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Carbon capture’s ‘Goldilocks problem’

Researchers from UNSW are using NCI’s supercomputer to pinpoint the ‘sweet spot’ of new carbon capture materials.Sean Smith diagram_electrocatalytic CO2 capture-release boron nitride

Current materials for capturing carbon from power plant exhaust tend to bind CO2 too effectively. This causes
problems when the carbon needs to be released again for sequestration or recycling.

“If the material binds to CO2 too strongly, which is the basic problem with current materials, then you have to heat them up to a high temperature to pull the CO2 off, and that costs money,” explains chief investigator Professor Sean Smith.

“It’s a ‘Goldilocks problem’.”

Professor Smith and his team are taking a novel approach to the search for new materials. They have identified several materials that adopt altered binding behaviour when exposed to electrical charge.

“Normally, if you put CO2 in contact with these materials there is very weak binding – they won’t capture CO2 at all. But if you put an electrical charge on the material, suddenly it binds CO2 quite effectively,” says Professor Smith. “And if you then remove the charge, it lets the CO2 go.”

The result is a material that can be ‘switched’ on and off with an electrical charge, side-stepping the expensive heating requirements of current industry materials.

However, these new charge-responsive materials come with a hurdle of their own.

“One of the materials we’re looking at now, for example, is boron nitride, which is a semiconductor with a very large bandgap. That means it takes a lot of voltage to put enough charge on, and there is a cost to that,” says Professor Smith.

“What we’re using NCI to do is search for materials that have a similar capacity to bind CO2 but with a much smaller bandgap.”

The team is running first principles and electronic structure calculations on Raijin to work out exactly how each new material interacts with CO2, predicting the binding strength and voltage response profile to pinpoint a material with ideally balanced properties.

“These are very numerically intensive calculations, which demands that we have access to a facility of the order of capability that the NCI has,” explains Professor Smith.

“There is no other way you can do this work.”

UNSW

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