Scientists solve puzzle of converting gaseous carbon dioxide to fuel

August 25, 2016
Converting greenhouse gas emissions into energy-rich fuel using nano silicon (Si) in a carbon-neutral carbon-cycle is illustrated. Credit: Chenxi Qian

Every year, humans advance climate change and global warming - and quite likely our own eventual extinction - by injecting about 30 billion tonnes of carbon dioxide into the atmosphere.

A team of scientists from the University of Toronto (U of T) believes they've found a way to convert all these emissions into energy-rich fuel in a carbon-neutral cycle that uses a very abundant natural resource: silicon. Silicon, readily available in sand, is the seventh most-abundant element in the universe and the second most-abundant element in the earth's crust.

The idea of converting to energy isn't new: there's been a global race to discover a material that can efficiently convert sunlight, carbon dioxide and water or hydrogen to fuel for decades. However, the of carbon dioxide has made it difficult to find a practical solution.

"A chemistry solution to requires a material that is a highly active and selective catalyst to enable the conversion of carbon dioxide to fuel. It also needs to be made of elements that are low cost, non-toxic and readily available," said Geoffrey Ozin, a chemistry professor in U of T's Faculty of Arts & Science, the Canada Research Chair in Materials Chemistry and lead of U of T's Solar Fuels Research Cluster.

In an article in Nature Communications published August 23, Ozin and colleagues report silicon nanocrystals that meet all the criteria. The hydride-terminated silicon nanocrystals - nanostructured hydrides for short - have an average diameter of 3.5 nanometres and feature a surface area and optical absorption strength sufficient to efficiently harvest the near-infrared, visible and ultraviolet wavelengths of light from the sun together with a powerful chemical-reducing agent on the surface that efficiently and selectively converts gaseous to gaseous carbon monoxide.

The potential result: energy without harmful emissions.

"Making use of the reducing power of nanostructured hydrides is a conceptually distinct and commercially interesting strategy for making fuels directly from sunlight," said Ozin.

The U of T Solar Fuels Research Cluster is working to find ways and means to increase the activity, enhance the scale, and boost the rate of production. Their goal is a laboratory demonstration unit and, if successful, a pilot solar refinery.

Explore further: Keeping captured carbon dioxide in liquid makes it more reactive and easier to concentrate

More information: Wei Sun et al, Heterogeneous reduction of carbon dioxide by hydride-terminated silicon nanocrystals, Nature Communications (2016). DOI: 10.1038/ncomms12553

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Tenstats
2 / 5 (6) Aug 25, 2016
Sigh, here we go again. Convert CO2 to CO to make a fuel. Burn the fuel and out comes the same CO2. I wish the reviewer as well as the authors of the paper would quit invoking the concept of reducing CO2 emissions when CO2 is converted into a fuel that is burned again.
Eikka
4.6 / 5 (11) Aug 25, 2016
I wish the reviewer as well as the authors of the paper would quit invoking the concept of reducing CO2 emissions when CO2 is converted into a fuel that is burned again.


There's no net emissions if you keep using the same CO2 over and over.
Manfred Particleboard
3.7 / 5 (3) Aug 25, 2016
It's implied that closing the carbon cycle by using a solar reforming process eliminates the need for fossil fuels (in a significant way). Without the pump and dump model, emissions will reduce. But the wording could be more clear about the way emissions would be neutral rather than escalating.
skedaddlehop
3.3 / 5 (3) Aug 25, 2016
If you need sunlight to make the process work, then just use solar panels and a battery bank. Energy without harmful emissions. Why go exotic?
TheKnowItAll
3 / 5 (2) Aug 25, 2016
The way it is presented one could think that they are actually converting the existing emission which would reduce the level of CO2 from the atmosphere but since the released CO goes back up in the atmosphere and is converted automatically back into CO2 there is no reduction at all other than oxygen. Or am I missing something?
szore88
1.8 / 5 (11) Aug 25, 2016
"Man made global warming"? Even tho we have records going back 100,000 years showing climate change, the Marxists still push this scam to confiscate private wealth. Pathetic.
Eikka
3 / 5 (2) Aug 26, 2016
If you need sunlight to make the process work, then just use solar panels and a battery bank. Energy without harmful emissions. Why go exotic?


The batteries are the "exotic". They need rare and expensive elements, a lot of energy to make, and they break down in just a few years.

CO2 derived fuels are more useful and higher value because they also act as chemical precursors to plastics and other useful materials such as drugs, dyes, explosives and fertilizers etc.

It's hard to turn electricity from a battery into a useful fuel for a dump truck that has to do actual work because the energy density is too low.
antialias_physorg
not rated yet Aug 26, 2016
If you need sunlight to make the process work, then just use solar panels and a battery bank. Energy without harmful emissions. Why go exotic?

Because a solar panel and a battery won't move a ship accross the ocean (yet).
Not saying that this is preferrable. I'd prefer if shipping was changed over to hydrogen as a fuel. But the reality is that a lot of the ships that are currently carrying goods will be in service for some time to come. Having them fueled from a carbon neutral source would be one step in the right direction.

But that's the catch. This isn't going to enable a carbon neutral economy: The reaction takes place in a 99.9% CO2 atmosphere (see linked article). Since no current combustion source captures its CO2 exhaust... you get the idea.
Eikka
not rated yet Aug 26, 2016
I'd prefer if shipping was changed over to hydrogen as a fuel.


Liquefied methane goes a lot further, and it's a free refridgerant for the cargo.

And it's easily manufactured from CO2.

The reaction takes place in a 99.9% CO2 atmosphere (see linked article). Since no current combustion source captures its CO2 exhaust... you get the idea.


Capturing CO2 from the atmosphere isn't actually prohibitively difficult. It's just more expensive than pulling it out of smokestacks.
Eikka
1 / 5 (1) Aug 26, 2016
One great way to get CO2 is by burning biomass and waste for energy, which gives you a concentrated CO2 stream, which can then be turned into transportation fuels with other renewable energy.

A great deal of fossil fuels are used for heating buildings, with people burning natural gas in furnaces and boilers. Replacing those with district heating systems allows for a closed cycle where the CO2 is collected and recycled back to be re-made into the fuels that power the district heating plants.

In fact the gas grid is the biggest battery. There's about 200 TWh worth of gas in the EU gas grid, just in the pipes.
barakn
4 / 5 (4) Aug 26, 2016
"Man made global warming"? Even tho we have records going back 100,000 years showing climate change, the Marxists still push this scam to confiscate private wealth. Pathetic. -szore88

The usual denier strawman argument. No one is arguing that climate hasn't changed on geological time scales or isn't capable of changing without human intervention. The actual issue is the rate of change. Rate is a mathematical concept and I know many of you are bad at math, but it's never too late to go back to school.
Phys1
1 / 5 (1) Aug 26, 2016
A few of those cells on the roof to fill'r up every day would be welcome.
antialias_physorg
5 / 5 (1) Aug 26, 2016
A few of those cells on the roof to fill'r up every day would be welcome.

I dunno. You got 99.9% CO2 at more than double atmospheric pressure on your roof?
Phys1
5 / 5 (1) Aug 28, 2016
A few of those cells on the roof to fill'r up every day would be welcome.

I dunno. You got 99.9% CO2 at more than double atmospheric pressure on your roof?

No I don't. I need a little extra thingy to overcome that.
tinitus
Aug 28, 2016
This comment has been removed by a moderator.
SURFIN85
1 / 5 (1) Aug 29, 2016
CO2(g) + Si(s) -> CO(g) + SiO(s)

CO(g) + 2CaOH(l) -> CaCO3(s)

What am I missing (Besides my copy of Marx's Communist Manifesto)
bruenor
not rated yet Aug 29, 2016
Trees do a remarkably good job converting C02 to useful carbon, not that the result isn't interesting for areas like deserts where there is not a lot of bio-activity, and CO can be turned into interesting compounds with enough additional energy.
As a counter intuitive thought, incomplete combustion of wood produces charcoal which takes thousands of years to decompose. Not talking slash and burn here but I haven't spotted the flaw in turning waste wood into charcoal or specifically growing wood and converting it to charcoal (producing energy) as a carbon sink.
nrauhauser
not rated yet Sep 11, 2016
Sigh, here we go again. Convert CO2 to CO to make a fuel. Burn the fuel and out comes the same CO2. I wish the reviewer as well as the authors of the paper would quit invoking the concept of reducing CO2 emissions when CO2 is converted into a fuel that is burned again.


Perfect is the enemy of good. If we get two uses out of a C atom before it ends up as CO2, that's a 100% improvement. We also get some new tech getting there, and maybe a step towards political willingness to tax carbon. We aren't going to flip to solar/wind/conservation/magic fusion improvement overnight.
nrauhauser
not rated yet Sep 11, 2016
The in-situ reduction of CO2 into a carbon monoxide is extremely impractical, because the collection and distribution of gases with pipes is always more expensive than the distribution of electricity (and this is always more expensive, than the production/consumption of energy at place). It's much cheaper to utilize the solar electricity (which comes in http://energytran...2015.png with no utility value) for conversion of carbon dioxide into a fuel at dedicated plants, preferably close to fossil-fuel plants, which are largest producers of carbon dioxide in relatively pure form.


There is much value in making CO, which can be stored for later use, transported, etc.

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