Researchers have developed an inexpensive device that can selectively capture carbon dioxide as it recharges. Then, as it discharges, the CO2 can be released in a controlled manner and collected for reuse or responsible disposal.
The supercapacitor device, which looks like a rechargeable battery, is about the size of a quart and is made in part from sustainable materials including coconut shells and seawater.
“We have found that by slowly alternating the current between the plates, we can capture twice the amount of CO2 than before.” — Dr. Alexander Forse
Designed by scientists at the University of Cambridge, the supercapacitor could help power carbon capture and storage technologies at a much cheaper cost. Every year, around 35 billion tonnes of CO2 are released into the atmosphere, and solutions are urgently needed to eliminate these emissions and tackle the climate crisis. Today’s most advanced carbon capture technologies are quite expensive and require large amounts of energy.
The supercapacitor consists of two electrodes with positive and negative charge. In work led by Trevor Binford while completing his Masters at Cambridge, the team tried to alternate from negative voltage to positive voltage to extend the charging time of previous experiments. This improved the supercapacitor’s ability to capture carbon.
“We have found that by slowly alternating the current between the plates, we can capture double the amount of CO2 than before,” said Dr Alexander Forse of Cambridge’s Yusuf Hamied Department of Chemistry, who led the research. .
“Our supercapacitor’s charge-discharge process potentially uses less energy than the amine heating process currently used in industry,” Forse said. “Our next questions will be to study the precise mechanisms of CO2 capture and to improve them. Then, it will be a question of scaling up. »
The results were published on May 19, 2022 in the journal At the nanoscale.
A supercapacitor is similar to a rechargeable battery, but the main difference is how the two devices store charge. A battery uses chemical reactions to store and release charge, whereas a supercapacitor does not rely on chemical reactions. Instead, it relies on the movement of electrons between electrodes, so it takes longer to degrade and has a longer lifespan.
“The tradeoff is that supercapacitors can’t store as much charge as batteries, but for something like carbon capture, we would prioritize durability,” said co-author Grace Mapstone. “The best part is that the materials used to make supercapacitors are cheap and plentiful. The electrodes are made of carbon, which comes from waste coconut shells.
“We want to use inert materials, which do not harm the environment and which we have to dispose of less frequently. For example, CO2 dissolves in a water-based electrolyte which is essentially seawater.”
However, this supercapacitor does not absorb CO2 spontaneously: it must be charging to draw CO2. As the electrodes charge, the negative plate draws in CO2 gas, while ignoring other emissions, such as oxygen, nitrogen and water, which do not contribute to climate change. Using this method, the supercapacitor both captures carbon and stores energy.
Co-author Dr. Israel Temprano contributed to the project by developing a gas analysis technique for the device. The technique uses a pressure sensor that responds to changes in gas adsorption in the electrochemical device. The results of Temprano’s contribution help refine the precise mechanism at play inside the supercapacitor when CO2 is absorbed and released. Understanding these mechanisms, possible losses, and degradation pathways are all essential before the supercapacitor can be scaled up.
“This area of research is very new, so the precise mechanism operating inside the supercapacitor is still not known,” Temprano said.
Reference: “Enhancing the capacity of supercapacitive swing adsorption CO2 capture by tuning Charging Protocols” by Trevor B Binford, Grace Mapstone, Israel Temprano and Alexander C. Forse, May 19, 2022, At the nanoscale.
The research was funded by a Future Leaders Fellowship at Dr Forse, a UK research and innovation program developing the next wave of world-class research and innovation.