Homogenization of Post-Transition Metal Alloys into High-Entropy-Like Nanoparticles.

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.