Breakthrough solar cell captures carbon dioxide and sunlight, produces burnable fuel

July 28, 2016
Simulated sunlight powers a solar cell that converts atmospheric carbon dioxide directly into syngas. Credit: University of Illinois at Chicago/Jenny Fontaine

Researchers at the University of Illinois at Chicago have engineered a potentially game-changing solar cell that cheaply and efficiently converts atmospheric carbon dioxide directly into usable hydrocarbon fuel, using only sunlight for energy.

The finding is reported in the July 29 issue of Science and was funded by the National Science Foundation and the U.S. Department of Energy. A provisional patent application has been filed.

Unlike conventional , which convert sunlight into electricity that must be stored in heavy batteries, the new device essentially does the work of plants, converting into fuel, solving two crucial problems at once. A solar farm of such "artificial leaves" could remove significant amounts of carbon from the atmosphere and produce energy-dense fuel efficiently.

"The new solar cell is not photovoltaic—it's photosynthetic," says Amin Salehi-Khojin, assistant professor of mechanical and industrial engineering at UIC and senior author on the study.

"Instead of producing energy in an unsustainable one-way route from to greenhouse gas, we can now reverse the process and recycle atmospheric carbon into fuel using sunlight," he said.

While plants produce fuel in the form of sugar, the artificial leaf delivers syngas, or synthesis gas, a mixture of hydrogen gas and carbon monoxide. Syngas can be burned directly, or converted into diesel or other hydrocarbon fuels.

The ability to turn CO2 into fuel at a cost comparable to a gallon of gasoline would render fossil fuels obsolete.

Chemical reactions that convert CO2 into burnable forms of carbon are called reduction reactions, the opposite of oxidation or combustion. Engineers have been exploring different catalysts to drive CO2 reduction, but so far such reactions have been inefficient and rely on expensive precious metals such as silver, Salehi-Khojin said.

"What we needed was a new family of chemicals with extraordinary properties," he said.

Salehi-Khojin and his coworkers focused on a family of nano-structured compounds called transition metal dichalcogenides—or TMDCs—as catalysts, pairing them with an unconventional ionic liquid as the electrolyte inside a two-compartment, three-electrode electrochemical cell.

The best of several catalysts they studied turned out to be nanoflake tungsten diselenide.

Amin Salehi-Khojin, UIC assistant professor of mechanical and industrial engineering (left), and postdoctoral researcher Mohammad Asadi with their breakthrough solar cell that converts atmospheric carbon dioxide directly into syngas. Credit: University of Illinois at Chicago/Jenny Fontaine

"The new catalyst is more active; more able to break carbon dioxide's chemical bonds," said UIC postdoctoral researcher Mohammad Asadi, first author on the Science paper.

In fact, he said, the new catalyst is 1,000 times faster than noble-metal catalysts—and about 20 times cheaper.

Other researchers have used TMDC catalysts to produce hydrogen by other means, but not by reduction of CO2. The catalyst couldn't survive the reaction.

"The active sites of the catalyst get poisoned and oxidized," Salehi-Khojin said. The breakthrough, he said, was to use an ionic fluid called ethyl-methyl-imidazolium tetrafluoroborate, mixed 50-50 with water.

"The combination of water and the ionic liquid makes a co-catalyst that preserves the catalyst's active sites under the harsh reduction reaction conditions," Salehi-Khojin said.

The UIC artificial leaf consists of two silicon triple-junction photovoltaic cells of 18 square centimeters to harvest light; the tungsten diselenide and ionic liquid co-catalyst system on the cathode side; and cobalt oxide in potassium phosphate electrolyte on the anode side.

When light of 100 watts per square meter - about the average intensity reaching the Earth's surface - energizes the cell, hydrogen and gas bubble up from the cathode, while free oxygen and hydrogen ions are produced at the anode.

"The diffuse through a membrane to the cathode side, to participate in the carbon dioxide reduction reaction," said Asadi.

The technology should be adaptable not only to large-scale use, like solar farms, but also to small-scale applications, Salehi-Khojin said. In the future, he said, it may prove useful on Mars, whose atmosphere is mostly , if the planet is also found to have water.

"This work has benefitted from the significant history of NSF support for basic research that feeds directly into valuable technologies and engineering achievements," said NSF program director Robert McCabe.

"The results nicely meld experimental and computational studies to obtain new insight into the unique electronic properties of transition metal dichalcogenides," McCabe said. "The research team has combined this mechanistic insight with some clever electrochemical engineering to make significant progress in one of the grand-challenge areas of catalysis as related to energy conversion and the environment."

Explore further: New catalyst converts carbon dioxide to fuel

More information: Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid, Science, science.sciencemag.org/cgi/doi/10.1126/science.aaf4767

Related Stories

New catalyst converts carbon dioxide to fuel

July 30, 2014

Scientists from the University of Illinois at Chicago have synthesized a catalyst that improves their system for converting waste carbon dioxide into syngas, a precursor of gasoline and other energy-rich products, bringing ...

Process holds promise for production of synthetic gasoline

December 2, 2013

A chemical system developed by researchers at the University of Illinois at Chicago can efficiently perform the first step in the process of creating syngas, gasoline and other energy-rich products out of carbon dioxide.

Making green fuels, no fossils required

November 2, 2015

Using solar or wind power to produce carbon-based fuels, which are commonly called fossil fuels, might seem like a self-defeating approach to making a greener world. But when the starting material is carbon dioxide, which ...

Recommended for you

Molecular 'treasure maps' to help discover new materials

March 22, 2017

Scientists at the University of Southampton working with colleagues at the University of Liverpool have developed a new method which has the potential to revolutionise the way we search for, design and produce new materials.

Rare-earths become water-repellent only as they age

March 22, 2017

Surfaces that have been coated with rare earth oxides develop water-repelling properties only after contact with air. Even at room temperature, chemical reactions begin with hydrocarbons in the air. In the journal Scientific ...

Making twisted semiconductors for 3-D projection

March 22, 2017

A smartphone display that can produce 3-D images will need to be able to twist the light it emits. Now, researchers at the University of Michigan and the Ben-Gurion University of the Negev have discovered a way to mass-produce ...

53 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

antialias_physorg
3.9 / 5 (16) Jul 28, 2016
it may prove useful on Mars

Not sure about that. While you can probably get some fuel out of the (very thin) CO2 atmosphere you have to have oxygen to burn that fuel again.

As the famous last words of some unsung SciFi roleplayer go:
"We take our flamers, go down to the planet and torch the alien queen!....Whaddaya mean 'no oxygen in the atmosphere'?"
gregd
1.7 / 5 (15) Jul 28, 2016
Any bets that this technology never sees the light of day again?
epoxy
Jul 28, 2016
This comment has been removed by a moderator.
pntaylor
not rated yet Jul 28, 2016
"hydrogen and *carbon monoxide gas bubble up from the cathode*, while free oxygen and hydrogen ions are produced at the anode.
"The hydrogen ions diffuse through a membrane to the cathode side, to participate in the carbon dioxide reduction reaction," "

So what happens to the carbon monoxide???
greenonions
4.3 / 5 (6) Jul 28, 2016
pntayler
the artificial leaf delivers syngas, or synthesis gas, a mixture of hydrogen gas and carbon monoxide.
There is mountains of info on line about the potential benefits of syngas - http://www.syngas...ngaschem
Eikka
5 / 5 (9) Jul 28, 2016
you have to have oxygen to burn that fuel again.


Tell me, what becomes of CO2 when you remove the carbon?
Whydening Gyre
4.5 / 5 (8) Jul 28, 2016
Yahoo, UIC !!
(My bio-chemist daughter is an alum.:-))
moops
3.7 / 5 (3) Jul 28, 2016
you have to have oxygen to burn that fuel again.


Tell me, what becomes of CO2 when you remove the carbon?


precisely. This process produces both fuel and oxygen. Both must be stored but that is essentially the narrative. we just happen to live on a planet with lots of excess O2 in the atmosphere so we don't need to carry that part.

but, a battery looks much more practical for Mars. If I have to store and carry my oxygen and fuel then the benefits of energy-dense hydrocarbon is pretty much nullified.
marcomatto
5 / 5 (3) Jul 28, 2016
"uses sunlight to remove CO2 from the atmosphere and produce burnable fuel"
Isn't that what trees do?
Eikka
5 / 5 (4) Jul 28, 2016
If I have to store and carry my oxygen and fuel then the benefits of energy-dense hydrocarbon is pretty much nullified.


It's the same thing for batteries as well. It's just not oxygen that does the "oxidizing" but another chemical, and that other chemical is often much heavier than plain old oxygen.

retrosurf
5 / 5 (3) Jul 28, 2016
So what happens to the carbon monoxide???


That's part of the fuel they're talking about. You feed the hydrogen and carbon monoxide into the Fischer-Tropsch process, and you get higher molecular weight carbon-based fuels out of it.
Eikka
5 / 5 (2) Jul 28, 2016
a battery looks much more practical for Mars


And on another point, if you're going to manufacture it from local materials, it's easier to pull oxygen from air than mine for minerals underground.
antialias_physorg
3.5 / 5 (8) Jul 28, 2016
Tell me, what becomes of CO2 when you remove the carbon?

The system they have doesn't capture the oxygen.
RichManJoe
5 / 5 (2) Jul 28, 2016
I have always used a solar power density of 1000 watts /m^2 . Is this a typo or does it truly require 10 times less power.
Whydening Gyre
4.5 / 5 (8) Jul 28, 2016
The economy and environmental footprint of these expensive academical nonsenses is disputable from their very beginning.

That's always the case in the beginning. Scale it up and see what happens...
Whydening Gyre
4.4 / 5 (7) Jul 28, 2016
you have to have oxygen to burn that fuel again.


Tell me, what becomes of CO2 when you remove the carbon?

A fancy air-freshener?
(Not too loud - Dyson might use it to purify your home atmosphere...)
Phys1
4.4 / 5 (7) Jul 28, 2016
As concerns having to carry around oxygen, you may want to do that anyway for breathing.
On Mars there is no free oxygen and this technology can produce it.
Phys1
4.6 / 5 (11) Jul 28, 2016
/* nano-structured compounds ... unconventional ionic liquid ... nanoflake tungsten diselenide */

How long such a thingies survive, before they completely degrade at sunlight, atmospheric humidity and oxygen? How much electricity it actually consumes?

I guess you missed the point. None.

/* Any bets that this technology never sees the light of day again? */

The economy and environmental footprint of these expensive academical nonsenses is disputable from their very beginning.

Spoken like a true visionary.
"All new technologies are nonsense, it's never going to work."
kochevnik
2 / 5 (8) Jul 28, 2016
"When light of 100 watts per square meter - about the average intensity reaching the Earth's surface"

Direct sunlight gives about 900watts/m^2
DonGateley
5 / 5 (1) Jul 28, 2016
This is the one. This spells liberation and gives the space for fully practical nuclear, and I pray (which is not my habit) that there is nothing to keep it from full scale use. Soon.
gkam
2.5 / 5 (13) Jul 28, 2016
Tell me, what becomes of CO2 when you remove the carbon?
---------------------------------------

O2
Da Schneib
4.6 / 5 (10) Jul 28, 2016
Looks pretty good. Turning atmospheric CO2 into syngas will put the carbon into the fuel cycle instead of into the atmosphere.
Whydening Gyre
4.5 / 5 (8) Jul 28, 2016
Looks pretty good. Turning atmospheric CO2 into syngas will put the carbon into the fuel cycle instead of into the atmosphere.

One problem ( on earth, anyway) - what happens if we run out of CO2?
And with all that extra oxygen in the air, stuff will burn better...:-)
mikael_murstam
5 / 5 (2) Jul 28, 2016
it may prove useful on Mars

Not sure about that. While you can probably get some fuel out of the (very thin) CO2 atmosphere you have to have oxygen to burn that fuel again.

As the famous last words of some unsung SciFi roleplayer go:
"We take our flamers, go down to the planet and torch the alien queen!....Whaddaya mean 'no oxygen in the atmosphere'?"


It produces oxygen.
big_hairy_jimbo
5 / 5 (3) Jul 28, 2016
Well this device would certainly be suitable on Mars. But keep in mind the H2 production requires WATER. So not sure you'd want to use up valuable water on Mars to make FUEL from it. However if you closed the cycle and had this machine hooked up to storage, then hooked up to a fuel cell, you have excellent power generation and storage. Would be worth using Martian water if the system is a closed circuit. (all depends on how much water is on Mars)
Mars light intensity also seems favourable with minimum Solar radiation being 492 W/m2 (according to Wiki). I think this device will definitely come in handy :-)
Wonder how it would go with solar concentrators. What affect does temperature have on the system?
wolfdaddy74701
3 / 5 (4) Jul 29, 2016
I've been hearing about nanotube research in this area out of the University of Pennsylvania, but I guess theirs used the gummy, expensive catalysts discussed here. When they have a system that is reliable and cheap enough to go on my roof to power a 5 kw generator all day, that's when I'll get excited.
rrrander
1.5 / 5 (8) Jul 29, 2016
How much of the Earth's surface would need to be covered with these solar cells to create enough of this fuel to replace the billions of gallons of liquid and gas fuel used today? The catalyst might be cheap, but making the solar cells isn't.
antialias_physorg
3.5 / 5 (8) Jul 29, 2016
As concerns having to carry around oxygen, you may want to do that anyway for breathing.
On Mars there is no free oxygen and this technology can produce it.

That's the twist:
Either you use this for producing oxygen for breathing purposes - in which case the entire hydrocarbon fuel part is a waste since you have no oxygen left to burn it..or must implement yet another process to create oxygen so that you can burn this stuff.

Creating oxygen is something we'd want to do on Mars. But I'm fairly certain that if we drop the entire 'hydrocarbon fuel' angle from the design specs of a system that there is some more efficient way to do it.

Hydrocarbon fuels are also very inefficient when burned. Going for a closed hydrogen/oxygen-H2O fuelcell cycle (or just batteries) seems a lot more efficient use of solar power for moving stuff about.
greenonions
4.3 / 5 (6) Jul 29, 2016
rrander
How much of the Earth's surface would need to be covered with these solar cells
Oh not too much http://www.techin...h-2015-9
And of course - we have wind; geothermal; wave; tidal; hydro; otec; nuclear; bio-fuels; conservation etc. etc. etc.
Phys1
4 / 5 (4) Jul 29, 2016
As concerns having to carry around oxygen, you may want to do that anyway for breathing.
On Mars there is no free oxygen and this technology can produce it.

That's the twist:
Either you use this for producing oxygen for breathing purposes - in which case the entire hydrocarbon fuel part is a waste since you have no oxygen left to burn it..or must implement yet another process to create oxygen so that you can burn this stuff.

Creating oxygen is something we'd want to do on Mars. But I'm fairly certain that if we drop the entire 'hydrocarbon fuel' angle from the design specs of a system that there is some more efficient way to do it.

Hydrocarbon fuels are also very inefficient when burned. Going for a closed hydrogen/oxygen-H2O fuelcell cycle (or just batteries) seems a lot more efficient use of solar power for moving stuff about.

Water is another limitation. In the end you will convert O2 into CO2 by breathing so CO2 needs to be recovered .
Eikka
5 / 5 (3) Jul 29, 2016
Either you use this for producing oxygen for breathing purposes - in which case the entire hydrocarbon fuel part is a waste since you have no oxygen left to burn it..or must implement yet another process to create oxygen so that you can burn this stuff.


Getting oxygen is not going to be very hard - it's everywhere around. Take for example, what is sand? SiO2

Producing metals out of the martian soil is going to give you a big waste stream of oxygen anyways because the mineral ores are all oxides. Plain rock is full of oxygen. Getting nitrogen for breathable air is going to be the bigger problem.

Carbon pulled from the atmosphere is also useful for chemically reducing the metals from their ores.
Eikka
5 / 5 (4) Jul 29, 2016
Besides, you're going to be growing food on Mars for the colony anyways, and what do plants do? They release oxygen.

BongThePuffin
Jul 29, 2016
This comment has been removed by a moderator.
gkam
1.3 / 5 (7) Jul 29, 2016
Take the C out of CO2.

I used an eraser.

How would you do it?
Whydening Gyre
4.2 / 5 (5) Jul 29, 2016
gkam 3 /5 (6) 19 hours ago
Tell me, what becomes of CO2 when you remove the carbon?
---------------------------------------

O2


That's pretty naive. It depends how you remove the carbon.


What you actually get is 2 ea. Oxygen atoms... (No carbon to bind them)

And George - that last ba-dmp-bmp was pretty lame...:-)
Whydening Gyre
4.2 / 5 (5) Jul 29, 2016
Producing metals out of the martian soil is going to give you a big waste stream of oxygen anyways because the mineral ores are all oxides. Plain rock is full of oxygen. Getting nitrogen for breathable air is going to be the bigger problem.

My reference for this is the 1st "Total Recall"...:-)
gkam
1 / 5 (5) Jul 29, 2016
"And George - that last ba-dmp-bmp was pretty lame...:-)"

Yeah, . . .
Phys1
3 / 5 (2) Jul 30, 2016
Either you use this for producing oxygen for breathing purposes - in which case the entire hydrocarbon fuel part is a waste since you have no oxygen left to burn it..or must implement yet another process to create oxygen so that you can burn this stuff.


Getting oxygen is not going to be very hard - it's everywhere around. Take for example, what is sand? SiO2

Producing metals out of the martian soil is going to give you a big waste stream of oxygen anyways because the mineral ores are all oxides. Plain rock is full of oxygen. Getting nitrogen for breathable air is going to be the bigger problem.

Carbon pulled from the atmosphere is also useful for chemically reducing the metals from their ores.

If you have to produce silicon in order to breathe you have a big problem :-) .
Eikka
5 / 5 (2) Jul 30, 2016
If you have to produce silicon in order to breathe you have a big problem :-) .


The oxygen is not consumed by breathing it. It returns as CO2 which is recycled back by the plants used to make all the food the population eats. For a given population of people, you will only need to add a certain amount of oxygen once and then simply replace what leaks out.

The oxygen gained from minerals and metals extraction is surplus. Same as with pulling CO2 out of the atmosphere to turn it into fuel - the oxygen released on the side is surplus and free to use to later oxidize the fuel for energy.
Phys1
3.7 / 5 (3) Jul 30, 2016
@Eikka
That is how it is on Earth. What makes you think it is viable to grow plants on Mars just for the sake of producing oxygen ? It will take a lot more than you can eat.
Eikka
3.7 / 5 (3) Jul 31, 2016
@Eikka
That is how it is on Earth. What makes you think it is viable to grow plants on Mars just for the sake of producing oxygen ? It will take a lot more than you can eat.


How do you think of having a colony on mars if you can't grow your own food there? It's pretty much assumed you can, or you won't be going there anyhow because the logistics of continuous supply from earth is just too damn expensive.

Growing enough food for you to eat releases exactly the amount of oxygen needed for you to metabolize that same food, and there will actually be an excess of oxygen because parts of the plants are inedible. The excess carbon and oxygen have to be burned to keep enough CO2 in the system for the plants to grow.

tear88
5 / 5 (1) Jul 31, 2016
Any bets that this technology never sees the light of day again?

I had a similar reaction on reading "The finding ... was funded by the National Science Foundation and the U.S. Department of Energy. A provisional patent application has been filed.".

Any patent should give EVERYONE the right to use the technology.

There's something similar going on with the DeVAP HVAC technology; controlled by the government, with no visible progress in rollout.
tear88
5 / 5 (1) Jul 31, 2016
"uses sunlight to remove CO2 from the atmosphere and produce burnable fuel"
Isn't that what trees do?

What are these "trees" of which you speak? Oh, wait, I think I saw one recently. In a museum.

I wonder which process is a) more environmentally friendly and b) faster. Who knows, maybe we can erect roofs equipped with this new invention, over the parking lots.
PoppaJ
4 / 5 (4) Jul 31, 2016
I love this!!!! I am involved in Auto sports. This will allow us to run 1000 Hp machines that are co2 Neutral. Where the hell is my 9 mpg V8 Big block.
aksdad
1.8 / 5 (5) Aug 01, 2016
Any word on efficiency? There's not much CO2 in the air. It only makes up 0.04% of the atmosphere (400 parts per million). There was this statement:

The ability to turn CO2 into fuel at a cost comparable to a gallon of gasoline would render fossil fuels obsolete.

But it didn't say this method could actually do it, or even has the potential to do it, at a cost comparable to manufacturing gasoline from oil.

Phys1
1 / 5 (1) Aug 01, 2016
@Eikka
How do you think of having a colony on mars if you can't grow your own food there?

How did you get the idea that I think this?
Dug
3.7 / 5 (3) Aug 01, 2016
While this is significant research, it's assumptions show a severe lack of economic understanding when making the following statement:

"The ability to turn CO2 into fuel at a cost comparable to a gallon of gasoline would render fossil fuels obsolete."

There's and economic catch here. The source of ethyl-methyl-imidazolium tetrafluoroborate is... wait for it... the petro-chemical industry. The petro-chemical industry (about 5% of the total petroleum industry) is economically dependent on the economy-of-scale of the petroleum industry. The bulk of the petroleum industry is transportation and heating fuels. Doing away with petroleum fuels while great for the environment will have huge down stream economic/cost increase impacts on the petro-chemical industry including food production, pharma, plastics and the synthesis of ethyl-methyl-imidazolium tetrafluoroborate. So, like biofuels it turns out the process to get rid of petroleum is also economically dependent on the petroleum.
greenonions
3 / 5 (2) Aug 01, 2016
Dug
it's assumptions show a severe lack of economic understanding
Not at all. The reason there is so much pain the the ff industries right now - is because the price being paid for ff, is not allowing companies to run at a profit. So - if oil is selling at $40 a barrel - and oil companies can't make money at the cost - and this process (even using ff as part of the process) can make fuel at less than $40 a barrel - you change the whole dynamic - and ff becomes obsolete as a primary fuel source. Of course - there is a massive competition going on right now - and renewable from wind and solar looks poised to win that one - as the costs just keep falling. http://renewecono...ee-27165
ka_
4 / 5 (1) Aug 01, 2016
What about capturing the carbon right from the exhaust of a car rather than the atmosphere?
humy
3.2 / 5 (5) Aug 02, 2016
Any bets that this technology never sees the light of day again?

yes.
This is because making hydrogen biofuel is a deeply flawed strategy and only in part because each molecule of H2 leaked into the atmosphere, and there would inevitably be wide spread leakage if the so called "hydrogen economy" is ever realized, has many time the greenhouse effect as each molecule of CO2.
If the whole point of this is to stop global warming, its a non-starter.
Plus efficient compact H2 storage is a major issue.
Plus it is unsafe as it easily explodes if accidental mixed with air in an accident; -you certainly wouldn't want your cars to store H2 in a car pile up!
Much better to stick to other types of renewables.
ka_
4 / 5 (1) Aug 02, 2016
If this production could be made in a small scale such as in a car, and then used almost as soon as it is produced, then you would likely not need to store a lot of it. I would assume we in this case still should see a substantial reduction in emission.
DonGateley
4.5 / 5 (2) Aug 02, 2016
At the largest scale here we have usable knobs on the CO2/O2 content of the atmosphere and probably a lot of chemistries. Who will decide on the real time setting of those knobs? Better settle that up front.

If it's done locally all kinds of new cycles and dynamics could ensue and we won't be any better off than we were. If even.
lengould100
5 / 5 (1) Aug 03, 2016
humy - You (and several others here) appear to be just completely off-base-negative on this.

"Hydrogen storage in cars is a problem"? Reliable reference please. Most recent tests I've seen results for have proven that stored hydrogen is no more explosive than gasoline, and when the tank is breached (needed a 50 cal. rifle to do it) the hydrogen just leaks straight up, damaging pretty much nothing, whereas gasoline fro a ruptured fuel tank flows down under the vehicle, just waiting to cook the occupants.

All your rest the same.

Invest in oil much?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.