Converting CO2 into usable energy

Converting CO2 into usable energy
Brookhaven scientists are pictured at NSLS-II beamline 8-ID, where they used ultra-bright x-ray light to 'see' the chemical complexity of a new catalytic material. Pictured from left to right are Klaus Attenkofer, Dong Su, Sooyeon Hwang, and Eli Stavitski. Credit: Brookhaven National Laboratory

Imagine if carbon dioxide (CO2) could easily be converted into usable energy. Every time you breathe or drive a motor vehicle, you would produce a key ingredient for generating fuels. Like photosynthesis in plants, we could turn CO2 into molecules that are essential for day-to-day life. Now, scientists are one step closer.

Researchers at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory are part of a scientific collaboration that has identified a new electrocatalyst that efficiently converts CO2 to carbon monoxide (CO), a highly energetic molecule. Their findings were published on Feb. 1 in Energy & Environmental Science.

"There are many ways to use CO," said Eli Stavitski, a scientist at Brookhaven and an author on the paper. "You can react it with water to produce energy-rich hydrogen gas, or with hydrogen to produce useful chemicals, such as hydrocarbons or alcohols. If there were a sustainable, cost-efficient route to transform CO2 to CO, it would benefit society greatly."

Scientists have long sought a way to convert CO2 to CO, but traditional electrocatalysts cannot effectively initiate the reaction. That's because a competing reaction, called the hydrogen evolution reaction (HER) or "water splitting," takes precedence over the CO2 conversion reaction.

A few noble metals, such as gold and platinum, can avoid HER and convert CO2 to CO; however, these metals are relatively rare and too expensive to serve as cost-efficient catalysts. So, to convert CO2 to CO in a cost-effective way, scientists used an entirely new form of catalyst. Instead of noble metal nanoparticles, they used single atoms of nickel.

"Nickel metal, in bulk, has rarely been selected as a promising candidate for converting CO2 to CO," said Haotian Wang, a Rowland Fellow at Harvard University and the corresponding author on the paper. "One reason is that it performs HER very well, and brings down the CO2 reduction selectivity dramatically. Another reason is because its surface can be easily poisoned by CO molecules if any are produced."

Single atoms of nickel, however, produce a different result.

"Single atoms prefer to produce CO, rather than performing the competing HER, because the surface of a bulk metal is very different from ," Stavitski said.

Klaus Attenkofer, also a Brookhaven scientist and a co-author on the paper, added, "The surface of a metal has one energy potential—it is uniform. Whereas on a single atom, every place on the surface has a different kind of energy."

In addition to the unique energetic properties of single atoms, the CO2 conversation reaction was facilitated by the interaction of the nickel atoms with a surrounding sheet of graphene. Anchoring the atoms to graphene enabled the scientists to tune the catalyst and suppress HER.

To get a closer look at the individual nickel atoms within the atomically thin graphene sheet, the scientists used scanning transmission electron microscopy (STEM) at Brookhaven's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility. By scanning an electron probe over the sample, the scientists were able to visualize discrete nickel atoms on the graphene.

"Our state-of-art transmission electron microscope is a unique tool to see extremely tiny features, such as single atoms," said Sooyeon Hwang, a scientist at CFN and a co-author on the paper.

"Single atoms are usually unstable and tend to aggregate on the support," added Dong Su, also a CFN scientist and a co-author on the paper. "However, we found the individual nickel atoms were distributed uniformly, which accounted for the excellent performance of the conversion reaction."

To analyze the chemical complexity of the material, the scientists used beamline 8-ID at the National Synchrotron Light Source II (NSLS-II)—also a DOE Office of Science User Facility at Brookhaven Lab. The ultra-bright x-ray light at NSLS-II enabled the scientists to "see" a detailed view of the material's inner structure.

"Photons, or particles of light, interact with the electrons in the nickel atoms to do two things," Stavitski said. "They send the electrons to higher energy states and, by mapping those energy states, we can understand the electronic configuration and the chemical state of the material. As we increase the energy of the photons, they kick the electrons off the atoms and interact with the neighboring elements." In essence, this provided the scientists with an image of the nickel atoms' local structure.

Based on the results from the studies at Harvard, NSLS-II, CFN, and additional institutions, the scientists discovered single catalyzed the CO2 conversion reaction with a maximal of 97 percent efficiency. The scientists say this is a major step toward recycling CO2 for and chemicals.

"To apply this technology to real applications in the future, we are currently aimed at producing this single atom catalyst in a cheap and large-scale way, while improving its performance and maintaining its efficiency," said Wang.


Explore further

Study of graphene catalysts finds metal in 'metal-free' catalysts

More information: Kun Jiang et al, Isolated Ni single atoms in graphene nanosheets for high-performance CO2 reduction, Energy & Environmental Science (2018). DOI: 10.1039/C7EE03245E
Journal information: Energy & Environmental Science

Citation: Converting CO2 into usable energy (2018, March 1) retrieved 21 July 2019 from https://phys.org/news/2018-03-co2-usable-energy.html
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Mar 02, 2018
"...Imagine if carbon dioxide (CO2) could easily be converted into usable energy. ..."

Stop right there; CO2 is NOT a source of energy. You can convert it into some sort of fuel that can then be used as a source of energy, sure. But, because of the laws of thermodynamics, you can only do that by using up at least as much energy to make that fuel than you can possibly get out of it (actually less than that because of losses). And if the source of energy for that fuel-making process is fossil fuels, that would make the whole process completely pointless.
They haven't thought this through at all.

Now, if they were speaking about taking CO2 straight out from the wider atmosphere and then converting THAT into fuel using electricity specifically from carbon-neutral sources (nuclear and/or renewables), they might be on to something. But, sadly, that isn't what they are saying here.

Mar 02, 2018
When are the global warming kooks going to give up on this nonsense? It'll cost a fortune to develop and processes this. Hydrogen will never be cracked out of water cheaply. Algae will never produce ethanol or biodiesel at an economical level. Enough with this stuff.

Mar 02, 2018
Stop right there; CO2 is NOT a source of energy.


Stop right there. Irrelevant complaint.

Converting CO2 into a fuel is an answer to the question, where to get gasoline, oils, plastics, fertilizers, chemicals, drugs etc. in a world where you can't dig out more petroleum out of the ground anymore.

It doesn't matter where the energy comes from, that you indeed do need energy, because various options exist and the important bit is making the process work well enough to be relevant.

Mar 02, 2018
Stop right there; CO2 is NOT a source of energy.


Stop right there. Irrelevant complaint

Why?

Converting CO2 into a fuel is an answer to the question, where to get gasoline, oils, plastics, fertilizers, chemicals, drugs etc. in a world where you can't dig out more petroleum out of the ground anymore.


This link doesn't speaks of extracting CO2 DIRECTLY from the wider atmosphere so presumably they are thinking of extracting it directly from the exhausts. How would that work for a gasoline-fuelled car? Even if it was from the exhausts from a stationary power station, that wouldn't make much sense. WHERE would the energy come from to convert the CO2 into fuel? From burning the same fuel that was used to make that CO2? -that would break the laws of thermodynamics because there would be energy losses (unused waste heat) from that cycle that would mean you would end up with less usable energy than you put in into each cycle; you make no sense.

Mar 02, 2018
When are the global warming kooks going to give up on this nonsense? It'll cost a fortune to develop and processes this. Hydrogen will never be cracked out of water cheaply. Algae will never produce ethanol or biodiesel at an economical level. Enough with this stuff.

Although I would totally agree with you that the concepts of using (in those particular ways) hydrogen and algae are deeply flawed and highly impractical and could even be counterproductive, what about wind, hydroelectric, nuclear etc power? Generating power from, say, hydroelectric, isn't just complete "nonsense", right?

Mar 02, 2018
"You can react it with water to produce energy-rich hydrogen gas

Which releases CO2 in the process...soooo: Where again is the benefit?

Imagine if carbon dioxide (CO2) could easily be converted into usable energy

Really only makes sense if you have some disposable energy source that drives this (i.e. energy from a source that you'd otherwise throw away). Otherwise it's always more efficient to just use that energy directly as a 'fuel' (in batteries or whatnot) instead of converting it to a carbohydrate and then burning these at an atrociously low efficiency rate.

CO2 is the END-product of combustion for a reason: because it is a very low energy molecule. To make some use of it as a precursor of a fuel energy has to be pumped in (because the end result of the burnt fuel will be CO2 again. If no energy were needed then you'd just have invented a pertpetuum mobile)


Mar 02, 2018
"Stop right there. Irrelevant complaint."

Eikka I am surprised at you. The only source of reasonably concentrated CO2 is fossil power plants and when we run short of fossil fuels they will be the first to go so where will the CO2 come from? Electricity would have to be free in order for CO2 to become a major player in the fuel mix.

Mar 02, 2018
BTW I am not saying that the science is useless. It can be a major development in catalyst research. Perhaps if the catalyst can be powered by the sun it could be a useful addon to and existing gas powered electric plant by recycling the CO into the fuel mixture. I don't know if the gain in efficiency would exceed the output of solar cells for a given cost.

Mar 02, 2018
Why?


Because it's missing the point.

This link doesn't speaks of extracting CO2 DIRECTLY from the wider atmosphere so presumably they are thinking of extracting it directly from the exhausts. How would that work for a gasoline-fuelled car?


Why would it need to? There are other exhausts.

The only source of reasonably concentrated CO2 is fossil power plants


How about waste incinerators, biofuel burning plants, factories that burn limestone to produce cement (drives off CO2), breweries, biogas fermenting produces tons of CO2...

Really only makes sense if you have some disposable energy source that drives this (i.e. energy from a source that you'd otherwise throw away


Like all the renewable energy that doesn't fit the grids, or the surplus power of nuclear powerplants that are forced to throttle down when the demand is low.

Mar 02, 2018
Besides, liquid fuels are much much more expensive than electricity.

Consider, a gallon of gasoline costs about $3-4 or thereabouts. An equivalent amount of electricity costs about $1.60 to produce with present means. The cost goes down if the powerplants don't need to throttle up and down, or if you can capture the unused surplus of intermittent sources.

In any case, the throughput efficiency from catching the CO2 to turning the electricity into fuels need only be about 45% to break even. That's not very much, and the Fraunhofer institute already has a process and a pilot plant in operation that captures CO2 out of the atmosphere and turns it into methane at 40% efficiency - a cheaper fuel, but not very far off from conversion to gasoline with better catalysts.


Mar 02, 2018
Eikka It is my understanding that the nukes are running at full capacity most of the time and that the gas fired plant take up most of the swing load. Thus the CO2 based fuel produced would be made from natural gas fueled plants. Natural gas is a usable fuel as it is and nothing will be gained by converting its energy to CO at a great loss in efficiency.

Mar 02, 2018
Eikka It is my understanding that the nukes are running at full capacity most of the time


Where nuclear power is in the minority, yes. In France for example, nuclear power is a part of the load following capacity and in the long term runs at partial capacity.

In general, most powerplants run at a capacity factor below 1 for two reasons: load following, and reserve capacity. Sinking all the excess capacity to energy storage would greatly reduce the cost of energy while maintaining the adjustability by adjusting the demand.

This also applies to renewable energy which is forced to run at lower than its maximum capacity factor because of curtailing, because things like solar and wind power have peak capacities up to 10x their average capacity and the peak output is simply lost. Having a huge energy sink like synthetic fuels would allow great expansion of renewables capacities without the excessive cost of superfluous transmission infrastructure.

Mar 02, 2018
Renewable energy in general can be reasonably cheap if all the external costs, like the additional need for load following or extra transmission infrastructure, are solved. Wind power by itself without the externalities is no more expensive than coal or gas power immediately, and saves a whole bunch through diminished pollution.

If there is guaranteed demand, all the power can be sold at real cost, no subsidies needed, and thereby competition would guarantee that the prices remain low. That would realize the true benefit of renewable energy.

This does not happen if the renewable energy is stored directly in batteries, because the worth of the electricity you get out is still less than the electricity and cost you put in. You have to upcycle it into more valuable products, like liquid fuels and chemicals with more value like plastics, solvents, lubricants, drugs, fertilizers, etc.

Mar 02, 2018
And, in fact, IF the societies are to free themselves of fossil fuels, they must develop a system to synthesize all the chemicals and run all the processes that currently run on fossil fuels. Things like building computers out of silicon, which uses carbon to reduce the metal out of its oxides - a process which again makes CO2 which can be recaptured and turned back into the same chemicals used in the process in a closed cycle

Only part of the need for hydrocarbon fuels and chemicals is needed for things like cars, a part which can easily be reduced by a great margin anyhow with application of fuel cells, hybrids, making the CO2 cycle leak less

Which releases CO2 in the process...soooo: Where again is the benefit?


The use of CO in a shift reaction to produce hydrogen produces concentrated CO2 which can be recycled back to CO in a closed cycle. The hydrogen can be used to produce NH4 or ammonia, which is the precursor to nitrogen fertilizers feeding 80% of humanity

Mar 02, 2018
And the beauty of using chemical means like CO instead of other means like electrolysis, is the fact that you don't need to purify the water to such a great extent before you put it in the reactor. The CO reacts with the water, not the salts in the water, so you don't need to consume fresh water or spend enormous amounts of energy to de-salinate water to keep your electrodes from fouling.

The gasworks of the 19th century worked by spraying water over coals, producing hydrogen and methane by the carbon monoxide present in the oxygen starved oven. This gas was pumped around the city to power lights, heaters, engines, factories and homes. Any old water, not de-ionized distilled water, but water you got out of the river Thames however murky it was.


Mar 02, 2018
Well, it's going to have to compete with supercapacitors, new battery tech, new transmission tech, and new fuel source tech. But hey, if it's cheaper and stabler to store a watt for an hour in CO than it is to store it as, say, water in a pumped hydro reservoir, why not?

Mar 03, 2018
If they'd said 'feedstock' instead of 'renewable energy', most of the above arguments become moot...

Mar 04, 2018
Or, as I like to point out: if all the fjords in Norway were harnessed for hydroelectric power storage, it would amount to roughly 80-90 TWh of capacity.

Meanwhile, the continental European gas network with its pipes and gas bells already holds on the order of 200-300 TWh of energy - though that's only couple months of strategic reserve in terms of natural gas consumption.

That's 2,000,000 times more energy than Elon Musk's great big battery in Australia.

That's a great illustration of the scale of the issue, and why electric batteries or hydroelectric dams are not going to solve the issue of renewable energy storage any time soon. Meanwhile, chemical means of storage are already available on a massive scale and the question is about producing the chemicals by efficient means.

Mar 04, 2018
"Or, as I like to point out: if all the fjords in Norway were harnessed for hydroelectric power storage, it would amount to roughly 80-90 TWh of capacity."

And destroy the habitat of the rare and endangered Norwegian ice parrot? Never!

Mar 04, 2018
bill gates just got a heart burn lol

Mar 05, 2018
When are the global warming kooks going to give up on this nonsense? It'll cost a fortune to develop and processes this. Hydrogen will never be cracked out of water cheaply. Algae will never produce ethanol or biodiesel at an economical level. Enough with this stuff.


When? Probably long after your half life decays. You might want to avoid commenting on stuff you know nothing about.

Mar 05, 2018
As a thought experiment, let's take that 200 TWh of energy and split it between approximately 500 million people in Europe. That's 400 kWh per person stored as methane in the pipelines.

That's equivalent to about 12 gallons of gasoline per person.

To store the equivalent amount of energy in Tesla's batteries, each person should buy FOUR Tesla Model S car batteries at a cost of roughly $150,000. Meanwhile, if anyone would like to have 12 gallons of gasoline in their garage for backup, it would cost them about $50 plus $20 for the empty drum, or maybe around $120 at European fuel prices.

THAT is why battery electric storage will never compete. I cannot see how battery prices could drop by a factor of 1000


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