC

Sequester CO2 from power plants in empty natural gas wells then make the hydrogen using electricity from wind turbines and concentrated heat from the sun. Sell the oxygen for medical and industrial uses to offset the costs. You can make methanol, ethanol, gasoline, kerosene and diesel.

mahonj

@SJC - that's it, sounds like a better deal than making hydrogen because at least ethanol is a liquid and can be blended into gasoline.

Davemart

Hi SJC:

In this system the hydrogen comes from the water the CO2 is dissolved in.

All that would be needed is an electricity supply.

SJC

My method has been proven on a large scale.

Engineer-Poet
My method has been proven on a large scale.

O RLY?  Where?  Tell us what Green country has gone petroleum-free that way.

I find it both amusing and revolting that people suggest collecting CO2 from fossil-fired powerplants to produce other fuels.  This STILL dumps fossil carbon in the atmosphere in planet-killing amounts, YOU IDIOTS!  The only way to make this sort of thing work is to cycle the carbon from some kind of store (e.g. the atmosphere, or CO2 in wells) into storable energy and back again.  You can't mine fossil carbon any faster than weathering removes it.

I'm not sure I'm interpreting Figure 5 in the paper correctly, but it looks like the bulk of the applied energy at 1.2 volts potential is converted to EtOH, CO and H2.  The CO and H2 fractions are suitable for synthesis of MeOH, and the fraction turned to CH4 can be used for short-term storable fuel.  This is amazingly close to the Holy Grail of the Renewablists:  they can turn electricity into storable liquids, and with SOFCs they can turn the liquids back into electricity.  Ultimately, it comes down to "what does it cost?"

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