Scientists Describe Device That Captures Carbon-Dioxide While Charging, Then Releases It In Controlled Way While Discharging

The supercapacitor device is similar to a rechargeable battery, is the size of a two-pence coin, and is made in part from sustainable materials including coconut shells and seawater.

The negative plate of the supercapacitor draws on carbon-dioxide when the electrodes become charged, and ignores other emissions such as oxygen, nitrogen, and water. Through this method, the supercapacitor both captures carbon and stores energy. | Representative Photo

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New Delhi: Scientists from the University of Cambridge, England, have developed a low-cost battery-like device which can selectively capture carbon-dioxide gas while charging, and release it in a controlled way while discharging. The carbon-dioxide gas can then be collected to be reused or disposed off responsibly. 

The study describing the device was recently published in the journal Nanoscale. 

How Does The Supercapacitor Device Work?

The supercapacitor device is similar to a rechargeable battery, is the size of a two-pence coin, and is made in part from sustainable materials including coconut shells and seawater, the study said. The device could help power carbon capture and storage technologies at much lower cost. 

Solutions are urgently needed to eliminate the emission of around 35 billion tonnes of carbon-dioxide into the atmosphere annually, and to address the climate crisis. The most advanced carbon capture technologies which are currently in use require large amounts of energy and are expensive. 

According to the study, the supercapacitor device consists of two electrodes of positive and negative charge. The researchers, as part of the new study, tried alternating from a negative to a positive voltage to extend the charging time from previous experiments, improving the supercapacitor's ability to capture carbon. 

In a statement released by University of Cambridge, Dr Alexander Forse, who led the research, said the scientists found that by slowly alternating the current between the plates, they can capture double the amount of carbon-dioxide than before. He added that the charging-discharging process of the supercapacitor potentially uses less energy than the amine heating process used in industry now. He further said the team's next questions will involve investigating the precise mechanisms of carbon-dioxide capture and improving them, following which it will be a question of scaling up. 

How Is The Supercapacitor Better Than A Rechargeable Battery?

Though a supercapacitor is similar to a rechargeable battery, the main difference is in how the two devices store charge. While a battery uses chemical reactions to store and release charge, a supercapacitor does not rely on chemical reactions, but on the movement of electrons between electrodes. As a result, it takes longer to degrade and has a longer lifespan. 

In the same statement, Grace Mapstone, who co-authored the study, said the trade-off is that supercapacitors cannot store as much charge as batteries, but for something like carbon capture, one would prioritise durability. She added that the best part is that the materials used to make supercapacitors are cheap and abundant. For instance, the electrodes are made of carbon, which comes from waste coconut shells. 

Mapstone said the researchers want to use materials that are inert, that do not harm environments, and which need to be disposed off less frequently. For example, the carbon-dioxide dissolves into a water-based electrolyte which is basically seawater, she added.

The Supercapacitor Does Not Absorb Carbon-Dioxide Spontaneously

However, the supercapacitor does not absorb carbon-dioxide spontaneously; rather, it must be charging to draw in the gas, the study said. The negative plate draws on carbon-dioxide when the electrodes become charged, and ignores other emissions such as oxygen, nitrogen, and water, which do not contribute to climate change. Through this method, the supercapacitor both captures carbon and stores energy.

Dr Israel Temprano, one of the co-authors of the study, contributed to the research by developing a gas analysis technique for the device, which uses a pressure sensor that responds to changes in gas adsorption in the electrochemical device. Therefore, the sensor helps narrow down the precise mechanism at play inside the supercapacitor when the carbon-dioxide is absorbed and released. Before scaling up the supercapacitor, it is important to understand these mechanisms, the possible losses, and the routes of degradation. 

Temprano said this friend of research is very new so the precise mechanism working inside the supercapacitor is still not known.