Cambridge researchers develop supercapacitor that absorbs CO2 while it charges

The technology could help speed up carbon capture and storage innovations at much lower costs

Researchers from the University of Cambridge claim to have developed a low-cost supercapacitor that can selectively capture carbon dioxide (CO2) gas while it charges.

The device is about the size of a two-pence coin, according to the researchers, and could help speed up carbon capture and storage innovations at much lower costs.

Around 35 billion tonnes of CO2 are emitted into the atmosphere each year. The most significant challenge that mankind has in its fight against global warming is the build-up of CO2 in the atmosphere.

Unfortunately, the most advanced technologies developed so far for capturing and sequestering CO2 are both energy-intensive and expensive.

The Cambridge researchers say they are tackling this problem by building a supercapacitor that can selectively absorb carbon dioxide as it is being charged. And when this supercapacitor discharges, the CO2 can be released in a controlled way and collected for reuse or disposed of responsibly.

Batteries and traditional electrolytic capacitors are two different types of energy storage devices. However, supercapacitors are a technology that bridges the gap between the two. They have the ability to store much more energy than capacitors and to deliver that energy at greater power outputs than batteries.

Because a supercapacitor depends on electron mobility between electrodes, it degrades more slowly and has a longer lifetime.

These features make them appealing devices for energy storage purpose.

The researchers say their supercapacitor device is made from environmentally friendly components. Its electrodes are comprised of carbon derived from coconut shells, while seawater is used as the electrolyte.

The device consists of two electrodes of positive and negative charge.

In the experiments, the researchers tried alternating from a negative to a positive voltage to increase the charging duration from previous experiments, which boosted the supercapacitor's ability to capture carbon.

"We found that that by slowly alternating the current between the plates we can capture double the amount of CO2 than before," said Dr Alexander Forse from Cambridge's Yusuf Hamied Department of Chemistry, who led the research.

"The charging-discharging process of our supercapacitor potentially uses less energy than the amine heating process used in industry now," he added.

Their next step will be to research and optimise the exact mechanism of CO2 collection.

"Then it will be a question of scaling up."

Dr Israel Temprano, a co-author of the paper, was involved in creating a gas analysis technique for the device, to study the process of CO2 adsorption.

"This field of research is very new, so the precise mechanism working inside the supercapacitor still isn't known," he said.

Co-author Grace Mapstone said that while supercapacitors can't hold as much charge as batteries, they would prioritise supercapacitors while developing a technology for carbon capture because of their "durability".

"The best part is that the materials used to make supercapacitors are cheap and abundant. The electrodes are made of carbon, which comes from waste coconut shells," Mapstone added.

Potentially, devices based on this technology could be used to power carbon capture and storage systems at much lower cost.

The detailed findings of the study are published in the journal Nanoscale.

The scientific community is currently working on a variety of new techniques that can help remove excess CO2 from the environment.

In 2019, an international team of scientists led by RMIT University in Melbourne said they discovered a technique to convert carbon dioxide (CO2) gas into solid carbon.

The researchers said their technique uses a liquid alloy to turn CO2 into carbon particles, thus providing an alternative pathway for removing the greenhouse gas from the atmosphere.