Scientists develop electrified charcoal ‘sponge’ that can soak up CO₂ directly from the air

Researchers have developed a low-cost, energy-efficient method for making materials that can capture carbon dioxide directly from the air.

Researchers from the University of Cambridge used a method similar to charging a battery to instead charge activated charcoal, which is 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 successfully capture CO₂ directly from the air.

The charged charcoal sponge is also potentially more energy efficient than current carbon capture approaches, since it requires much lower temperatures to remove the captured CO₂ so it can be stored. The results are reported in the journal Nature.

“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,” said Dr. Alexander Forse from the Yusuf Hamied Department of Chemistry, who led the research.

“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 sponge-like materials to remove carbon dioxide from the atmosphere, is one potential approach for carbon capture, but current approaches are expensive, require high temperatures and the use of natural gas, and lack stability.

“Some promising work has been done on using porous materials for carbon capture from the atmosphere,” said Forse. “We wanted to see if activated charcoal might be an option, since it’s cheap, stable and made at scale.”

Activated charcoal is used in many purification applications, such as water filters, but normally it can’t capture and hold CO₂ from the air. Forse and his colleagues proposed that if activated charcoal could be charged, like a battery, it could be a suitable material for carbon capture.

When charging a battery, charged ions are inserted into one of the battery’s electrodes. The researchers hypothesized that charging activated charcoal with chemical compounds called hydroxides would make it suitable for carbon capture, since hydroxides form reversible bonds with CO₂.

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