Electrified ‘sponge’ material can absorb CO2 directly from the air

The method, which the researcher said is similar to charging a battery, charges activated charcoal often used in household water filters.

By charging the charcoal ‘sponge’ with ions that form reversible bonds with CO2, the researchers found the charged material could capture CO2 directly from the air.

“Capturing carbon emissions from the atmosphere is a last resort, but given the scale of the climate emergency, it’s something we need to investigate,” lead researcher Dr Alexander Forse from the Yusuf Hamied Department of Chemistry said in a statement.

“The first and most urgent thing we’ve got to do is reduce carbon emissions worldwide, but greenhouse gas removal is also thought to be necessary to achieve net zero emissions and limit the worst effects of climate change. Realistically, we’ve got to do everything we can.”

Direct air capture, which uses porous materials to remove carbon dioxide from the atmosphere, is one potential approach for carbon capture, but the researchers said that current approaches are expensive, require high temperatures and the use of natural gas, and lack stability.

The researchers hypothesised that charging activated charcoal with hydroxides would make it suitable for carbon capture, since hydroxides form reversible bonds with CO2.

The Cambridge team used a battery-like charging process to charge an inexpensive activated charcoal cloth with hydroxide ions. In this process, the cloth acts like an electrode in a battery, and hydroxide ions accumulate in the pores of the charcoal. At the end of the charging process, the charcoal is removed from the ‘battery’, washed and dried.

Tests of the charged charcoal sponge showed that it could capture CO2 directly from the air, due to the bonding mechanism of the hydroxides.

Additionally, to collect the  CO2 from the charcoal so it can be purified and stored, the material is heated to reverse the hydroxide-CO2 bonds. According to the researchers, most materials currently used for CO2 capture from air need to be heated to temperatures as high as 900°C, often using natural gas.

The charged charcoal sponges developed by the Cambridge team requires heating to 90-100°C, temperatures that can be achieved using renewable electricity. The materials are also heated through resistive heating, which heats them from the inside out, making the process faster and less energy-intensive.

“We are working now to increase the quantity of carbon dioxide that can be captured, and in particular under humid conditions where our performance decreases,” said Forse. ““This approach opens a door to making all kinds of materials for different applications, in a way that’s simple and energy-efficient.”

A patent has been filed and the research is being commercialised with the support of Cambridge Enterprise, the University’s commercialisation arm.

The research – supported by the Leverhulme Trust, the Royal Society, the Engineering and Physical Sciences Research Council (EPSRC), and the Centre for Climate Repair at Cambridge – can be read in full here.

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