The team built an electrode using metallic crystals capable of efficiently producing hydrogen from water. These crystals, grown in liquid metals such as Gallium, are being investigated for potential uses in quantum computing and hydrogen extraction technologies.

Gallium, a metal that remains solid at room temperature but shifts to liquid at higher temperatures, was key to this study. The researchers faced the challenge of visualizing crystal formation within Gallium, whose opacity prevents conventional microscopy from working. Professor Kourosh Kalantar-Zadeh led the group in developing an approach that allows X-rays to reveal detailed internal views of the metallic crystals.

Using X-ray computed tomography, typically a medical imaging tool, the scientists constructed three-dimensional models of platinum crystals as they emerged inside cooling droplets of a platinum-Gallium alloy. The technique revealed distinctive rod-like and frost-like crystal structures developing over time. PhD student Ms Moonika Widjajana noted, "This study illustrated how X-ray computed tomography can overcome the challenge of observing crystal growth within liquid metal - an opaque material that is usually impossible to penetrate with light and electrons."

The contradictory properties of liquid metals, which combine aspects of solids and liquids, make them valuable for research in material science. Professor Kalantar-Zadeh's group specializes in pushing the chemical boundaries of liquid metals to create catalysts for more efficient chemical reactions. According to the professor, "Liquid metals are also very good solvents, with a powerful ability to dissolve other metallic elements, like sugar in water." When excess metallic elements are present, crystals begin to grow in a manner comparable to the formation of sugar crystals in supersaturated water.

The study involved dissolving platinum beads in Gallium or a Gallium-indium solution at 500 degrees Celsius, following which the mixture was cooled to initiate crystal formation. X-ray tomography allowed mapping of the crystal growth process, demonstrating how tiny rods rapidly formed within the alloy as it cooled.

Imaging resolution currently limits the level of detail obtained, but improvements in tomography are expected to provide deeper insights into metallic crystal growth in the future.

Research Report: Observing growth of metallic crystals inside liquid metal solvents

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