Is liquid metal a key to carbon capture?

What if the key to solving the carbon dioxide emissions challenge is the soft, silvery element named Gallium?

A research team at the Royal Melbourne Institute of Technology discovered that passing carbon dioxide through a gallium-indium alloy caused the gas to split into "useful reaction products", as reported by the American Society of Mechanical Engineers (ASME).

“The gallium gets oxidised, and we get carbon flakes—solid flakes—sort of floating on the surface,” Karma Zuraiqi, a researcher at the university and lead author of the paper Direct conversion of CO₂ to solid carbon by Ga-based liquid metals, published in Energy & Environmental Science, told the ASME.

“It’s a black powder, which looks sort of like ash, sitting on top of the liquid metal."

Found in trace amounts in compounds like bauxite and zinc ores, gallium is used primarily in electronics. Like mercury, it is a metal that is a liquid at, or near normal room temperatures.

However, it expands when it solidifies, like water does when it becomes ice. Indium was used to ensure the alloy remained liquid at room temperature should it unintentionally drop below 30 degrees Celsius, according to the researchers.

Carbon is insoluble in gallium and the elements are different densities, making retrieval of the carbon easier, the ASME report noted, adding that it also provides a simpler way to store CO₂.

It is still early days for the technology as the research was proof of concept, with researchers looking to scale the process up from to a shipping container-sized modular reactor.