Energy

Solar cell sucks up CO2 and spits burnable fuel out the other side

The solar cell  converts atmospheric carbon dioxide directly into syngas, using light for energy
The solar cell  converts atmospheric carbon dioxide directly into syngas, using light for energy
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Amin Salehi-Khojin (left), UIC assistant professor of mechanical and industrial engineering, and postdoctoral researcher Mohammad Asadi with their breakthrough solar cell 
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Amin Salehi-Khojin (left), UIC assistant professor of mechanical and industrial engineering, and postdoctoral researcher Mohammad Asadi with their breakthrough solar cell 
The solar cell  converts atmospheric carbon dioxide directly into syngas, using light for energy
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The solar cell  converts atmospheric carbon dioxide directly into syngas, using light for energy

Recreating a plant's ability to use sunlight to turn carbon dioxide into fuel, something known as artificial photosynthesis, is one of the holy grails of green energy research. Researchers have now edged closer toward this dream technology, developing what they describe as a game-changing solar cell that produces hydrocarbon fuels in the lab, with potential applications ranging from large-scale uses on Earth to providing power on Mars.

The prospect of using sunlight to power our energy-intensive lifestyles has enough merit on its own, but what if we could suck carbon dioxide out of the atmosphere while we're at it? This two-pronged environmental panacea has inspired scientists eyeing a greener future, with artificial leaves, hybrid energy systems and moth-inspired photoelectrochemical cells just a few examples of how we are progressing toward this goal.

Scientists at Chicago's University of Illinois have been working with new kinds of chemicals with new kinds of properties to take these efforts to the next level. The key, they say, is to discover a new type of catalyst that can turn atmospheric CO2 into burnable fuels in an efficient and inexpensive way.

In pursuit of this, the team was working with a set of nanostructured compounds called transition metal dichalcogenides, or TMDCs. It happened upon one TMDC called nanoflake tungsten diselenide which, when paired with water and a particular ionic liquid as the electrolyte, worked 1,000 times faster than the expensive metals usually used in these CO2 reduction technologies. The fact that it is about 20 times cheaper didn't hurt either.

"The active sites of the catalyst get poisoned and oxidized," says Amin Salehi-Khojin, senior author on the study. "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."

The solar cell itself is made up of two silicon triple-junction photovoltaic cells measuring 18 cm sq (2.8 in sq) to harvest the light, with the co-catalyst system on the cathode side and cobalt oxide in potassium phosphate electrolyte on the anode side.

When 100 W of light per meter squared hits the cell, it kicks off a chemical reaction where hydrogen and carbon monoxide gas are produced from the cathode. Free oxygen and hydrogen ions are generated at the anode. This reaction creates synthesis gas, or syngas, which can be burned as is or turned into diesel and other hydrocarbon fuels.

According to the team, the solar cell could be adapted to large-scale use such as solar farms, along with smaller applications. One day, it might even provide power on Mars if water can be found there, as the planet's atmosphere is largely carbon dioxide.

"The new solar cell is not photovoltaic — it's photosynthetic," says Salehi-Khojin. "Instead of producing energy in an unsustainable one-way route from fossil fuels to greenhouse gas, we can now reverse the process and recycle atmospheric carbon into fuel using sunlight."

The research was published in the journal Science.

Source: University of Illinois

19 comments
Mzungu_Mkubwa
Cool, enviro-friendly gas! [turns around, pours fuel into gas tank, starts up engine] Oops! What's that coming out of the exhaust pipe? CO and CO2? Bummer! Sorry, Earth. Gotta have my ride, after all, right?
Digitalclips
This is awesome as long as you don't then actually use the hydrocarbons. If you use them as an energy source you just two steps forward and two steps back! If the hydrocarbons are somehow taken out of the loop then great, go for it.
Fretting Freddy the Ferret pressing the Fret
@MuznguMkubwa @Digitalclips Both of you don't understand that if hydrocarbons were produced from this renewable syngas and subsequently burned, there is no net change in atmospheric CO2 levels. Mainstream media has pounded into your heads that hydrocarbons are bad by definition. Hydrocarbons are only bad news if we extract it from the ground and burn it, so the net CO2 levels does change.
Galymax
This would actually be a sustainable energy source as long as you don't burn any additional hydrocarbons extracted from the ground. You just recapture the CO2 you release while burning the fuel so the CO2 level in the atmosphere stays the same over time. The only problem would be with heath effects caused by byproducts of burning it.
Wolf0579
We must get away from this primitive idea of burning everything. It creates even more waste heat in a world with an abundance of heat.
PeterMortensene7877c8e180f4d2a
If we could use that hydrocarbon to make plastic or other products trapping the carbon, it would be great. The future is DEFINITELY not in keep burning gas in combustion engines we drive in our local environments resulting in cancer causing hydrocarbons right at nose height.
VirtualGathis
@Digitalclips - I think you missed the idea behind this entirely. This is not an atmospheric co2 elimination technique, it is a carbon neutral way of providing energy storage and fuel. The idea here is that less-than or equal-to co2 is emitted when the fuel is burned, which is vastly preferable to burning NG and fossil fuels which does nothing to provide for removal of the carbon form the atmosphere. It is also a way to reduce fossil fuel dependence and thus reduce foreign influence on the hosts economy. If the materials can be sourced locally or at least within the host nation it could serve to help stabilize that nations economy. This is all assuming it can be scaled effectively and affordably of course. These kinds of things seem to be notoriously hard to commercialize.
rpark
...need oxygen to burn the 'synfuel' resulting in even more CO2 end product after combustion ?
EternityDeep
This is great news. Science will eventually solve the crisis of CO2. I look forward to the day when this technology is positioned at the exit of every new power plant. Time to invest in these kinds of technologies. Remove the tax breaks for the fossil fuel industry and move it to the green energy industry.
AndrewThompson
Fantastic bit of science to use one result to perhaps solve two problems. However, what is really disappointing is the fact that the governor of Illinois has cut the U of Illinois's funding along with all of the other Illinois public universities [i.e. last year there was no budgeted amount of any of them]. This is a perfect example of why the governor of Illinois is so, so short sighted in trying to tear down and dismantle higher education in his state --
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