Facile Solvothermal Synthesis of Pt–Ir–Pd–Rh–Ru–Cu–Ni–Co High-Entropy Alloy Nanoparticles

High-entropy alloys (HEAs) present a promising class of materials due to extraordinary properties and vast possibilities for tailoring product characteristics through changes in stoichiometry. Nanosized HEAs are especially interesting with respect to catalysis of multistep reactions and replacement of scarce, expensive, and/or toxic elements. Finding suitable methods for the synthesis of nano-HEAs remains a severe challenge, and typical methods are limited in productivity, compatibility of different elements, substrate types, and/or specialized laboratory equipment. Here, we report a simple solvothermal method for the synthesis of eight-component Pt-Ir-Pd-Rh-Ru-Cu-Ni-Co HEA nanoparticles with a high potential production capacity. The method relies on simple autoclaves heated to a moderate temperature. In situ X-ray scattering experiments show that the individual metal components form from one-element precursors at higher reaction temperatures, suggesting that the formation is auto-catalyzed, that is, the particles catalyze their own growth, in correspondence with previous findings for a five element (Pt-Ir-Rh-Pd-Ru) noble-metal HEA. This paper extends the method to cheaper and more abundant 3d metals (Co, Ni, and Cu) despite the differences in atomic radii and chemical reactivity and thereby adds significantly to the synthetic chemistry and understanding of HEA nanomaterials.