Homogenization of Post‐Transition Metal Alloys into High‐Entropy‐Like Nanoparticles

Abstract Presently, the most common high‐entropy systems are formed from the mixing of immiscible transition metals under extreme conditions. Here, a new class of high‐entropy‐like nanoparticles is reported, based entirely on post‐transition metals, Ga, In, Sn, Zn, and Bi, which undergo core‐level nanoscale homogenization via low‐temperature sonication. Starting from a bulk high‐entropy‐like melt, with clear phase segregation, including Ga‐rich, Zn‐rich, and Bi‐rich domains, ultrasonic agitation is applied to disrupt their immiscibility. The resulting cavitation and shear forces promote rapid mixing and atomic‐level diffusion, forming uniformly distributed high‐entropy‐like, compositionally complex nanoparticles with a core‐shell structure. When applied for electrochemical carbon dioxide reduction, the nanoparticles exhibit high current densities with a selectivity toward formates. The finding demonstrates a scalable route to high‐entropy‐like nanoparticles derived from post‐transition metals, circumventing the need for high‐temperature or shock‐based synthesis, while also expanding the compositional space into softer, low‐melting‐point systems.