Posted on 04/11/2012 8:26:05 AM PDT by Red Badger
Copper -- the stuff of pennies and tea kettles -- is also one of the few metals that can turn carbon dioxide into hydrocarbon fuels with relatively little energy. When fashioned into an electrode and stimulated with voltage, copper acts as a strong catalyst, setting off an electrochemical reaction with carbon dioxide that reduces the greenhouse gas to methane or methanol.
Various researchers around the world have studied copper’s potential as an energy-efficient means of recycling carbon dioxide emissions in powerplants: Instead of being released into the atmosphere, carbon dioxide would be circulated through a copper catalyst and turned into methane — which could then power the rest of the plant. Such a self-energizing system could vastly reduce greenhouse gas emissions from coal-fired and natural-gas-powered plants.
But copper is temperamental: easily oxidized, as when an old penny turns green. As a result, the metal is unstable, which can significantly slow its reaction with carbon dioxide and produce unwanted byproducts such as carbon monoxide and formic acid.
Now researchers at MIT have come up with a solution that may further reduce the energy needed for copper to convert carbon dioxide, while also making the metal much more stable. The group has engineered tiny nanoparticles of copper mixed with gold, which is resistant to corrosion and oxidation. The researchers observed that just a touch of gold makes copper much more stable. In experiments, they coated electrodes with the hybrid nanoparticles and found that much less energy was needed for these engineered nanoparticles to react with carbon dioxide, compared to nanoparticles of pure copper.
A paper detailing the results will appear in the journal Chemical Communications; the research was funded by the National Science Foundation. Co-author Kimberly Hamad-Schifferli of MIT says the findings point to a potentially energy-efficient means of reducing carbon dioxide emissions from powerplants.
“You normally have to put a lot of energy into converting carbon dioxide into something useful,” says Hamad-Schifferli, an associate professor of mechanical engineering and biological engineering. “We demonstrated hybrid copper-gold nanoparticles are much more stable, and have the potential to lower the energy you need for the reaction.”
Going small
The team chose to engineer particles at the nanoscale in order to “get more bang for their buck,” Hamad-Schifferli says: The smaller the particles, the larger the surface area available for interaction with carbon dioxide molecules. “You could have more sites for the CO2 to come and stick down and get turned into something else,” she says.
Hamad-Schifferli worked with Yang Shao-Horn, the Gail E. Kendall Associate Professor of Mechanical Engineering at MIT, postdoc Zichuan Xu and Erica Lai ’14. The team settled on gold as a suitable metal to combine with copper mainly because of its known properties. (Researchers have previously combined gold and copper at much larger scales, noting that the combination prevented copper from oxidizing.)
To make the nanoparticles, Hamad-Schifferli and her colleagues mixed salts containing gold into a solution of copper salts. They heated the solution, creating nanoparticles that fused copper with gold. Xu then put the nanoparticles through a series of reactions, turning the solution into a powder that was used to coat a small electrode.
To test the nanoparticles’ reactivity, Xu placed the electrode in a beaker of solution and bubbled carbon dioxide into it. He applied a small voltage to the electrode, and measured the resulting current in the solution. The team reasoned that the resulting current would indicate how efficiently the nanoparticles were reacting with the gas: If CO2 molecules were reacting with sites on the electrode — and then releasing to allow other CO2 molecules to react with the same sites — the current would appear as a certain potential was reached, indicating regular “turnover.” If the molecules monopolized sites on the electrode, the reaction would slow down, delaying the appearance of the current at the same potential.
The team ultimately found that the potential applied to reach a steady current was much smaller for hybrid copper-gold nanoparticles than for pure copper and gold — an indication that the amount of energy required to run the reaction was much lower than that required when using nanoparticles made of pure copper.
Going forward, Hamad-Schifferli says she hopes to look more closely at the structure of the gold-copper nanoparticles to find an optimal configuration for converting carbon dioxide. So far, the team has demonstrated the effectiveness of nanoparticles composed of one-third gold and two-thirds copper, as well as two-thirds gold and one-third copper.
Hamad-Schifferli acknowledges that coating industrial-scale electrodes partly with gold can get expensive. However, she says, the energy savings and the reuse potential for such electrodes may balance the initial costs.
“It’s a tradeoff,” Hamad-Schifferli says. “Gold is obviously more expensive than copper. But if it helps you get a product that’s more attractive like methane instead of carbon dioxide, and at a lower energy consumption, then it may be worth it. If you could reuse it over and over again, and the durability is higher because of the gold, that’s a check in the plus column.”
This story is republished courtesy of MIT News (http://web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.
Quick ~ somebody work this out ~ Coal + Air =, then we take the CO2 and convert that to Methane ~ then we burn that again. Remember to account for the additional O from the atmosphere.
There will be other byproducts that can be handled as solids.
The cost of the catalysts is probably far less than the costs of the lawyers!
Let’s see CO2 has one carbon atom and two oxygen atoms. Methane is CH4, that is one carbon atom and 4 hydrogen atoms. I never see in the article where the hydrogen atoms are going to come from. Besides as cheap as methane is today I don’t see the point.
I think you guys are missing something. It sounds to me like the whole article is talking about a breakthrough in combining CO2 and hydrogen, into methane. Thus its not a perpetual motion machine. The hydrogen will be supplied outside of this process. That is the only thing that make sense to me.
Very interesting!
I wonder whether this science would work with other non-oxidizing metals like platinum or paladium and copper, as our catalytic converters already use these metals to reduce noxious gasses.
Perhaps the resulting methene could be recycled into the combustion process thru introducing it back into a turbocharger
Now if we can figure how to reverse the process we can turn coal into copper and gold.
“The hydrogen will be supplied outside of this process”
Of course hydrogen can be supplied at a cheap price. /s
Actually, this is really promising. It’s true that you need to add energy to convert the CO2 to hydrocarbons, but solar cells are certainly capable of providing the current necessary to facilitate the conversion. If this technology proves feasible, it would be a great step toward energy independence.
BTW, the oxygen to burn the hydrocarbons is simply recycled back to the atmosphere when the CO2 is converted to CH4.
This process also suggests a path to create natural gas inorganically in the earth’s crust: carbonate rocks, heat, and a little hydrogen could do the trick. The difficult part is creating the hydrogen efficiently.
Talk to Al Gore. He has been very successful turning coal into gold. I don't think he bothers with the coppers.
So we steam reform methane to make the hydrogen, to combine with CO2 with yet more energy consumption, to make methane?
This is feeding off the global warming scam of carbon capture, it is a net loss energy system.
The chemical reaction for combustion of methane is:
CH4 + 2 O2 → CO2 + 2 H2O (ΔH = −891 kJ/mol (at standard conditions))
Any reaction converting CO2 back into methane will consume 891 kJ/mol if 100% efficient. And no process is 100% efficient. So (and thermodynamics guarantees this result, hence no 'perpetual motion' machines) converting the same chemical reaction back and forth must ALWAYS result in a net energy LOSS. I'm a physicist, not a chemist, but this is pretty basic stuff.
The reaction took place in water. So I assume the water was the source of the hydrogen.
Maybe this could make coal-to-liquid more efficient? My understanding of the process is that it takes energy (in the form of heat) and CO2. Maybe this method could do the job using less energy?
Ultimately I think the goal of this research was to make it cheaper to reduce CO2 emissions, however it may be useful in other applications.
Thermodynamics should be required education for every citizen. Especially the morons in congress.
The process involves immesing the electrode in water through which CO2 is passed, so the current will break down the water molecules to obtain the hydrogen. The reaction produces 3 molecules of oxygen for each molecule of methane: 2H2O + CO2 = CH4 + 3O2
Then you need to add the energy required to separate the molecular bonds of water.
As an old engineer myself (ChemE), I must agree.
But this is a new age! The laws of thermodynamics, like the Constitution, are full of negative restrictions. We can just hopey-changey them to something else. ;D
The NappyOne
My bad- the reaction is produces 2 oxygen molecules for each methane molecule:
4xH2O + 2xCO2 = 2xCH4 + 4xO2
There is no “free” energy, however if the technology is more efficient than existing processes to create synthetic hydrocarbons it could be useful.
“hydrocarbon fuels with relatively little energy”
Relative to what is the $64 question.
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