Researchers around the globe have been trying to create sustainable fuels by mimicking the natural process of photosynthesis. After all, if plants can use sunlight to transform carbon dioxide into hydrocarbons, why can’t we? In the latest development, a team of scientists from the Energy Department’s Lawrence Berkeley National Laboratory has figured out a way to convert CO2 directly into ethanol and ethylene, using a process powered by solar energy.
To put it another way, the team made corn ethanol, except they skipped all the steps that involve planting corn, growing it, harvesting it, and processing it into biofuel. To ice the sustainability cake, the new system could pair up with power plants and other industrial facilities to capture greenhouse gases at the source.
So…how’d they do that?
Yes, We Can: Fuel From Sunlight And CO2
The sustainable ethanol breakthrough is especially significant because, according to Berkeley Lab, it’s the first time that researchers have been able to convert CO2 directly into a usable target fuel, rather than into various carbon-based fuel precursors or building blocks.
That’s no small feat considering that plants have had a few million years or so to fine tune photosynthesis. In comparison, modern science has only been around for a blink of an eye.
To obtain the desired result, the researchers picked apart every feature of the conventional photoelectrochemcial process and customized it for optimal performance (photoelectrochemical refers to a solar cell that stimulates a chemical reaction with a jolt of electricity, such as “splitting” water to produce hydrogen):
Among the new components developed by the researchers are a copper-silver nanocoral cathode, which reduces the carbon dioxide to hydrocarbons and oxygenates, and an iridium oxide nanotube anode, which oxidizes the water and creates oxygen.
The result is an energy efficient system that can reduce CO2 to ethanol or ethylene with only about 2.5 volts of electricity, compared to conventional systems that require 5 volts.
The new system can work efficiently throughout the day, not just during peak brightness.
There are many next steps before a system like this appears at your local power plant, so stay tuned for more.
There They Go Again: #ThanksObama
Not for nothing but this makes the second time in recent days that the Energy Department has trolled President* Trump, by emphasizing the Obama-era origins of successful renewable energy initiatives.
Here’s Berkeley Lab on Monday, enthusing over the Obama initiative that provided the platform for its new artificial research:
That sun-to-fuel path is among the key goals of the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub established in 2010 to advance solar fuel research…
The initial focus of JCAP research was tackling the efficient splitting of water in the photosynthesis process. Having largely achieved that task using several types of devices, JCAP scientists doing solar-driven carbon dioxide reduction began setting their sights on achieving efficiencies similar to those demonstrated for water splitting, considered by many to be the next big challenge in artificial photosynthesis.
Last week the Energy Department also emphasized the Obama-era origins of the SunShot initiative, which just achieved its goal for utility scale solar three years early. SunShot will continue to invest taxpayer dollars in lowering the cost of solar power, but now it will pivot to focus more attention on grid resiliency — a timely move considering this year’s hurricane season.
But Wait, There’s More!
Where were we? Oh right, Berkeley Lab.
This has been a really good week for Berkeley Lab.
Berkeley Lab announced its CO2-to-fuel findings on Monday, and on the same day it also announced another new study focused more narrowly on beefing up the electrocatalyst used in artificial photosynthesis.
The other study involved a new catalyst made of nanoscale copper spheres, which fuse into cube-like structures shortly after electrolysis begins.
Scientists are still not sure why that transition enhances fuel production, but they tried skipping over the sphere stage and starting with a cube structure, and it wasn’t as efficient. Here’s research team leader Peidong Yang with an explainer:
“What we know is that this unique structure provides a beneficial chemical environment for CO2 conversion to multicarbon products,” he said. “The cube-like shapes and associated interface may be providing an ideal meeting place where the carbon dioxide, water, and electrons can come together.”
Got all that?
For more details, check out the lab’s paper published in the Proceedings of the National Academy of Sciences under the title, “Copper nanoparticle ensembles for selective electroreduction of CO2 to C2–C3 products.“
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Image: “Schematic of a solar-powered electrolysis cell which converts carbon dioxide into hydrocarbon and oxygenate products with an efficiency far higher than natural photosynthesis. Power-matching electronics allow the system to operate over a range of sun conditions” by Clarissa Towle/Berkeley Lab.