Artificial, bio-inspired sheet. Carbon dioxide (red and black balls) enter the leaves as the water (white and red balls) evaporates from the bottom of the leaves. An artificial photo system (a foil-lilac circle) made of a cathode-coated light absorber turns carbon dioxide into carbon monoxide and converts water into oxygen (shown as a double red ball) using sunlight. Sincerely, Meenesh Singh.
Artificial leaves imitate photosynthesis – the process where plants use water and carbon dioxide from the air to produce carbohydrates using sun energy. But even the most up-to-date artificial leaves that promise to reduce carbon dioxide from the atmosphere work only in the lab because they use pure carbon dioxide under pressure from reservoirs.
But now researchers at the University of Illinois in Chicago have proposed a design solution that could remove the artificial leaves from the lab and into the environment. Their improved leaf, which would use carbon dioxide – a powerful greenhouse gas – from the air would be at least 10 times more effective than natural leaves in converting carbon dioxide into fuel. Their findings are reported in ACS Sustainable Chemistry & Engineering.
"So far, all artificial leaf designs that have been tested in the laboratory use carbon dioxide from pressure tanks. To be successful in the real world, these devices must be able to attract carbon dioxide from much more diluted sources such as air and flue gas, which is the gas generated by coal-fired power plants, "said Meenesh Singh, associate professor chemical engineering at UIC Engineering College and author-author of the article.
Removing the carbon dioxide under pressure from these leaves means they need to have a way to collect and concentrate carbon dioxide from the air to manage their artificial photosynthetic reactions.
Singh and his colleague Aditya Prajapati, a student in his laboratory, have solved this problem by encapsulating a traditional artificial sheet inside a transparent capsule made of a semi-permeable quaternary ammonium resin membrane and filled with water. The membrane allows the water inside to evaporate when warmed by sunlight. When water passes through the membrane, it selectively extracts carbon dioxide from the air. The artificial photosynthetic unit inside the capsule is composed of a light absorber coated with catalysts that convert carbon dioxide into carbon monoxide that can be drained and used as the basis for the production of various synthetic fuels. Oxygen is also produced and can be collected or released into the environment.
"By embracing the traditional technology of artificial sheets inside this specialized membrane, the whole unit can function as a natural leaf," Singh said.
According to their calculations, 360 sheets, each 1.7 m long and 0.2 m wide, will produce almost half a ton of carbon monoxide per day, which can be used as a base for synthetic fuels. Three hundred and sixty of these artificial leaves, covering an area of 500 meters, could reduce the levels of carbon dioxide by 10% in the ambient air within 100 meters of the massif for one day.
"Our conceptual design uses easily accessible materials and technologies that, when combined, can produce an artificial sheet that is ready to be deployed outside the laboratory where it can play an important role in reducing greenhouse gases in the atmosphere," Singh said.
This article is reissued by materials provided by the University of Illinois in Chicago. Note: The material may have been edited for length and content. For more information, please contact the quoted source.
Evaluation of Artificial Photosynthetic Systems for Integrated Carbon Capture and Transformation. Aditya Prajapati and Mines R. Singh. ACS Sustainable Chem. Eng., DOI: 10.1021 / acssuschemeng.8b04969.