Liquid Gallium Shown to Break Down Carbon Dioxide

A team of researchers led by the University of New South Wales has discovered that suspensions of gallium liquid metal — a soft, silvery-white metal that is solid at room temperature but it can melt in the palm of your hand (it has a low melting point of 29.76 degrees Celsius, or 85.57 degrees Fahrenheit) — can convert carbon dioxide (CO2) into carbonaceous solid products and oxygen (O2) at near room temperature.

Liquid gallium converts carbon dioxide into oxygen and a high-value solid carbon product. Image credit: Tang et al., doi: 10.1002/adma.202105789.

“We see very strong industrial applications with regards to decarbonization,” said first author Junma Tang, a researcher in the School of Chemical Engineering at the University of New South Wales.

“This technology offers an unprecedented process for capturing and converting carbon dioxide at an exceptionally competitive cost.”

“The applications could be in cars to convert polluting exhaust gases, or even at a much larger scale at industrial sites where carbon dioxide emissions could be immediately captured and processed using this technology.”

“We have already scaled this system up to 2.5 liters dimensions, which can deal with around 0.1 liter of carbon dioxide per minute.”

“And we’ve tested that running continuously for a whole month and the efficiency of the system did not degrade.”

The process dissolves captured carbon dioxide gas into a solvent around nanoparticles of gallium. The reactor also contains nano-sized solid silver rods that are the key to generating the triboelectrochemical reactions that take place once mechanical energy (e.g. stirring/mixing) is introduced.

A triboelectrochemical reaction occurs in solid–liquid interfaces due to friction between the two surfaces, with an electric field also created that sparks a chemical reaction.

The reactions break the carbon dioxide into oxygen gas, as well as carbonaceous sheets which ‘float’ to the surface of the container due to differences in density and can therefore be easily extracted.

The scientists obtained 92% efficiency at the remarkably low input energy of 230 kWh for the capture and conversion of a ton of carbon dioxide.

They estimate this equates to a cost of around $100 per ton of carbon dioxide.

“This is a very green process which also produces a high-value carbonaceous sheet which can then be sold and used to make electrodes in batteries, or for carbon fiber materials that are used in high-performance products like aircraft, racing cars, and luxury vehicles,” said Paul Butler, director of LM Plus.

“What we are working towards now is to raise funds to build a larger size proof-of-concept for this system to work within a 12-m (40-foot) container that could ultimately help industrial sites immediately capture any carbon dioxide emissions and convert them.”

The team’s paper was published in the journal Advanced Materials.

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Junma Tang et al. Liquid metal-enabled Mechanical energy-induced CO2 Conversion. Advanced Materials, published online October 6, 2021; doi: 10.1002/adma.202105789

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