Gallium (Ga), sitting below aluminum (Al) and to the right of zinc (Zn) in the periodic table, has the atomic number 31. It has a density of 5.91 g/cm3, and has a boiling point of 2,229 °C (4,044 °F). What’s most striking about the odd metal, however, is its melting point: this particular metal melts at a measly 29.76 °C (85.58 °F), meaning any person can reasonably melt solid gallium into liquid form just by the heat of their own body.
Now, while the prospect of a metal that melts at the slightest human touch sounds like it doesn’t have much going for it, an international team of scientists led by the University of New South Wales (UNSW) begs to differ: for them, gallium can easily be part of our collective greener future.
The international effort, led by Prof. Kourosh Kalantar-Zadeh, has resulted in a remarkable proof-of-concept showing that liquid gallium can aid in carbon dioxide (CO2) decomposition when used in a suspension. The study by Kalantar-Zadeh and team was published in the journal Advanced Materials.
The system consists of beads of liquid gallium—”nanoparticles,” really—suspended in a solvent. The suspension also contains silver (Ag) nanorods; the silver nanorods interact with the gallium nanoparticles and create a triboelectric effect. (This wouldn’t be the first time we’ve encountered this effect before; read further about these “nanogenerator” wooden floorings to learn more about the triboelectric effect.)
The electricity from the triboelectric interactions between nanoparticles and nanorods kickstart an electrochemical reaction, decomposing the CO2 gas entering through an inlet. The oxygen gas (O2) product escapes through the outlet valve, while the carbon (C) product forms into “flakes” on the surface of the gallium nanoparticles. At this point, the sonication bath vibrates the flakes out of the surface of the liquid gallium beads, floating to the surface as a thin layer of carbon flakes. The gallium beads are then made available for further reaction.
Said Junma Tang, a researcher in the School of Chemical Engineering at UNSW: “We have already scaled this system up to 2.5-L dimensions, which can deal with around 0.1 L 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 team estimates that an input energy of 230 kWh can convert a ton of CO2 with 92% efficiency, equating to around US$100 per ton of CO2. Tang followed: “We see very strong industrial applications with regards to decarbonization. […] This technology offers an unprecedented process for capturing and converting carbon dioxide at an exceptionally competitive cost.”
Tang and team believe that applications for their novel CO2 decomposition method can range from converting automobile exhaust to carbon capture technology. To commercialize the research, UNSW established the liquid metal technology company LM Plus with help from its Knowledge Exchange program, together with seed investment from Australian venture fund Uniseed.
Said LM Plus director Paul Butler: “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. […] 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-ft) container that could ultimately help industrial sites immediately capture any carbon dioxide emissions and convert them.”
LM Plus hopes to finish the said new project within 15 months, and has already secured funding from potential commercial partners.
References
- Martin, N. (2021, October 13). Liquid metal proven to be cheap and efficient CO2 converter [Text]. UNSW Newsroom. https://newsroom.unsw.edu.au/news/science-tech/liquid-metal-proven-be-cheap-and-efficient-co2-converter
- Periodic Table. (n.d.). Gallium—Element information, properties and uses. Periodic Table. Retrieved October 14, 2021, from https://www.rsc.org/periodic-table/element/31/gallium
- Sci-News. (2021, October 13). Liquid Gallium Shown to Break Down Carbon Dioxide. Sci-News. http://www.sci-news.com/othersciences/chemistry/liquid-gallium-carbon-dioxide-conversion-10164.html
- Tang, J., Tang, J., Mayyas, M., Ghasemian, M. B., Sun, J., Rahim, M. A., Yang, J., Han, J., Lawes, D. J., Jalili, R., Daeneke, T., Cao, Z., Echeverria, C. A., Allioux, F.-M., Zavabeti, A., Hamilton, J., Mitchell, V., O’Mullane, A. P., Kaner, R. B., … Kalantar-Zadeh, K. (n.d.). Liquid metal-enabled Mechanical energy-induced CO2 Conversion. Advanced Materials, n/a(n/a), 2105789. https://doi.org/10.1002/adma.202105789
