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.
Copper — the stuff of pennies...
Actually, that would be Zinc.
Just goes to show you that researchers and writers know little about money.
Silly comment.
Of course you wouldn’t use methane to produce hydrogen to be used to produce methane. One of the holy grails of catalytic chemistry has been efficient water splitting. That is the best place to find hydrogen for this process. And yes, it requires energy. My point was, simply, that if solar energy could create the current necessary to power this reaction, it would be an efficient way to produce a mobile fuel.
Of course, by trapping more solar energy, we could change the earth’s heat balance and create global warming.
(BTW, I am not a warmist, but I believe it is prudent to explore as many alternate energy processes as we can. It’s just good science.)
“Creativity is putting known facts together in new and unusual ways.”
You’re still ahead of me - everything I know about hydrocarbons I learned from watching McGyver. :-)
As for the Hydrogen, you would likely get it from water, but you need energy to separate it. You could get it from H2S, which is interesting because its a byproduct of hydrocarbon refining.
Either way, you have to add energy here to get the hydrogen. Question is whether you could generate enough using solar to make it work at scale.
The earth is producing all kinds of DC power everyday, just by having its metal core turning within the magnetosphere - 186,000 lightening strikes a day.
I saw a video of a refueling tanker manifesting ‘St. Elmo’s Fire’ and the fuel nozzle arc’ing and sparking against the jet its trying to refuel.
Consider they are likely using JP-4, which is pretty flammable and not JP-5, which you could use to put out a cigarette.
Lot’s of free electrical energy out there. It’s just a matter of putting lightning in a bottle, as it were.
But electrolysis of water is far more expensive than steam reforming methane. That makes a bad idea even worse.
This scam is not about energy production, it is about carbon nature. They may have improved the losses but it still operates at a loss.
Apart from recovering and recycling waste CO2, another angle to this process (if it is efficient enough) is that it could be another effective way to store and transport electric power. As methane, it transports nicely.
Isn’t thermodynamics the science that determines the size of showerheads and water reservoirs for toilets as developed by congresscritters?
Hmmm. I believe I’ve used copper to make ethanol too! :)
Will it end up as inefficient as the other "green" technologies?
Well, let's see...First you burn coal to make steam to turn a turbine that drives a generator that produces electricity. The process also produces CO2 which can be reacted with a copper/gold electrode in an undefined solution to produce methane (natural gas). So lets just burn the methane along with the coal, oh oh, we just produced more CO2...Back to the magic cells to make more methane.
At some point could we drop the coal altogether and just burn methane to produce electricity and CO2 while reacting the CO2 with the copper/gold electrodes and the secret sauce (with just a pinch of the electricity produced, leaving enough power to keep our customers smiling!) Let's look a little closer, we have a closed process with a fixed amount of CO2 which we convert to methane using a catalyst and electricity. We then burn the methane, extracting heat to produce electricity and more CO2 to continue the process indefinitely.
Neat! Except that the laws of physics regarding the conservation of energy require that the amount of energy needed to synthesize the methane will be greater than what you can recover by burning the same amount of as fuel. This is why all thermodynamic processes reject heat to the environment (cooling towers!!).
Lastly, converting all the CO2 produced by a coal fired power plant to methane or methanol does not destroy the gas forever, it hides it as unburnt hydrocarbons in the newly produced fuels. As soon as those fuels are burnt, presto, the same amount of CO2 is released into the environment, the energy recovered will be less then the energy input to the synthesis as electricity. And what a long strange trip it's been...
The closed box that produces perpetual energy output is just as imposable as the proverbial "free lunch".
Regards,
GtG
Sounds like enough energy to keep the stack blowing eh!
I have no doubt they will be utterly mystified!
...and I bet the Feds didn’t like it!........
Roger that. I was also thinking of long distance transportation. One of the difficulties of electrical generation is that it needs to be fairly close to the consumer. Long distance transmission is terribly inefficient, and means losing non-trivial amounts of power the farther it goes. This sounds like it might be a good way of storing up energy in one place and moving it over long distances.
CNG meet pipeline. Solar electric + water + CO2 ->CNG.
We run HV transmission lines for hundreds of miles for cost effective generation to consumer.
Long distance transmission is terribly inefficient
A few percentage points of loss is terribly inefficient?
I thought the loss on long distance high voltage lines was more on the order of 10 or 20%. Is that wrong?
The electrical loss of electricity leaving the power plant, through the step-up transformers, across the high voltage transmission line, through the local substation including step-down transformer, across local distribution lines, through the end transformer to the customer meter totals 6~7% typically. The transmission line alone is a fraction of that total.
High Voltage DC lines have even less losses, but the stations of HVAC-HVDC are very expensive and this set up is normally only used to move power either through long distances without intermediate drop off, or systems isolated by frequency.
High Voltage transmission lines are used because as the voltage increases, for the same amount of power flow, current decreases. Losses are impedance (resistance plus reactance) times the current squared. If you double the voltage, halving the current, the losses are quartered. This why we use voltage up to 765kV in the US for long distances.
Thanks skinkinthegrass.
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