Recycling carbon dioxide: Researchers reduce climate-warming CO2 to building blocks for fuels

August 3, 2016, University of Toronto
U of T Engineering researchers Min Liu (left), Yuanjie Pang and their team designed a way to efficiently reduce climate-warming carbon dioxide into carbon monoxide, a useful chemical building block for fuels such as methanol, ethanol and diesel. Credit: Marit Mitchell, U of T Engineering

Turning carbon dioxide into stored energy sounds like science fiction: researchers have long tried to find simple ways to convert this greenhouse gas into fuels and other useful chemicals. Now, a group of researchers led by Professor Ted Sargent of the University of Toronto's Faculty of Applied Science & Engineering have found a more efficient way, through the wonders of nanoengineering.

Drs. Min Liu and Yuanjie Pang, along with a team of graduate students and post-doctoral fellows in U of T Engineering, have developed a technique powered by renewable energies such as solar or wind. The catalyst takes climate-warming (CO2) and converts it to carbon-monoxide (CO), a useful building block for carbon-based chemical fuels, such as methanol, ethanol and diesel.

"CO2 reduction is an important challenge due to inertness of the molecule," says Liu. "We were looking for the best way to both address mounting global energy needs and help the environment," adds Pang. "If we take CO2 from industrial flue emissions or from the atmosphere, and use it as a reagent for fuels, which provide long-term storage for green energy, we're killing two birds with one stone."

The team's solution is sharp: they start by fabricating extremely small gold "nanoneedles"—the tip of each needle is 10,000 times smaller than a human hair. "The nanoneedles act like lightning rods for catalyzing the reaction," says Liu.

Gold nanoneedle lightening rods concentrate CO2 for reaction: The high curvature nanoneedles produce a high local electric field, as represented by the lightening, which attracts the harmful CO2 gas to the catalyst to be converted into carbon monoxide, a building block for many fuels. Credit: Phil De Luna, U of T Engineering

When they applied a small electrical bias to the array of nanoneedles, they produced a high electric field at the sharp tips of the needles. This helps attract CO2, speeding up the reduction to CO, with a rate faster than any catalyst previously reported. This represents a breakthrough in selectivity and efficiency which brings CO2 reduction closer to the realm of commercial electrolysers. The team is now working on the next step: skipping the CO and producing more conventional fuels directly.

Their work is published in the journal Nature.

"The field of water-splitting for energy storage has seen rapid advances, especially in the intensity with which these reactions can be performed on a heterogeneous catalyst at low overpotential—now, analogous breakthroughs in the rate of CO2 reduction using renewable electricity are urgently needed," says Michael Graetzel, a professor of physical chemistry at École Polytechnique Fédérale de Lausanne and a world leader in this field. "The University of Toronto team's breakthrough was achieved using a new concept of field-induced reagent concentration."

"Solving global energy challenges needs solutions that cut across many fields," says Sargent. "This work not only provides a new solution to a longstanding problem of CO2 reduction, but opens possibilities for storage of alternative energies such as solar and wind."

Explore further: New step towards producing cheap and efficient renewable fuels

More information: Min Liu et al, Enhanced electrocatalytic CO2 reduction via field-induced reagent concentration, Nature (2016). DOI: 10.1038/nature19060

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6 comments

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Tenstats
2 / 5 (2) Aug 03, 2016
Here we go again. You take CO2 from the atmosphere, convert it to carbon based fuels and then burn the fuel re-emitting the CO2. This does absolutely nothing to reduce the atmospheric CO2 loading. If the conversion process were perfect and required no materials, energy sources that emit carbon as CO2 then a steady state could happen. But going from CO2 to CO requires an energy source (recall that catalysts only lower activation energy but the thermodynamics repain the same).
dnatwork
5 / 5 (3) Aug 03, 2016
@Tenstats Love your cynicism.

They addressed the energy input by saying you could use solar or wind or whatever non-CO2-producing source you want. And you don't have to use up all the resulting fuel. Since CO2 in the atmosphere is a problem, and it is very difficult to capture and sequester it as a gas, then if you could turn it into a liquid, it would be much easier to reinject it into the earth (say, into an old petroleum well).

Also addresses the problem of using the solar and wind that we have--not everything can run on electricity, or if it does you need battery technology that we don't have yet. Transportation being the prime example.
Tenstats
4 / 5 (1) Aug 04, 2016
Wouldn't it be simpler to offset fossil fuel combustion with renewable energy. All the talk about mining CO2 from air is nonsense. One million cubic feet of air at 400 ppm CO2 contains 400 cubic feet of CO2 which equates to about 46 lbs at 1 atm. and 68F. The energy requirements required to make any dent in the atmospheric loading just for handling the gas volume would be (you supply the number). Now lets talk about balance of plant requirements as the energy required to process the materials to construct the chemical plants to produce the CO as well as the downstream chemical plants would be (again anyone with engineering backgrounds can tackle this (maybe Koch, Kellogg, etc.).

I read the paper in Nature. fuel is only mentioned once in the actual paper. The authors did a good job with the physical chemistry, but anyone that would suggest CO2 to fuels has no concept of what it would take to convert to fuels on an industrial scale is simply naive.

KelDude
5 / 5 (1) Aug 07, 2016
@Tenstats It's really easy to be negative. Without these types of investigations, we will definitely burn ourselves off the planet. You have to start somewhere and this is a good beginning. When IBM built the first computers they figured they'd sell a couple of them to a few large businesses because no one else needed or could use them. Now today they are everywhere and look at all the technologies now in use because of that humble beginning. Its the same for this process, give it time, it may save our backsides.
Tenstats
not rated yet Aug 08, 2016
@KelDude My negativity isn't about basic research. In fact the process that they describe might be useful in situations in which the only source of carbon is tied up in, say, carbonate rocks. If water and Heat is available, along with an energy source for electricity, then small amounts of fuel might be generated (forgot, you need O2 as well), plus, say, a skid mounted process plant.
What I object to is grand extrapolations without recognizing the hidden costs for large scale production. I am plagued by my engineer's background (chemical engineering) which demands that both sides of the equation must be balanced.
jamey7788
not rated yet Aug 16, 2016
@KelDude My negativity isn't about basic research. In fact the process that they describe might be useful in situations in which the only source of carbon is tied up in, say, carbonate rocks. If water and Heat is available, along with an energy source for electricity, then small amounts of fuel might be generated (forgot, you need O2 as well), plus, say, a skid mounted process plant.
What I object to is grand extrapolations without recognizing the hidden costs for large scale production. I am plagued by my engineer's background (chemical engineering) which demands that both sides of the equation must be balanced.

Sounds like your describing the George Olah plant in Iceland. They actually make quite a bit of methanol from Co2 with their process.

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