Jul 15, 2019 | Updated: 10:46 AM EDT

Super-absorbent fake leaves suck carbon dioxide from the environment

Feb 13, 2019 09:45 AM EST

Photosynthetic Process
(Photo : By At09kg - Own work, CC BY-SA 3.0,)

Plants undergo photosynthesis is the process of converting water and carbon dioxide to produce carbohydrates and oxygen using the sun's energy. This process is mimicked by fake leaves that have great potential in carbon dioxide reduction from the atmosphere. However, the current limitation involves the whole process workable only in laboratories. 

ACS Sustainable Chemistry & Engineering Journal published a design solution proposed by the University of Illinois at Chicago researchers that could place these fake leaves into the real world and not just in the lab. Their designed leaf is said to be at least ten times more efficient in carbon dioxide conversion compared to natural leaves. 

"So far, all designs for artificial leaves that have been tested in the lab use carbon dioxide from pressurized tanks. In order to implement successfully in the real world, these devices need to be able to draw carbon dioxide from much more dilute sources, such as air and flue gas, which is the gas given off by coal-burning power plants," said Meenesh Singh, assistant professor of chemical engineering in the UIC College of Engineering and corresponding author on the paper.

How it works

These fake leaves need to be supplied with carbon dioxide from the air in order to start an artificial photosynthetic reaction as the supply for pressurized carbon dioxide is cut off. 

A semi-permeable membrane of quaternary ammonium resin filled with water consists of the transparent capsule that encapsulates a traditional fake leaf. This design was conceptualized by Singh and his graduate student Aditya Prajapati. Water evaporates when exposed to sunlight. Water absorbs carbon dioxide from the air as it moves out of the membrane. The artificial photosynthetic reactions occur in a unit comprised of a light absorber with catalysts that harness conversion of carbon dioxide into carbon monoxide. Synthetic fuels can be drawn out from the siphoned carbon monoxide. Oxygen is also a by-product that can be released or collected. 

"By enveloping traditional artificial leaf technology inside this specialized membrane, the whole unit is able to function outside, like a natural leaf," Singh said.

Carbon dioxide levels can be reduced by 10 percent through  360 1.7-meter by 0.2- meter leaves placed in a 500-meter square area. This would be efficient within 100 meters of the array in a day based on calculations of Singh and Prajapati. 

"Our conceptual design uses readily available materials and technology, that when combined can produce an artificial leaf that is ready to be deployed outside the lab where it can play a significant role in reducing greenhouse gases in the atmosphere," Singh said.

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