Synthesis of Planet‐Like Liquid Metal Nanodroplets with Promising Properties for Catalysis

Abstract Liquid metal nanodroplets are an emerging class of underexplored materials with significant potential in many applications, including catalysis, bio‐therapeutics, and phase‐change materials. These nanostructures are generally synthesized by mechanical agitation via ultrasonication of low‐melting metals like Ga. Once these materials are successfully synthesized, they can be suspended in a vast array of different solvents. However, one major issue arises specifically with liquid metal alloys which are found to de‐alloy in the sonication process. Here, it is demonstrated that this challenge can be overcome by undertaking sonication at high temperatures, suspending nanodroplets within molten sodium acetate (NaOAc). After cooling, the nanostructures become planet‐like nanodroplets which are covered by an interfacial oxide crust, feature a liquid metal mantle, and a solid core. The molten salt solvent can effectively be removed rendering this approach to be ideal, especially for catalysts. The proof‐of‐concept application is demonstrated by carrying out electrocatalytic ethanol oxidation, using the Cu–Ga system. The superior performance of the Cu–Ga nanodroplets highlights potential in catalyzing a vast array of reactions. Aside from the Cu–Ga system, this facile process can be applied to multiple other systems, including Ag–Ga, Zn–Ga, Bi–Ga, In–Cu, and Sn–Cu.